WO2013087804A1

WO2013087804A1 - Improvements in and relating to electroosmotic pumps

Info

Publication number: WO2013087804A1
Application number: PCT/EP2012/075469
Authority: WO
Inventors: Christopher M. Puleo; Christopher Fred Keimel; Xiaohui Chen; Ralf Lenigk; Craig Patrick GALLIGAN; Todd Frederick MILLER
Original assignee: General Electric Company; Ge Healthcare Uk Limited
Priority date: 2011-12-15
Filing date: 2012-12-13
Publication date: 2013-06-20
Also published as: EP2791506A1

Abstract

An electroosmotic pump comprises a plurality of membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes, a plurality of electrodes comprising cathodes and anodes, and a power source. Each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternately and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on other side of the membrane. At least one of the cathodes or anodes is disposed between a postive electroosmotic membrane and negative electroosmotic membrane. The pump can be used to actuate a valve, or can be precharged, duch that an external power source is not required.

Description

Improvements in and relating to electroosmotic pumps

FIELD

[0001] The invention relates to a non-mechanical pump, and more particularly to an electroosmotic pump (EOP) that generates high pressure using comparatively lower voltage. The invention is further associated with: methods for making and using an EOP; with the use of a high pressure EOP for self-contained actuation of mechanical valves and control components; and with an EOP which is independent of an external power source.

BACKGROUND

[0002] Pumps can be classified into mechanical and non-mechanical varieties. Generally, the conventional mechanical pumps have issues with reliability of the moving pump- components. Electrokinetic pumps, on the other hand, contain no moving parts, making them suitable for a variety of applications, including fluid movement in microanalytical systems. EOPs are one of the most represented class of these pumps, and provide fluid flow due to movement of an electric double layer that forms at the solid-liquid interface. Application of an electric field across a porous membrane structure of an EOP results in a movement of the electric double layer, which results viscous drag. The viscous drag then causes bulk fluid flow and generation of a net pressure.

[0003] Standard EOPs made from a ceramic frit or packed capillaries require over 1 kV to establish the electric fields required for pumping. The electric field is generated using at least two electrodes disposed on either side of the porous membrane and an external power source. Generally, the current from the electrode is passed into the pumping solution via chemical reactions at the electrode surface, e.g. using a Pt electrode and water as the pumping solution to produce gases like hydrogen or oxygen, which may stall the pump. Alternative electrode materials are used in electrokinetic pumps, such as redox polymers, redox metal salts or oxides. Alternative thin porous substrates have, so far, produced the highest pumping pressures per applied voltage due to high surface-to-volume ratios. A small pore length across a thin porous substrate enables the development of high electric field strength across each pore, thus increasing the pumping efficiency. However, such single membrane pumps have pressure and flow limitations, such that application of a few volts generate pumping pressure of less than 1 PSI.

[0004] To increase the pumping pressure of low-voltage EOPs, increased surface area for electric double layer formation is required, and hence requires increased thickness of the substrate (for example, membrane). However, there is no current solution for an arrangement of membranes and electrodes in an EOP, such that the high pressure may be accomplished at low running voltages without changing the electric field strength across the individual pores. In addition, standard methods (e.g. hydrolyzing metal electrodes) of generating ionic currents within the EOPs have detrimental effects on the pump operation, due to the release of gas during pumping.

[0005] The low pressure constraint remains a limiting factor for practical utility of low- voltage EOPs. Still, the need for self-containment in analytical, biomedical, pharmaceutical, environmental, and security monitoring applications remains a great challenge, and battery- driven EOPs may serve to replace the limiting control equipment required to run devices, such as high voltage power or pressure supplies.

[0006] In addition to the alternative electrode materials, thin porous ceramic substrates have recently been employed to produce the highest pumping pressure per applied voltage due to high surface-to-volume ratios. The EOP for generating high pressure using low-voltage, external power source and thin EOP substrates, is recently being developed. In general, to increase the pumping pressure of low-voltage EOPs, increased surface area for electric double layer formation is required, however, increasing the thickness of the EOP substrate results in higher running voltages.

[0007] Maintaining high electric field strength, while using low running voltages are two conflicting requirements, which are difficult to accomplish through conventional EOPs. Therefore, the EOPs which are capable of generating high pressure using a lower applied voltage that maintain membrane fabrication requirements are desirable.

[0008] The alternate stacking arrangement of electrodes and membranes for a high pressure EOP solved the challenge of maintaining high electric field strengths using low running voltages. However, the need for self-containment of pumps and actuators in analytical, biomedical, pharmaceutical, environmental, and security monitoring applications has not been met. Therefore, the EOPs which are capable of generating high pressure using a lower applied voltage, without using an external power source, and with minimum membrane fabrication requirements, are desirable.

[0009] To increase the pumping pressure of low-voltage EOPs and thus enable self- contained valve actuation, increased surface area for electric double layer formation is required, and hence increased thickness of the substrate (for example, membrane). However, there is no current solution for an arrangement of membranes and electrodes in an EOP, such that the high pressure may be accomplished at low running voltages without changing the electric field strength across the individual pores. In addition, standard methods (e.g. hydrolyzing metal electrodes) of generating ionic currents within the EOPs have detrimental effects on the pump operation, due to the release of gas during pumping.

[0010] The low pressure constraint remains a limiting factor for practical utility of low- voltage EOPs. Still, the need for self-containment in analytical, biomedical, pharmaceutical, environmental, and security monitoring applications remains a great challenge, and battery- driven EOPs may serve to replace the limiting control equipment required to run devices, such as high voltage power or pressure supplies.

[0011] Maintaining high electric field strength, while using low running voltages are two conflicting requirements, which are difficult to accomplish through conventional EOPs. Therefore, the EOPs which are capable of generating high pressure using a lower applied voltage that maintain membrane fabrication requirements are desirable. Moreover, the simplicity of the EOP processing also makes EOPs a candidate pressure source for actuation of valves within fluidic systems. However, pressure limitations associated with current low- voltage EOPs makes this practically challenging. Still, the ability to package each valve with its own actuator and power source may solve many current problems associated with miniaturization of standard lab-scale control equipment.

BRIEF DESCRIPTION

[0012] Accurately controlled electrode spacing within a thick and dense network of pores may be a solution for maintaining high electric field strength at low running voltages. The EOPs, described herein, comprising a plurality of membranes and electrodes may solve the above mentioned problem and generate a high pressure even at a lower applied voltage using a simple fabrication technique.

[0013] According to a first aspect of the invention, one example of an electroosmotic pump comprises a plurality of membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes, a plurality of electrodes comprising cathodes and anodes, and a power source. Each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternatively and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on the other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane.

[0014] Another example of an electroosmotic pump, comprises a plurality of membranes comprising positive electroosmotic membranes and negative electroosmotic membranes , wherein each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternatively, a plurality of electrodes comprising cathodes and anodes, wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on the other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane, and a power source to provide a voltage between about 0.1 to 25 volts. The membranes and electrodes are operably coupled to the power source to generate a pressure of at least about 0.75 PSI.

[0015] According to a second aspect of the invention, one example of a method of actuating a valve, comprises operatively coupling the valve with an electroosmotic pump; flowing a fluid through the electroosmotic pump; and generating a fluidic pressure of at least 0.75 PSI to actuate the valve, wherein the electroosmotic pump comprises one or more thin, porous, positive electroosmotic membranes and one or more thin porous, negative electroosmotic membranes; a plurality of electrodes comprising cathodes and anodes, and a power source; wherein each of the positive and negative electroosmotic membranes are disposed alternatively and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on the other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive and a negative electroosmotic membrane.

[0016] An embodiment of a microfluidic device, comprises one or more valves; and one or more electroosmotic pumps, wherein the electroosmotic pumps comprise both positive and negative electroosmotic membranes; a plurality of electrodes comprising cathodes and anodes, and a power source; wherein each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternatively and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane; wherein one or more of the valves are operatively coupled to one or more of the electroosmotic pumps.

[0017] The EOPs, as described herein, that comprises a plurality of membranes and pre- charged or chargeable electrodes solve the above mentioned problems by eliminating the need for external power sources to drive EOPs and generating a high pressure even at a lower applied voltage. The use of self-contained high pressure EOPs further reduce the expense and spatial requirements for implementing EOP based fluid control in larger systems and devices. [0018] According to a third aspect of the invention, one example of a pump, comprises a plurality of electroosmotic membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes; and a plurality of electrodes comprising one or more cathodes and one or more anodes; wherein the electrodes are pre-charged, chargeable, rechargeable or combinations thereof and the cathode and anode are operatively coupled to each other, wherein the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternatively, wherein at least one cathode is disposed on one side of one of the membranes and at least one anode is disposed on another side of that membrane, and wherein at least one cathode or anode is disposed between a positive electroosmotic membrane and a negative electroosmotic membrane.

[0019] An example of pump of the invention, comprises a plurality of electroosmotic membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes, wherein each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternatively; a plurality of electrodes comprising one or more cathodes and one or more anodes, wherein the electrodes are pre- charged, chargeable, rechargeable or combinations thereof and the cathode and anode are operatively coupled to each other, wherein at least one cathode is disposed on one side of one of the membranes and at least one anode is disposed on another side of that membrane, wherein at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane, and wherein the electrodes are operatively coupled to generate and store a voltage up to 3 volts to generate a pressure of at least about 0.75 PSI.

[0020] An example of a method of making a pump of the invention, comprises disposing a plurality of membranes, comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes, in an alternative fashion to form a membrane stack, disposing a plurality of electrodes comprising cathodes and anodes, wherein the electrodes are pre-charged, chargeable, rechargeable or combination thereof and wherein at least one of the cathodes is disposed on one side of one of the positive electroosmotic membrane or negative electroosmotic membranes and at least one of the anodes is disposed on another side of that membrane, and at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane, and operatively coupling the electrodes to complete a circuit for activating the electrodes to generate a chemical potential across the membranes. DRAWINGS

[0021] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0022] FIG. 1A is a schematic drawing of an example of an EOP with multiple membranes having the same surface charge and FIG. 1 B is a schematic drawing of an example of an EOP with multiple membranes having alternating (+/-) surface charge;

[0023] FIG. 2 is an example of SEM images showing a bare anodic aluminum oxide (AAO) electroosmotic membrane and a silica treated AAO electroosmotic membrane;

[0024] FIG. 3 is an example of a graph showing increased pressure generated by an embodiment of an EOP with multiple (double) porous substrates of the invention as compared to an embodiment of an EOP with a single porous substrate;

[0025] FIG. 4 is an example of a graph showing a steady flow rate obtained from an EOP assembly of the invention, driven at different voltages;

[0026] FIGs. 5A - 5C are examples of the EOP operation with alternative electrode materials;

[0027] FIG. 6A is an example of a graph showing pumping efficiency of an embodiment of an EOP of the invention using platinum mesh electrodes between nanoporous AAO membranes and FIG. 6B is an example of a graph showing pumping efficiency of an embodiment of an EOP of the invention using Pedot:PSS saturated cellulose paper electrodes between nanoporous AAO membranes;

[0028] FIGs. 7A and 7B are schematic representations of two different embodiments of separate EOP actuations at 0V and at 1 -10 V respectively;

[0029] FIG. 8 is a graph showing the pressure requirement for actuating a version of a microfluidic valve;

[0030] FIGs. 9A and 9B are schematic representations of two different embodiments of inline EOP actuations at 0V and at 1 -10 V respectively;

[0031] FIG. 10 is a graph showing an operating pressure range for valve actuation; [0032] FIG. 1 1 is a schematic representation of an embodiment of a self-contained device comprising EOP;

[0033] FIG. 12 is a graph showing rehydration time of dry buffer or reagents using EOP- based valves;

[0034] FIG. 13 is a schematic drawing of an example of a self-contained unit EOP comprising at least two electroosmotic membranes and three pre-charged electrodes;

[0035] FIG. 14 is a schematic drawing of an example of an EOP with multiple pre-charged electrodes and multiple membranes having alternating (+/-) surface charge, similar to the EOP shown in FIG. 1 B;

[0036] FIG. 15 is an example of a self-contained EOP operation with Pedot:PSS electrodes;

[0037] FIG. 16 is an example of a graph showing two different electroosmotic flow profiles after electrode charging at 10V for 10 min or 30 sec;

[0038] FIG. 17 is an example of a bar graph illustrating flow rates measured from two different self-contained EOPs having different surface area;

[0039] FIG. 18 is an example of a graph showing various phases of self-contained EOP action, including flow rates generated from ionic discharge of the pre-charged electrodes, immediate disruption of the flow upon disconnecting the wire joining the two oppositely charged electrodes, and regaining of the flow rate upon re-connection of the electrodes;

[0040] FIG. 19 is a graph showing increased pumping pressure of an EOP with multiple porous substrates;

[0041] FIG. 20 is a schematic drawing of an example of an assembly of a self-contained unit EOP coupled to a reservoir and a microfluidic channel;

[0042] FIG. 21 is a schematic drawing of an example of a method of membrane actuation for pumping fluid using a self-contained unit EOP; and

[0043] FIG. 22 is a schematic drawing of an example of a method of sequential actuation of membranes for pumping fluid using multiple self-contained unit EOPs.

DETAILED DESCRIPTION

[0044] One or more of the embodiments of the invention relate to an electroosmotic pump (EOP), wherein the EOP generates high pressure using lower applied voltage. High pressure, yet low voltage EOPs may solve the problem of self-contained fluidic systems, where the self- containment refers to the elimination of power, pressure, and input sources external to the device. In addition to fluid movement within the systems, the high pressure EOPs may be operatively coupled to mechanical valves, and used as portable actuation or pressure sources.

[0045] To more clearly and concisely describe the subject matter of the claimed invention, the following definitions are provided for specific terms, which are used in the following description and the appended claims. Throughout the specification, exemplification of specific terms should be considered as non-limiting examples.

[0046] The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as "about" is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Where necessary, ranges have been supplied, and those ranges are inclusive of all sub-ranges there between.

[0047] As used herein, the term "electroosmotic membranes" refers to the membranes which are capable of maintaining electroosmotic flow of a fluid using electroosmosis. Electroosmosis is a motion of a fluid containing charged species relative to a stationary charged medium by an application of an externally applied electric field. Electroosmotic flows are useful in microfluidic systems as the flow enables fluid pumping and control of the flow-rate without using mechanical pumps or valves.

[0048] As used herein, the term "positive electroosmotic membrane" refers to a porous membrane with surface properties, such that induced electroosmotic flow occurs in the direction of the applied electric field in deionized water. It is known to those skilled in the art that the magnitude and direction of electroosmotic flow is dependent on the operating parameters, including the type of running liquid or buffer system used.

[0049] As used herein, the term "negative electroosmotic membrane" refers to a porous membrane with surface properties, such that induced electroosmotic flow occurs in the direction opposing the applied electric field in deionized water. It is known to those skilled in the art that the magnitude and direction of electroosmotic flow is dependent on the operating parameters, including the type of running liquid or buffer system used.

[0050] As used herein, the term "porous material" refers to a material with a plurality of pores, wherein the material is macroporous, microporous, or nanoporous. The porous material may form "porous membrane" and "porous electrodes". The pores can be macropores, micropores or nanopores. In the case of micropores, the average pore size may be, for example, less than about 10 microns, or less than about 5 microns, or less than about one micron. In case of nanopores, the average pore size may be, for example, about 200 nm to about 10 microns, or about 200 nm to about 5 microns, or about 200 nm to about 3 microns. The porous membranes may be made of inorganic materials such as, silicon, alumina, silicon nitride, or silicon dioxide. The porous electrodes may be made of metals such as, platinum (Pt) or gold (Au), or redox materials, such as metal salts or conductive polymers.

[0051] As used herein, the term "interspersed" or "intervening" refers to a position of a membrane or an electrode which is present between two other electrodes or two other membranes respectively. For example, a membrane is interspersed means the membrane is disposed between two different electrodes, wherein the electrodes are oppositely charged. In another example, an electrode is intervened or interspersed means the electrode is disposed between two membranes with opposite surface charge. The term "disposed between" is alternatively used herein as "interspersed" or "intervened".

[0052] As used herein, the term "operatively coupled" refers to a functional interaction between one or more components. For example, one or more valves may be operatively coupled to an EOP, and actuation of the valve may be controlled by controlling the EOP by changing the number of membranes, electrode materials, membrane materials or applied voltage. Multiple functions of the valve may be controlled by the EOP control unit, and may be included within the definition of operatively coupled.

[0053] As used herein, the term "battery-free EOP" refers to an EOP with no external power source or battery. The EOP has an integrated power source in the electrodes of the EOP, which drives the EOP function and generates high pressure. In one embodiment, the "battery- free EOP" has pre-charged or chargeable or re-chargeable electrodes which are able to store chemical charges for some time and supply the power for the EOP operation.

[0054] As used herein, the term "pre-charged" refers to an electrode which is induced with charges and able to store that charge for EOP operation and are ready to be used for the pumping operation. In some embodiments, the EOP comprises pre-charged electrodes during assembly or packaging of the EOP, so that the EOP is ready to use without charging the electrodes.

[0055] As used herein, the term "chargeable electrode" refers to an electrode which is charged up before operating the EOP. The chargeable electrodes are devoid of pre-induced charges during assembly or packaging of the EOP and induced with charges at any point of time before operating the EOP. As used herein, the term "re-chargeable electrode" refers to an electrode which has the ability to be induced with charges repeatedly and drives the electrode operation for pumping fluids. The chargeable or re-chargeable electrodes may also be packaged with the EOP.

[0056] Various embodiments of the pumps comprise a plurality of electroosmotic membranes and a plurality of electrodes comprising cathodes and anodes, wherein the electrodes are pre-charged, chargeable, rechargeable or combinations thereof. The oppositely charged electrodes, such as cathodes and anodes are operatively coupled to each other. The electroosmotic membranes comprise one or more positive electroosmotic membranes and one or more negative electroosmotic membranes, which are disposed alternatively. At least one cathode is disposed on one side of one of the membranes and at least one anode is disposed on another side of that membrane, and wherein at least one cathode or anode is disposed between a positive electroosmotic membrane and a negative electroosmotic membrane. In one or more embodiments, the pumps are EOPs. The EOP drives fluid flow independent of an external power supply.

[0057] As used herein, the term "transverse direction" refers to the movement of fluid across an EOP structure in a direction that is parallel to the electric field. In an EOP structure, the movement of fluid is from one side of the membrane to the other.

[0058] Embodiments of the EOPs comprise a plurality of electroosmotic membranes, a plurality of electrodes comprising cathodes and anodes, and a power source. The electroosmotic membranes comprise one or more positive electroosmotic membranes and one or more negative electroosmotic membranes. Each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternatively. In one embodiment, at least one of the cathodes is disposed on one side of one of the electroosmotic membranes and at least one of the anodes is disposed on the directionally opposite side of the electroosmotic membrane, and at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and a negative electroosmotic membrane.

[0059] One or more examples of a method of actuating a valve comprises operatively coupling of the valve with an EOP, flowing a fluid through the EOP, and generating a fluidic pressure of at least 0.75 PSI to actuate the valve. In this example of the method, the EOP comprises one or more thin, porous, positive electroosmotic membranes and one or more thin porous, negative electroosmotic membranes; a plurality of electrodes comprising cathodes and anodes, and a power source.

[0060] The EOP is fabricated with multiple porous electroosmotic membranes and electrodes in a layer-by-layer structure, wherein alternatively charged membranes are stacked or fabricated one after another. The electrodes are disposed on both sides of each of the membranes forming intervening layers between the stacked membranes. For example, Pt is sputtered on the surface of the porous membrane, wherein the porous membrane is anodic aluminum oxide or AAO.

[0061] In one embodiment, a simplified structure of EOP, which is alternatively referred to herein as "unit structure of EOP" or "unit of EOP", comprises at least two electroosmotic membranes and at least three electrodes along with a power source, wherein the electroosmotic membranes comprise one positive electroosmotic membrane and one negative electroosmotic membrane and the electrodes comprise at least two cathodes and one anode or at least two anodes and one cathode.

[0062] Each of the electroosmotic membranes has a cathode and an anode associated with it, and each EOP unit within the stack is electrically isolated from the next. This enables dense stacking of the nanoporous electroosmotic membranes, without changing the electric field strength across individual pores. For example, each of the anodes is disposed on one side of the electroosmotic membrane and each of the cathodes is disposed on the other side of the membrane, thus every other electrode is attached to the same terminal on the battery/power source.

[0063] In one exemplary embodiment, a cathode is disposed on a negative electroosmotic membrane and an anode is disposed on the other side of the negative electroosmotic membrane, which results in the negative electroosmotic membrane to intersperse between the cathode and anode. In another exemplary embodiment, an anode is disposed on (upstream of) a positive electroosmotic membrane and a cathode is disposed on other side (downstream) of the positive electroosmotic membrane, such that the positive electroosmotic membrane is interspersed between the anode and cathode.

[0064] Various arrangements or rearrangements of the membranes and electrodes are possible, while maintaining alternatively charged membranes stacked with two oppositely charged electrodes on both sides of each of the membranes and keeping one electrode common between each of the two membranes. In one embodiment, in each of the EOPs, only one of the cathodes or anodes is disposed between two oppositely charged electroosmotic membranes, such as, in one exemplary configuration, the unit structure of EOP has one anode which is common between a positive electroosmotic membrane and negative electroosmotic membrane, and that results in a sequential disposition of a cathode, a positive electroosmotic membrane, an anode, a negative electroosmotic membrane, and then again another cathode. In another exemplary configuration, the unit EOP structure has one cathode which is common between the positive electroosmotic membrane and negative electroosmotic membrane, which results in a sequential disposition of an anode, a positive electroosmotic membrane, a cathode, a negative electroosmotic membrane, and then again, another anode.

[0065] In some exemplary embodiments, multiple units of EOPs are stacked together, wherein the multiple electroosmotic membranes and electrodes are arranged in a layer-by- layer structure. Each of these layers remains electrically insulated due to the alternating anode/cathode arrangement, without physical insulation of the electrode material itself. In one example, a first unit of an EOP is followed by a second unit of an EOP, wherein the second unit of the EOP comprises a negative electroosmotic membrane that is disposed either upstream or downstream of the positive electroosmotic membrane of the first unit of the EOP. For example, in one embodiment, the negative electroosmotic membrane of the second unit of the EOP is disposed downstream of an anode of the first unit of the EOP, and a cathode is disposed on the directionally opposite side of the negative electroosmotic membrane, such that the membrane is interspersed between the anode and cathode. The interspersed negative electroosmotic membrane is further followed by a positive electroosmotic membrane, which is disposed downstream of the cathode, and an anode is further disposed on the directionally opposite side of the positive electroosmotic membrane to form the second unit of the EOP that is situated downstream of the first unit of the EOP. In some other embodiments, a third unit of an EOP is further formed downstream of the second unit of the EOP, a fourth unit of an EOP is further formed downstream of the third unit of the EOP, and so on. Hence, by stacking the multiple units of the EOPs, a single "integrated EOP" is generated, wherein the integrated EOP comprises multiple membranes and electrodes and the electrodes are present as intervening layers between each of the membranes. The multiple units of the EOPs provide increasing pump surface area to the single integrated EOP, which generates higher pumping pressure without using complicated fabrication or higher input voltage. The stacking architecture thus enables high pressure pumping at low voltages, resembling a single unit of an EOP.

[0066] Multiple low-voltage, high pressure EOPs may be used together in a series or in parallel. The EOPs may also be integrated within micro-meter and millimeter scale fluidic systems, by, for example, stacking them together to increase the pressure output or to maintain flow rate to overcome the viscous losses and pressure loads in long channels. The devices described herein may be run on small batteries, and can thus enable a variety of hand held devices. The high pressure EOPs may also be operatively coupled to mechanical control structures, such as valves, and provide pressure output or the forces necessary for actuation in a self-contained manner.

[0067] An alternative attempt for a method of stacking multiple units of the EOP's to increase a pumping pressure in portable fluidic systems is illustrated in FIG. 1A, wherein each of the membranes is an AAO with Pt sputtered on both of the surfaces. As illustrated in FIG. 1A, multiple membrane stacking arrangement 10 shows each of the membranes 12 is with the same surface charge, for example, either alumina membrane or silica membrane. Each of the membranes 12 is interspersed between two oppositely charged electrodes, such as cathode 20 and anode 22. Each of the membranes is a porous membrane and the electrodes are also porous electrodes, which form channels 14 through the membrane stack. In this configuration, stacking multiple low-voltage units of the EOPs of similar zeta potential results in an electric field interference 18 and bidirectional electroosmotic flow 16, as each of the AAO needs to be electrically insulated with fluidic continuity with the next EOP.

[0068] This complication is eliminated by developing an arrangement of a low-voltage high- pressure EOP 24 of FIG. 1 B. The EOP of this embodiment as illustrated in FIG. 1 B, utilizes alternating nanoporous membranes 12 and 26 with opposing zeta potentials. Each of the membranes is interspersed between two oppositely charged electrodes, such as cathode 20 and anode 22. For membrane stacked EOP, the intervening electrode layers are common, such as for first and second membranes 12 and 26, the intervening electrode is 22, for second and third membranes 26 and 12, the intervening electrode is 20, for third and fourth membranes 12 and 26, the intervening electrode is 22, and so on. The porous membranes and electrodes form channels, such as 28, wherein unidirectional electroosmotic flow is 30. The stacking pattern of the alternating membranes and intervening electrodes enables generation of a unidirectional flow 30 within the applied electric field 32.

[0069] An electrical double layer is formed in each alternating layer of the EOP and moves in the same direction through the membrane stack due to the alternating positive and negative electroosmotic membrane. Depending on the ionic concentration, the thickness of the electric double layer, which is referred to as the Debye length, varies from 3 nm to 300 nm for deionized water. The Debye length may become comparable to the nanopores within the EOP, depending on the electroosmotic membrane used. Furthermore, the use of thin membranes and corresponding interspersed electrodes enables the application of high electric field strengths across each of the alternating electroosmotic membranes. In order to increase pumping pressure, a larger surface area is required for double layer formation, without affecting field strength across the pores. In the EOP stack, the oppositely charged Debye layers move through the successive electric fields, and the net movement results in relatively higher electroosmotic pressure development due to the dense arrangement of the pores.

[0070] Polarity of the surface and zeta potential dictates the electroosmotic flow direction. The basic flow principle of EOPs is based on the surface charge of the membranes and the formation of electrical double layers. For example, when an aqueous solution contacts a glass surface (or silica), the glass surface becomes negative due to the deprotonation of surface silanol groups. An electrical double layer forms at the surface as a result of the deprotonation. The surface charge attracts dissolved counter-ions and repels co-ions, resulting in a charge- separation and forming an electrical double layer. The mobile ions in the diffused counter-ion layer are driven by an externally applied electrical field. The moving ions drag along the bulk liquid through the membranes and develop the electroosmotic flow. The EOP stack enables formation of a large surface area for electric double layer, without increasing the overall diameter of the pores or the electric field strength across each individual pore. Thus, higher pumping pressure is obtained without necessitating high driving voltage.

[0071] The electroosmotic flow of the fluid builds up an electroosmotic pressure in the EOP using applied voltage. Unlike conventional pumps, one or more embodiments of the EOP generate high pressure at comparatively lower applied voltages. In accordance with one embodiment, the EOP is configured to operate by applying less than 25 volts across each of the membranes to achieve electric fields greater than 100 V/meter across each of the electroosmotic membranes within the pump. In one example, the EOP is operated at less than or equal to 10 volts. In some other examples, the EOP is configured to operate at less than or equal to 5 volts.

[0072] The pumping pressure may be tuned or modified based on the requirement of various applications. In some embodiments, the EOP (unit structure EOP or integrated EOP) is configured to generate a pressure of at least about 0.5 PSI. Current single membrane or single element EOPs provide pumping pressure between 0.1 and 0.75 PSI. In one or more embodiments, using different membranes, such as AAO membrane, the pressure generated is at least about 075 PSI. In some embodiments, by increasing the number of electroosmotic membranes in an EOP (or integrated EOP), the output pressure may be increased proportionally. In one exemplary embodiment, the EOP is configured in a series stack to generate a pressure of at least about 10 PSI. In some other embodiments, the pressure is increased up to 100 PSI, by increasing the number of stacked units of EOPs in an integrated EOP system.

[0073] The electroosmotic membranes are porous, more specifically the membranes are nanoporous. The diameter of the pores is about 10 nm to 500 nm. While stacking the membranes one after another, the pores of various membranes may be aligned in a straight line to form a continuous straight vertical channel starting from the top layer to the bottom layer (membrane), allowing a fluid to pass through the channels. In some embodiments, the pores of the various membranes may not be aligned in a straight line through the stacked membranes to form a straight channel. In these embodiments, although the pores are not aligned in a straight line, the fluid can still pass through the non-linear channels formed across multiple membranes. [0074] Flow direction for positive electroosmotic membranes is different than that of the negative electroosmotic membranes. When the surface charge of the membrane is positive, the fluid flow proceeds in the direction of the electric field, and when the surface charge is negative, the fluid flow proceeds in the direction opposite to the electric field. The membranes may be stacked without individual electrical insulation. Therefore, the membranes are merged, with a common electrode in between two membranes, and the fabrication technique resolves the problem of individual electrical insulation, and increases the pressure using multiple membranes. The additive pressure in series results from the membrane stacking.

[0075] The selection of electroosmotic membranes is typically restricted to a thin membrane, as the thin-nanoporous membrane structure increases the electric field strength at a given applied voltage. Each of the membranes has a thickness of about 10 nm to 10 mm. In one exemplary embodiment, 60 μηη thick bare or silica-coated AAO membranes are used in the EOP stack, wherein the interspersed electrodes are Pt directly sputtered on the membrane surfaces. In another exemplary embodiment, the interspersed electrodes are comprised of a thicker, porous paper substrate coated with a conductive polymer.

[0076] The composition of the electroosmotic membranes may vary. In some embodiments, the electroosmotic membranes comprise one or more dielectric materials or polymers with grafted ionizable functionalities to achieve zeta potential similar to the dielectrics, and combinations thereof. The dielectric materials may comprise but are not limited to tungsten oxide, vanadium oxide, silicon dioxide or silica, common glasses such as silicates, silicon carbide, tantalum oxide, zirconium oxide, hafnium oxide, tin oxide, manganese oxide, titanium oxide, silicon nitride, chromium oxide, aluminum oxide or alumina, zinc oxide, nickel oxide, magnesium oxide and combinations thereof.

[0077] In some embodiments, the electroosmotic membrane may be an insulator. In some embodiments, the electroosmotic membrane may comprise an oxide, metal oxide or a metal nitride. Any of the oxides, metal oxides or nitrides may be used in the membrane, and may comprise but are not limited to hafnium oxide, zirconium oxide, alumina_, or silica, as the insulators. The electroosmotic membranes may comprise polymers, selected from PDMS, COC, PMMA, PC, or other materials with graftable surface chemistries.

[0078] Depending on the surface electric charge, the electroosmotic membranes may be divided in two types, positive electroosmotic membranes and negative electroosmotic membranes. The positive electroosmotic membrane may comprise a material with a surface charge similar to silica in Dl water and the negative electroosmotic membrane may comprise a material with a surface charge similar to alumina in Dl water, and at a neutral pH. In some embodiments, the AAO membrane is coated using a sol-gel material deposition, chemical vapor deposition (CVD) atomic layer deposition (ALD), or molecular vapor deposition (MLD). The fabrication techniques are used to produce the AAO membrane with an expected surface charge. For example, a bare AAO membrane contains a positive surface charge in water. In another example, the bare AAO membrane (FIG. 2A), is treated with silica to form the silica coated membrane (FIG. 2B) that contains the negative surface charge in water. The SEM images of the bare AAO membrane and the silica coated AAO are shown in FIG. 2A and FIG. 2B. By selecting an appropriate surface coating material such as silica, the flow rate of the fluid passing through the membrane may be increased.

[0079] In one embodiment, the electroosmotic membranes used in the EOPs are hydrophilic in nature, which enables the membrane to wet out quickly and completely. Hence, the hydrophilic membranes eliminate the need for expensive pre-wetting treatment and increase the flow rate of the fluid passing through the membranes of the EOPs.

[0080] In one or more embodiments, the EOPs described herein, control the surface zeta potential of the membrane by embedding internal electrodes. For example, by embedding thin Pt electrode layers in the insulating membrane stack, the zeta potential of the surface of the membrane may be actively controlled. The zeta potential of the membrane may vary as a function of buffer, ionic strength and pH, and the surface characteristics. In one embodiment, the electroosmotic membrane has a zeta potential in a range of -100 mV to +100 mV. The magnitude of zeta potential for aluminum oxide in contact with 1 mM KCI, at pH=7 is 37 mV. The zeta potential for silica, zinc oxide, and zirconia is |f|=80 mV; 45 mV and 90 mV, respectively.

[0081] By increasing the number of membranes, the EOPs are able to increase the operating pumping pressure. As noted, the basic unit structure of the EOP comprises at least 2 membranes, wherein the surface charges are opposite for two membranes at the time of the fluid flow through the membranes under the influence of the electric field. In some embodiments, the EOP comprises about 2 to 100 membranes in series. The total output pressure increases proportionally to the number of membranes within the stack, and the pump is designed based on the application specific fluidic load. Hence, the efficiency of the EOPs may be changed, such as increasing or decreasing the pressure, according to the user's need. For example, the stall pressure of an EOP comprising a double stack of an AAO and a silica coated AAO is higher compared to an EOP with single AAO, as shown in FIG. 3. The result shows a 2X increase in pumping pressure with the double stack membrane. The flow rates, measured by a commercial micro-electromechanical systems (MEMS) flow sensor, decreases with increasing applied back pressure to the pump and the stall pressure is identified at the zero flow position. In one or more examples, at least two membranes are required to construct a single unit of EOP and this one unit of EOP generates pressure of about 2 PSI. In another example, an EOP constructed with 20 membranes generates pressure of about 40 PSI.

[0082] As noted, the EOP comprises a plurality of electrodes, wherein the electrodes are disposed on the electroosmotic membranes. The electrodes employed by the EOP are macroporous, which allow transverse fluid flow. In some embodiments, the diameter of the macropores present on the electrodes may be in a range of 50 nm to 10 mm. In one embodiment, the diameter of the macropores is 1 mm.

[0083] In one or more embodiments, the use of redox polymer electrodes increases the flow rate at the same applied voltage compared to some of the conventional metal coated electrodes. The increase of flow rate is due to the elimination of the over-potential, which is required to drive the pumps comprising metal coated electrodes using hydrolysis. For example, operation of integrated EOP assembly with paper or cellulose electrodes enable the EOP to generate a stable flow rate of 10's μΙ_/η"ΐίη at voltages below 5 V, as shown in FIG. 4.

[0084] The material composition of the electrodes may vary. In some examples, the electrodes comprise a macroporous metal, redox metal salt, metal oxide, metal nitride, conductive polymer, redox polymer and combinations thereof. In some embodiments, the electrodes comprise a metal. The examples of materials used for electrodes include, but are not limited to, noble metals such as Au, Ag, Ru, Rh, Pt or Hg, redox metal salts such as Ag/AgCI or Ag/Agl, and metal oxide such as Ta₂0₅, Ru0₂ or AgO.

[0085] In some embodiments, structural supports for the electrodes are made of conductive polymers, may be selected from polyacetylenes, polyphenylene vinylenes, polypyrroles, polythiophenes, polyanilines, polyphenylene sulfide or polyfluorenes. In some embodiments, the electrodes are made of a base material, such as a macroporous polymer, coated with a conductive material. In one embodiment, the electrodes are coated with redox polymer, redox metal salts or metal oxides. In some embodiments, the electrodes are coated with redox polymers, which include but are not limited to PEDOT, PEDOT:PSS, Poly(1 ,5- diaminoanthraquinone), poly(2-2-dithiodianiline) or pDTDA. In some examples, the electrodes comprise a porous deposition of an inert metal or a thick mesh of an inert metal, such as Pt. The electrode may further comprise a coating made by a thin deposition of a metal on a thick porous substrate. The electrode may be coated with a conductive or redox polymer on a thick porous substrate. In some other embodiments, the electrode may comprise a thin electroplating of a metal salt or oxide and combinations thereof.

[0086] In some embodiments, the electrodes are made of macroporous polymers. In some embodiments, the macroporous polymers such as glass or rubbery polymers, which maintain porosity in a dry state or when immersed in a solvent, may be used as electrodes. The macroporous polymer may include, but are not limited to, natural papers such as cellulose; synthetic paper such as polypropylenes or polyethylene, synthetic sponges such as polyethers, PVA, or polyesters; or polymer mesh material such as Polyurethane, PTFE, nylon, or polyethylene. In one embodiment, cellulose is used as electrodes, by soaking a paper in a conductive polymer.

[0087] In one or more embodiments, the polymeric material used, as structural support for the electrodes, or as coating for the electrodes is selected from poly(olefins), halogenated poly(olefins), poly(cylco olefins), halogenated poly(cylco olefins), poly(styrenes), halogenated poly(styrenes), poly(propylenes), poly(ethylenes), halogenated poly(ethylenes), poly(tetrafluoroethylenes), poly(sulfones), poly(ether sulfones), poly(arylsulfones), poly(phenylene ether sulfones), poly(imides), poly(etherimides), poly(vinylidene fluorides), poly(esters), halogenated poly(esters), poly(ethylene terephthalates), poly(butylene terephthalates), poly(carbonates), polyvinyl halides), poly(acrylics), poly(acrylates), halogenated poly(acrylates), poly(methacrylics), poly(methacrylates), poly(anhydrides), poly(acrylonitriles), poly(ethers), poly(arylene ether ketones), poly(phenylene sulfides), poly(arylene oxides), poly(siloxanes), cellulose acetates, cellulose nitrates, poly(amides), nylon, ceramics and combinations thereof.

[0088] In one or more examples, the nanoporous membranes, such as, Al₂0₃ or silicon membrane may be coated with a thin conducting layer of metal, such as Pt, or a conducting material. In some other examples, the electrode material is sputtered on the membranes, for example Au, Pt or any other noble metal may be sputtered on the porous Al₂0₃ or silicon membrane surface to form anode and cathode and generate an external electric field.

[0089] A nanoporous EOP assembly may be disposed in a channel to form an electroosmotic flow setup. The channel may be a microfluidic channel. In some examples, gas bubbles are released on the Pt electrode surface and impede flow through the EOP. However, in one embodiment of the multiple membrane-based EOP, stable flow rates of the fluid may be achieved within seconds, even when pumping into channels or structures with high hydraulic resistance. This is due to the high pumping pressure of the stacked EOPs and the fact that, the redox electrodes reduce bubble formation within the pump and therefore allow use of the EOPs in microchannels without interruption.

[0090] In one example, the AAO is selected as the membrane and cellulose is selected as the electrode, wherein the cellulose (or paper) electrodes are coated with a conductive liquid polymer. Hence, the EOP allows the AAO membrane stacking by disposing multiple pieces of paper (cellulose) wetted with a conducting polymer solution as electrodes in between each of the AAO membranes. As noted, the EOP is configured to generate a transverse fluid flow through the AAO and paper stack.

[0091] In one embodiment, the EOP is packaged with a power source, wherein the entire pump assembly may be self-contained. The low voltage operation described herein requires minimal current draw within each of the serially connected membranes of the EOPs. Hence, the multiple membrane-based EOPs generate higher pressures without the requirement of a large power supply.

[0092] In one or more embodiments, a power source is used to provide a voltage between about 0.1 to 25 volts, wherein the membranes and electrodes are operably coupled to the power source to generate a pressure of at least about 0.75 PSI. In some other embodiments, a power source may be used to provide a voltage between about 0.1 to 10 volts, wherein the membranes and electrodes are operably coupled to the power source to generate a pressure of at least about 0.75 PSI

[0093] To provide a sustained current without interrupting a fluid flow in an EOP remains a challenge so far, which is addressed herein by using various electrodes including metal oxide or polymeric electrodes. A voltage applied to the electrode within the EOP stack results in a passage of an ionic current through the electroosmotic membranes. For example, a voltage applied to the standard Pt electrode results in a hydrolysis followed by generating gas to the electrodes, as shown in FIG. 5A. In EOPs, the hydrolyzed ions are formed at the surface of the metal electrodes, thus releasing hydrogen and oxygen gas at opposite ends of the nanopores (FIG. 5A).

[0094] Though gas accumulation may be minimal at the low driving voltages, bubble formation remains a problem in the dense nanoporous stacks. A voltage applied to a metal oxide electrode, such as silver oxide electrode results in redox reaction as shown in FIG. 5B. Similarly, a voltage applied to the conductive or redox polymer electrode, such as PEDOT/PSS electrode also results in a redox reaction as shown in FIG. 5C. In either case, the current passes across the membranes of the EOP due to the generation of ions by the reactions at the electrodes and the current exists until reactive sites in the electrodes are exhausted.

[0095] An example operation of EOP assembly using Pt mesh electrodes between nanoporous AAO membranes is shown in FIG. 6A. The platinum mesh electrode is made from a wire with 0.06 inch diameter, and the AAO membranes have 20 nm pore size. The graph of FIG. 6A reflects an increased flow rate with increasing applied voltage, though the flow rate in this example plateaus and then decreases after a certain applied voltage, such as 40 V. The EOP may be used in a larger fluidic system as the pressure source, wherein the overall flow rate in the total system may depend on the hydraulic resistance of that system, and the pressure output of the pump. In one embodiment, the pressure output is determined by the number of membranes present within the EOP stack.

[0096] An example operation of EOP assembly using Pedot:PSS saturated cellulose paper electrodes between nanoporous AAO membranes is shown in FIG. 6B. The paper electrode has 0.5 mm paper thickness, and the AAO membranes are with 20 nm pore size. The graph of FIG. 6B reflects the increased pumping efficiency with increased applied voltage. The increased pumping efficiency is due to uniformity of the electric field, when compared to the Pt mesh electrode (with diameter of 0.06 inch), and elimination of the over-potential required when using Pt electrodes. Utilization of the redox polymer eliminates the challenge of gas production at metal electrodes, and enables uninterrupted EOP operation.

[0097] In one or more embodiments, the high pressure EOP may comprise a control circuit to maintain a constant current or voltage, and therefore maintains a constant fluid flow or pressure output during an operation. In one embodiment, the EOP comprises a controller to maintain a constant fluid flow. In one example, the controller comprises a micro controller circuit.

[0098] In some embodiments, a conductive paste, resin, or glue is deposited onto the electrode to create a common electrical connection to the membranes within the membrane stack. In other embodiments, metal coatings or foils are used to make an external electrical connection to the membranes within the stack. In one example, a silver paste is deposited on each of the electrodes to take a common connection output from the membrane stack.

[0099] One or more examples of the method for depositing electrodes and patterning the electroosmotic pumps comprise contact printing, photolithography or wire bonding techniques. The area of external metal cathode and anode may be coated by photolithographic patterning. An E-beam evaporation or alternative sputter process may be applied for initially disposing or depositing metal (e.g. Au, Pt, or any noble metal) electrodes as anodes or cathodes on both sides of the membrane (e.g., porous anodic aluminum oxide or macroporous silicon). The metal cathode or anode may be adapted to cover the surface of the AAO membrane without obstructing the openings of the nanopores.

[00100] In the EOPs, the fluid may be electroosmotically pumped through one or more membranes transversely. In one embodiment, the fluid is electroosmotically pumped between two membranes that are stacked one upon another, wherein the membranes are either directly in contact or spaced with a small distance of 1 mm or less. Larger distances within the EOP stack may decrease electric field strengths across the electroosmotic membranes, and therefore flow rates within the pump. Therefore, a pump may sustain high back pressure (e.g., >1 atm) and still maintain adequate fluid flow when a gap between two of the membranes is small, for an example, 500 μηη. The EOP of this embodiment increases the pumping pressure associated with low voltage (battery) EOPs, enabling use in field-able, self-contained, and battery-operated systems.

[00101] In some embodiments, the membranes are further operatively connected to at least two reservoirs comprising fluids. In one embodiment, the pumping liquid or fluid or working solution, which is used in the EOP has a pH from about 3.5 to 8.5. In an alternative embodiment, the pumping solution is a borate buffer with a pH of about 7.4 to 9.2 and an ionic strength between about 25 to about 250 mM.

[00102] The core structure for the membrane and electrodes may be adapted to function with other pump components such as, for example, fluid chambers, inlet port(s), and outlet port (s). These applications for EOPs include, but are not limited to, lab-on-a-chip devices and applications, inkjet printing, ink delivery, drug delivery, liquid drug delivery, chemical analysis, chemical synthesis, proteomics, healthcare related applications, defense and public safety applications; medical applications, pharmaceutical or biotech research applications, environmental monitoring, in vitro diagnostic and point-of-care applications, or medical devices. In one embodiment, the EOPs may also be incorporated into MEMS devices. Other applications include, but are not limited to, PCR (DNA amplification, including real time PCR on a chip), electronic cooling (e.g., for microelectronics), pumping ionized fluids and colloidal particles, or adaptive microfluidic mirror arrays.

[00103] Moreover, high pressure EOPs may be coupled to one or more mechanical valves and switches, and used as an actuating pressure source, in contrast to a conventional mechanical actuator. Furthermore, implementation of such self-contained fluid control systems from a limited number of materials using simple fabrication techniques enable application of the portable pump and control elements within the disposable cartridges. Some more examples include, electroosmotic valves using the EOPs by opposing pressure driven flow, use of the EOPs to fill and empty flexible reservoirs to induce functionality via shape change and electroosmotic-actuators. A benefit for at least one of the embodiments is high throughput screening and compound profiling.

[00104] For developing electroosmotic actuators or electroosmotic valves, the battery- operated EOP is desirable. Pumping of complex buffers and reagents, typically associated with bio-analysis, may be achieved using one or more EOPs associated with one or more valves present in a number of parallel, valved-chambers Each of the chambers may contain different types of buffers or reagents which are different from the running buffer. The running buffer may be used either for moving fluid or reconstituting dried materials from each of the chambers. Pressure and flow rates generated from the EOPs may be controlled to mix the fluids collected from different chambers, wherein the EOP actuation may be utilized to create a self-contained system. In some embodiments, the self- contained system may be used for controlling the concentration of each of the fluids to be mixed or to flow in various channels/chambers. In this case, the flow rate and duration of each EOP-based valve actuation may control the amount of fluid that enters to or exits from each storage chamber.

[00105] Typically, EOP experiments are conducted with Dl water or buffers and the addition of some pH buffering compounds, or even simple salt solutions decreases the flow rate and pressure output. However, the pumping pressure of EOPs may be increased by varying the number of membranes in the EOP stack. Various types of valves may be used in different devices for actuating and controlling the fluid flow, and therefore to control or maintain the fluid concentrations. Non limiting examples of the valves may include a ball valve, butterfly valve, check valve, choke valve, pinch valve and gate valve. Each of the valves may have different designs.

[00106] As noted, the examples of a method of actuating a valve comprises operatively coupling of the valve with an EOP, flowing a fluid through the EOP, and generating a fluidic pressure of at least 0.75 PSI to actuate the valve. In this example of the method, the EOP comprises one or more thin, porous, positive electroosmotic membranes and one or more thin porous, negative electroosmotic membranes; a plurality of electrodes comprising cathodes and anodes, and a power source; wherein each of the positive and negative electroosmotic membranes are disposed alternatively and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive and a negative electroosmotic membrane.

[00107] In one example of the method, the required fluidic pressure is of about 0-30 PSI to actuate the valve, or in some embodiments the required fluidic pressure is of about 30-75 PSI to actuate the valve. The fluidic pressure is generated by operating the EOP by applying less than 25 volts across each of the membranes. The application of less than 25 volts across each of the membranes achieves electric fields greater than 100 V/m across each electroosmotic membrane within the pump.

[00108] In some examples of methods, the fluid flows through the electroosmotic pump in a transverse direction with a flow rate of about 0.1 μΙ_Ληίη to 10 mL/min per cm2 of surface area across the membranes.

[00109] In one or more examples of the methods, the EOP is further operatively coupled to at least one reservoir comprising a fluid, may be referred to herein, as pumping fluid which passes through the EOP and then actuates the valve. In another example of the method, the fluid flow is controlled to maintain a constant fluidic pressure using a voltage or current controller. A mechanical or control circuit may also be used to selectively or successively apply voltage between a number of EOPs, and therefore control actuation among a number of valve or storage chambers.

[00110] FIGs. 7A and 7B illustrate the mechanism of actuation of a valve placed in a microfluidic channel. In one exemplary embodiment, FIG. 7A shows an example schematic of an EOP operably coupled to an elastomeric pinch-valve, such as the microfluidic valves utilized in GE's Biacore™ SPR system. In one illustrative example 40 (as shown in FIG. 7A), a reservoir 42 contains a fluid having a fluidic pressure P1 , wherein the fluid is subjected to flow through the EOP 44 and then through the microfluidic channel 46. The EOP 44 is situated between the reservoir and the valve, and the fluid present in the chamber 38 of the EOP has a fluidic pressure of P2. The valve 48 is placed in an interface of the EOP 44 and the channel 46. The EOP pump 44, as shown in the center, allows liquid from a small reservoir 42 into a small chamber 38 directly above the valve 48, increasing the pressure above the valve and forcing the elastomeric component 48 into the channel below 45/47. The fluid enters to the microfluidic channel through the inlet 45, passes through the channel and exits through the outlet 47. The EOP 44 is not able to generate any pressure difference, as the pressures P1 and P2 are same at 0 V and unable to actuate the valve 48 as well, which results in fluid flow through the channel 46 without any hindrance.

[00111] FIG. 7B shows, the elastomeric component 48 may be used to valve off the channel, if the stall pressure of the pump (the back pressure at which the EOP stops moving liquid from one chamber to the next) is larger than the actuation pressure of valve. In another illustrative example 52 (as shown in FIG. 7B), a reservoir 42 contains a fluid having a fluidic pressure P1 . The fluid is subjected to flow through the EOP 44 followed by passing through the microfluidic channel 46. The fluid present in the chamber 50 on the opposite side of the EOP has a fluidic pressure P2. The valve 48 is placed in an interface of the EOP 44 and the channel 46. In this example, using the applied voltage between 1 to 25V, the fluid flows through the EOP 44 and that causes increasing the pressure P2 in the chamber 50 of the EOP. Once P2 exceeds the valve closing pressure, the valve opens to the channel results in blocking of the channel. Therefore the pressure difference, herein, results in an actuation of the valve 48, which blocks the fluid flow through the channel 46. This concept may be expanded to include multiple EOP- operated valves in series or in parallel.

[00112] As an example, FIG. 8 shows the pressure requirement for actuating a version of the elastomeric microfluidic valve contained within GE's Biacore™ (SPR technology) system. A flow rate is measured with the valve in an open configuration, by applying a pressure. As the valve closes and fluidic resistance increases, the flow rate of the fluid passing through the channel decreases, and becomes zero at the pressure of 4 PSI, as shown in FIG. 8. The valve shows full closure at 4 PSI, showing that the further actuation is possible only while using pressure of at least more than 4 PSI using valves (as shown in FIG. 7A and B) combined with the high pressure EOPs, unlike the valves combined with standard low pressure EOPs. In this example, the valve actuation fluid is separated from the fluid in channel by the elastomeric valve.

[00113] In some embodiments, the method of actuation of the valve enables mixing of multiple buffers or reagent components, wherein the buffer or reagent components are placed in a serial, parallel, or combination of serial and parallel positions with the EOPs.

[00114] In an exemplary embodiment, a self-contained fluidic valve is used in a fluid path, wherein for example, the valve is a check valve. Two check valves regulate the flow of two different fluids through a single channel by actuating the valves depending on the required fluid flow, as illustrated in FIGs. 9A and 9B. Depending on the requirement of one particular fluid flow, such as fluid 1 , the appropriate valve may actuate while applying voltage to the corresponding EOP.

[00115] FIGs. 9A and 9B show a schematic example of two in-line check valves operatively coupled to high pressure EOPs. Two fluid reservoirs 58 and 56 are connected to a single outlet 70 through 2 separate EOPs 60 and 62. The choice of fluid flowing through the single outlet is made by applying a voltage, and initiating a flow through one of the two EOPs. The EOP actuates the in-line check valve 72 or 74, and allow fluid movement from one of the reservoirs to the outlet. At the same time, the opposite check valve is forced shut, isolating the fluid flow from the second reservoir. Initiation of the flow in the other EOP causes actuation of the opposite check valve, and flow from the other reservoir.

[00116] As illustrated in FIG. 9A, an exemplary embodiment of a system 54, wherein two reservoirs are 56 and 58. The reservoirs 56 and 58 hold fluid 1 and fluid 2 with fluidic pressure P3 and P4 respectively. The reservoir 56 is connected with an EOP 60, and the check valve 64 is placed downstream of the EOP 60. In the EOP 60, the fluidic pressure is P5. The microfluidic channel is connected to both of the chambers 56 and 58 and has an outlet 70. The reservoir 58, which contains fluid 2, is connected to the EOP 62, and the check valve 66 is placed downstream of the EOP 62. In the EOP, the fluidic pressure is P6. In this example, the voltage between 1 to 25 V is applied to the EOP 60, which results in increasing the fluidic pressure P4. Once the pressure P4 exceeds the valve opening pressure, the check valve 64 opens to the channel results in releasing of the fluid 1 to the channel 68 and exits through the outlet 70. The EOP 62 remains inactive at 0 V and the fluid 2 remains intact in the reservoir 58. [00117] FIG. 9B illustrates another exemplary embodiment of a system 76, wherein the check valve 74 actuates to release the fluid 2 depending on the requirement of fluid 2 in the channel 68. FIG. 9B shows, the system 76 which comprises two reservoirs 56 and 58. The reservoirs 56 and 58 hold fluid 1 and fluid 2 with fluidic pressures P3 and P4 respectively. The reservoir 56 is connected with an EOP 60, and the check valve 72 (closed form) is placed downstream of the EOP 60. The fluidic pressure in EOP 60 is P5. The microfluidic channel is connected to both of the chambers 56 and 58 and has an outlet 70. The reservoir 58 is connected to the EOP 62, and the check valve 74 (open form) is placed downstream of the EOP 62. In this example, the voltage between 1 to 25 V is applied to the EOP 62, which results in increasing the fluidic pressure P6. Once the pressure P6 exceeds the valve opening pressure, the check valve 74 opens to the channel 68, which results in releasing of the fluid 2 to the channel 68 and exits through the outlet 70. The EOP 60 remains inactive at 0 V, and the fluid 1 remains intact in the reservoir 56. This concept may be expanded to include multiple EOP-operated valves in parallel or in series.

[00118] The actuation of similar type of check valve as illustrated in FIGs 9A and 9B, which requires at least 1 .4 PSI pressure as shown in a graph 78 in FIG. 10. The operating pressure for this type of check valves 77 (FIG. 10), in general, is greater than 1 PSI . The schematic in figure 1 1 illustrates the approximate/relative sizes of the actuating EOP stack 84 and battery power source 90, compared to a Biacore-type pinch valve 86 (inset 84). The valve, actuator, and power source are all self-contained on the device, unlike traditional microfluidic valve and control structures that require pneumatic control lines, external pressure sources, or high voltage power supplies.

[00119] In one or more embodiments, a microfluidic device comprises one or more valves, and one or more EOPs, wherein one or more of the valves are operatively coupled to one or more of the EOPs. In some embodiments of the device, one or more of the EOPs are operatively coupled to one or more reservoirs comprising fluids. In some other embodiments of the device, the valve is operatively coupled to one or more reagent compartments comprising dried or liquid buffers or reagents, such that, an operation of the valve enables dissolution of the buffers or reagents. The buffer or reagents after dissolution may further flow through downstream components of the device. In one embodiment of the device, the reagent compartments are placed in series with the pumps. In one or more embodiments, the dried buffer or reagents are configured to be rehydrated and reconstituted by the fluid.

[00120] FIG. 1 1 shows an integrated structure of a system 80 comprising three components, power and fluid source 82, high pressure EOP 84 and microfluidic channel 86 comprising a valve. In one or more exemplary embodiments, the integrated system 80 may be a microfluidic device. The power and fluid source 82 comprises stacked disks 96. The disk comprises power source with a switch 90, electrical contacts to the EOP 92 and a fluid reservoir 94. Each of the disks 96, has a diameter of 1 inch. The combined structure of 84 and 86 has magnified to show the EOP 100 with applied voltage 0, and another EOP 104 with applied voltage between 1 to 25 V. The check valve 102 is present downstream of the EOP 100, which is in a closed form. The check valve 106 is present downstream of the EOP 104, wherein the voltage between 1 -25 V is applied to increase the fluidic pressure of EOP 104 and the valve 106 is in the open form, which blocks the fluid flow through the microfluidic channel.

[00121] The state of the operatively coupled valve may be continuously altered by varying the pressure or flow output of the operably coupled EOP. The valve may be held in a static open or closed state by maintaining a constant set flow or pressure using a voltage or current control circuit. The valve state may also be continuously cycled from the open to closed state by either venting the pressure developed by the EOP, or reversing the EOP flow direction. The valve state may also be set at partially closed positions by controlling the exact pressure output of the EOP with respect to the valve actuation pressure requirements. The high pressure EOP may also be used to increase the valve pressure beyond the minimal valve actuation pressure, and minimizing leak flow to less the 0.1 % of the maximum or open forward flow.

[00122] The application of a potential across the EOPs enable the valves to actuate, which may results in rehydration and loading of reagents isolated in a storage chamber by each valve. Due to the ability of the EOPs to adjust pumping pressure, the disk may serve as the fluid drive for selective applications and may contain washing buffer, or elution buffer. The operating pressure for a simple check valve is > 1 PSI, whereas the pumping pressure generated using a single membrane EOP is about 0.7 PSI as shown in FIG. 3. Thus, the advantage of a multiple membrane stacked EOP is reflected herein, to generate significant amount of pressure, for example >1 PSI that is required for actuation of a simple valve. The actuation of silicone valves, such as valves in Biacore® system, require minimum operating pressure of ~ 4 PSI, which can be achieved using multiple membrane stacked EOP.

[00123] In one or more embodiments, a disposable disk contains EOP's, wherein each of the EOPs is capped with a highly absorbent cellulose membrane. The membranes, for one example, FTA® provide an ability to stabilize buffers and/or enzymatic reagents in the dehydrated form in the disk. In the disk (or cartridge), the cellulose membranes are impregnated with NaCI and different colored food dye. Each disk is fabricated by laminating the EOP stacks, and buffer storage disks into plastic cartridges. Each of the EOPs is also operatively coupled to a check-valve. [0100] The high pressure EOPs may then be used to selectively rehydrate dried reagents or buffer plugs downstream of the pump. Thus, simple running buffers or Dl water, may be used to run the pumps, and then rehydrate more complex components downstream. The high pressure output of the EOP stacks, enables rehydration of dense plugs of dehydrated materials, such as the salts associated with standard bio-analytical liquid solutions. The dehydrated plugs may also contain important reagents for bioassays, such as the Ready-to- Go® PCR reagents sold by GE. The elution profile for a specific device using green food dye is presented in FIG. 12. The graph 108 shows that the EOP pumping time, which is required to rehydrate the material reaches a plateau at about 5 seconds.

[0101] Each of the three different EOPs is coupled to the check valve shown in FIG. 10. Each check valve is isolating a different type of dehydrated buffer/reagent (Red, Green, and Blue food dye with NaCI), which is dried into three separate cellulose disks. The EOP that was operatively coupled to the cellulose disk containing green food dye was selected, and 20 volts was applied. Running buffer flowing through the EOP causes actuation of the check valve isolating that storage disk. The running buffer reconstitutes the buffer/reagents stored in that disk. The time required for mixing and exchange of the running buffer with the dried reagents is monitored by imaging the eluted fluid, and measuring the amount of green dye contained within the eluted fluid. The green dye concentration is measured using a standard digital camera by comparing pixel intensities as shown in FIG. 12, and presented as the percent pixel intensity compared to the clear running buffer (0), and the darkest ejected liquid (100).

EXAMPLE 1. Fabrication of EOPs

[00124] For this example, the need for metallization of each electroosmotic membrane in the EOP stack, assembly and handling of the electroosmotic membranes in a disposable cartridge, and manufacturing cost and fragility of the nanoporous membranes, were the primary challenges.

[00125] Materials: The anodisc® membranes are an in-house product (GE Healthcare), which are available in a package of 100 membranes. The silica membranes were created in- house by coating GE's anodisc® product with Si0₂ using either treatment in a sol-gel solution or deposition within an atomic layer deposition chamber. Silica sol gel was produced using raw materials from Sigma Aldrich, including TEOS (Tetraethyl orthosilicate), CAT# 86578- 250ml. ALD coating was performed using tris (tert-butoxy) silanol and trimethyl-aluminum as the precursors. Pt, Ag or Au electrodes were purchased from Good-fellow Cambridge Limited. The anodisc® membranes are used as bare anodisc® and also after the silica treatment, as shown in FIGs. 2A and 2B. The cellulose or paper sheets were acquired from Whatman™. A Keithley 2400 SourceMeter commercial power source and a disposable paper battery from power paper (supplied in a research agreement) were used as power sources.

[00126] EOP assembly was achieved by the method described below. An electrode was made of cellulose or paper, whereby large cellulose sheets (from Whatman™) were stretched within a metal frame, and saturated with a conductive polymer PEDOT:PSS, followed by drying. Alternatively, the electroosmotic membranes may be directly spin coated with PEDOT:PSS solution, followed by drying and etching. In other embodiments, a porous metal mesh was dip coated by PEDOT:PSS solution and dried. After a solvent treatment to render the PEDOT:PSS conductive and a brief drying period, electrodes were cut from the large sheet via laser machining or physical punching, and the paper electrodes were disposed between the alternating nanoporous ceramic membranes, as shown in FIG. 1 B. By this method, the metallization of the anodisc® which was required previously for creating EOPs, was replaced, and the paper electrodes were stacked using automated pick-and-place equipment. In addition, each anodisc® was cushioned between the cellulose electrode layers, providing a physical robustness to the EOP stack. This alternative arrangement of membranes and electrodes was laminated to form EOPs within plastic cartridges without damage to the fragile, internal ceramic membrane structure. A small 8 mm diameter EOP assembly was used. Each unit structure of EOP was primed with Dl water, mounted to a MEMS flow sensor, and a DC voltage was applied across each electroosmotic membrane using the paper electrodes within the stack.

[00127] After assembling of the EOPs, the integrated EOP was loaded into a plastic housing, and primed with a fluid, such as Dl water or borate buffer. Then the electrical battery terminals are attached to the electrode contacts in the membrane stack/EOP. Each alternating contact was attached to the positive, and then negative terminal on the battery respectively. An exact voltage from the Keithley power supply, or the direct voltage coming from a battery, was applied to the EOP. A MEMS flow sensor was placed in a series with the EOP, and flow rates were measured at the membrane stack exit. A back-pressure (from fluid column) was then applied to examine the maximum pumping pressure of the stack (the pressure at which the pump stalls, is considered the maximum pressure output from the EOP).

[00128] The flow rate of the EOP was monitored to check the pump efficiency. A brief burst at flow onset was due to the primed liquid exiting the capillary containing the MEMS sensor, however it quickly reaches a stable flow rate within seconds, as shown in FIG. 4.

EXAMPLE 2. Determination of stall pressure by increasing number of membranes

[00129] Experimental results were generated measuring the stall pressure of a single anodisc® EOP, and a double stack membrane using low-voltage, high pressure EOPs. Flow rates were measured using a commercial MEMS flow sensor as increased back pressure was applied to the pump. There was a 2X increase in pumping pressure within the double stack membrane, when compared to single membrane EOP, as shown in FIG. 3. The pumping pressures could be tuned to application-specific values based on the intelligent assembly scheme, as shown in FIG. 1 B. The flow rates were measured using a commercial MEMS flow sensor, Sensirion CMOSENS LG16-1000D, after the increased pressure load was applied to the pump. The pumping pressure may be increased or decreased according to the pressure requirement for specific applications by increasing or decreasing the number of membranes in the EOP.

EXAMPLE 3: EOP operation using various electrode materials

[00130] Most electroosmotic pumps work by passing hydrolyzed ions at the surface of the metal electrodes, thus releasing hydrogen and oxygen gas at the opposite ends of the nanopores of the membranes as described in FIG. 5A-5C. In three different EOPs, three different electrodes were selected. In the first example, a Pt electrode was used where a standard hydrolysis reaction took place using a standard hydrolysis driven pump. The flow rate is comparatively less in case of this EOP with Pt electrodes. The advantage of this EOP is the use of an inert electrode and standard pump configuration. Still, gas accumulation even at low driving voltages induces bubble formation and pH fluctuation, which is an increased burden in the dense nanoporous stacks, as shown in FIG. 5A. In the second example, silver oxide was used as the metal oxide electrode, as shown in FIG. 5B, where the redox reactions took place on the electrode surface which minimized the bubble formation and reduced the over potential. However, the disadvantages of this type of electrodes are limited coulombic capacity and the possibility of silver build up at the electrodes which may cause silver leaching to the electrolyte solution. In the third example, the conductive or redox polymer PEDOT/PSS was used as the electrodes. The PEDOT/PSS electrode had the same advantages of minimizing bubble formation without large over potentials due to hydrolysis. Instead, internal redox within the conductive polymer (PEDOT/PSS) coated paper electrodes provided an internal driving mechanism to drive ions and generate the current necessary to run the EOP, as shown in FIG. 5C. The voltage, which was applied on the PEDOT/PSS electrode, resulted in a redox reaction within the bulk of the material thus use of the high capacity cellulose as the electrode support substrate enabled increased coulombic capacity for driving the pump over longer periods of time. EXAMPLE 4. Determination of pumping rate using various electrode materials in the EOP stack.

[00131] Maximum flow rate of an EOP assembly using platinum mesh electrodes (0.06" diameter wires) between nanoporous AAO membranes (20 nm pore size) was determined (FIG. 6A), using the flow sensor described in Example 2. Maximum flow rate of an EOP assembly using Pedot:PSS saturated cellulose paper electrodes (0.5 mm paper thickness) between nanoporous AAO membranes (20 nm pore size) was determined. The increased pumping efficiency is due to both increased uniformity of the electric field (vs. the 0.06" mesh) and elimination of the over-potential required when using platinum (FIG. 6B). The flow rates were measured with no applied back pressure and thus represent the no load or maximum flow output for the EOP stack.

EXAMPLE 5 Determination of operating pressure range for actuation of valves.

[00132] A flow sensor was placed in a series connection with the check valve, and the flow was measured after applying the pressure in the forward and reverse directions, or in the closing or opening direction of the valve respectively. The key parameters measured including leak flow, where the flow rate was measured in the closed direction and forward flow rate was measured in the opened direction.

[00133] FIG. 10 graphically represents 78 efficiency of a check valve 77 using a pressure driven pump known in the art to determine operating pressure range for the check valve. The efficiency was derived from the flow ratio of leak flow and the forward flow. FIG. 10 illustrates a graph showing requirement of operating pressure for a simple check valve, which is > 1 PSI, while the pumping pressure of a single membrane EOP was measured about 0.7 PSI as shown in FIG. 3. However, the EOP with double stacked membrane generated pressure greater than 1 PSI, as shown in FIG. 3.

[00134] FIG. 10 shows the pressure requirement for actuating a check valve made from 0.5 mil kapton sheet. The size of the pore that the check valve sealed against was 400 μηη in diameter, and centered at the semi-circular end of the flap. The check valve flap is with 2 mm of arm length and diameter of 0.5 mm. The graph shows the flow rate ratio for pushing fluid through the check valve in the opened (F - forward) vs. closed (B - Backward or leak) direction. The operating range was deemed to be the point where the leak flow rate (B) was less that 0.1 % of the forward flow. Again, this operating pressure range is greater than the pressure output of standard low-voltage EOP.

[00135] The actuation of silicone valves (Biacore® system, alternate designs used by Fluidigm®) were also tested and found minimum operating pressure of ~ 4 PSI as shown in FIG. 8. Thus, this further demonstrated the broad applicability of removing complex pressure and power sources from fluidic systems via high pressure EOP actuation.

[00136] As an example, FIG. 8 shows the pressure requirement for actuating a version of the elastomeric microfluidic valve contained within GE's Biacore™ system with SPR based technology. A pressure was applied to the channel, and flow rate was measured with the valve open, and then after pressurizing the chamber behind the valve. As the valve closes and fluidic resistance increases, the flow rate through the channel drops. The valve shows full closure at 4 PSI, showing that actuation is not possible with standard low-voltage EOPs. In this example, the valve actuation fluid is separated from the fluid in the channel by the elastomeric valve.

[00137] Referring now to FIGs. 13 to 22 there is shown pre-charged EOPs and related graphs.

[00138] In these embodiments, a simplified structure of the EOP, which is alternatively referred to herein as "unit structure of EOP" or "unit of EOP", comprises at least two electroosmotic membranes and at least three pre-charged electrodes, wherein the electroosmotic membranes comprise one positive electroosmotic membrane and one negative electroosmotic membrane and the pre-charged electrodes comprise at least two cathodes and one anode or at least two anodes and one cathode. A unit EOP structure is illustrated in FIG. 13. The unit EOP is independent of an external power source, as in some embodiments, the electrodes are previously induced with the electric charges as pre-charged electrodes. In other embodiments, the electrodes may also be chargeable before use of the EOP. Both of the pre-charged or chargeable electrodes may be rechargeable.

[00139] As noted, for chargeable, rechargeable or pre-charged electrodes, the electrodes may be separately charged and then may be assembled in an EOP. In some embodiments, the electrodes present in an EOP are charged before use. In some embodiments, while charging the electrodes for storage, at least one membrane is interspersed between the two oppositely charged electrodes. The charged electrodes may then be assembled with multiple membranes to build a "battery free" EOP. For a battery free EOP, two charged electrodes are sufficient for pumping fluid, although additional electrodes may be used. In some embodiments, the charge is stored in three electrodes, which may further be utilized by using a unit of EOP, comprising at least two membranes and at least three electrodes. In some embodiments, multiple charged electrodes may be assembled with multiple membranes to form an integrated EOP comprising more than one unit EOP.

[00140] The plurality of porous electroosmotic membranes and electrodes are fabricated in a layer-by-layer configuration, wherein the alternatively charged membranes are stacked one after another, as shown in FIG. 14. In some embodiments, the electrodes are disposed on both sides of each of the membranes forming intervening layers between the stacked membranes. For example, a pre-charged electrode is disposed on the surface of a porous membrane, wherein the porous membrane is AAO or cellulose.

[00141] In one embodiment, a cathode is disposed on a negative electroosmotic membrane and an anode is disposed on the other side of the negative electroosmotic membrane, which results in the negative electroosmotic membrane to intersperse between the cathode and anode. In another embodiment, an anode is disposed on (upstream of) a positive electroosmotic membrane and a cathode is disposed on other side (downstream) of the positive electroosmotic membrane, such that the positive electroosmotic membrane is interspersed between the anode and cathode.

[00142] Various arrangements or rearrangements of the membranes and electrodes are possible, while maintaining alternatively charged membranes stacked with two oppositely charged electrodes on both sides of each of the membranes and keeping one electrode common between each of the two membranes. In one embodiment, only one of the cathodes or anodes is disposed between two oppositely charged electroosmotic membranes. For example, the unit structure of EOP have one anode which is common between a positive electroosmotic membrane and negative electroosmotic membrane, and results in a sequential disposition of a cathode, a positive electroosmotic membrane, an anode, a negative electroosmotic membrane, and then again another cathode. In another exemplary configuration, the unit EOP structure has one cathode which is common between the positive electroosmotic membrane and negative electroosmotic membrane, which results in a sequential disposition of an anode, a positive electroosmotic membrane, a cathode, a negative electroosmotic membrane, and then again, another anode.

[00143] As noted, in some exemplary embodiments, multiple units of EOPs are stacked together, wherein the multiple electroosmotic membranes and electrodes are arranged in alternative layers. Each of these layers remains electrically insulated due to the alternating anode/cathode arrangement, without physical insulation of the electrode material itself. In one example, a first unit of an EOP is followed by a second unit of an EOP, wherein the second unit of the EOP comprises a negative electroosmotic membrane that is disposed either upstream or downstream of the positive electroosmotic membrane of the first unit of the EOP. For example, in one embodiment, the negative electroosmotic membrane of the second unit of the EOP is disposed downstream of an anode of the first unit of the EOP, and a cathode is disposed on the directionally opposite side of the negative electroosmotic membrane, such that the membrane is interspersed between the anode and cathode. The interspersed negative electroosmotic membrane is further followed by a positive electroosmotic membrane, which is disposed downstream of the cathode, and an anode is further disposed on the directionally opposite side of the positive electroosmotic membrane to form the second unit of the EOP that is situated downstream of the first unit of the EOP. In some other embodiments, a third unit of an EOP is further formed downstream of the second unit of the EOP, a fourth unit of an EOP is further formed downstream of the third unit of the EOP, and so on. Hence, by stacking the multiple units of the EOPs, a single "integrated EOP" is generated, wherein the integrated EOP comprises multiple membranes and electrodes and the electrodes are present as intervening layers between each of the membranes.

[00144] The multiple units of the EOPs provide increasing pump surface area to the single integrated EOP, which generates higher pumping pressure without using complicated fabrication or higher input voltage. The stacking architecture thus enables high pressure pumping at low voltages, resembling a single unit of an EOP. Multiple low-voltage, high pressure EOPs may be used together in a series or in parallel.

[00145] An electrical double layer is formed in each alternating layer of the EOP and moves in the same direction through the membrane stack due to the alternating positive and negative electroosmotic membrane. Depending on the ionic concentration, the thickness of the electric double layer, which is referred to as the Debye length, varies from 3 nm to 300 nm for deionized water. The Debye length may become comparable to the nanopores within the EOP, depending on the electroosmotic membrane used. Furthermore, the use of thin membranes and corresponding interspersed electrodes enables the application of high electric field strengths across each of the alternating electroosmotic membranes. To increase pumping pressure, a larger surface area is required for double layer formation, without affecting field strength across the pores. In the EOP stack, the oppositely charged Debye layers move through the successive electric fields, and the net movement results in relatively higher electroosmotic pressure development due to the dense arrangement of the pores.

[00146] Polarity of the surface and zeta potential dictates the electroosmotic flow direction. The basic flow principle of EOPs is based on the surface charge of the membranes and the formation of electrical double layers. For example, when an aqueous solution contacts a glass surface (or silica), the glass surface becomes negative due to the deprotonation of surface silanol groups. An electrical double layer forms at the surface as a result of the deprotonation. The surface charge attracts dissolved counter-ions and repels co-ions, resulting in a charge- separation and forming an electrical double layer. The mobile ions in the diffused counter-ion layer are driven by an externally applied electrical field. The moving ions drag along the bulk liquid through the membranes and develop the electroosmotic flow. The EOP stack enables formation of a large surface area for electric double layer, without increasing the overall diameter of the pores or the electric field strength across each individual pore. Thus, higher pumping pressure is obtained without necessitating high driving voltage.

[00147] Unlike conventional pumps, one or more embodiments of the EOP generate high pressure at comparatively lower applied voltages, without the need for an external power source. The electroosmotic flow of the fluid builds up an electroosmotic pressure in the EOP using the potential energy stored in the electrodes. The pumping pressure may be tuned or modified based on the requirement of various applications. In some embodiments, the EOP is configured to generate a pressure of at least about 0.5 PSI. Unlike conventional single membrane EOPs which generate pressure between 0.1 and 0.75 PSI, multiple membrane- stacked EOP generates more pressure, in some embodiments, about 1 PSI. In one or more embodiments, using different membranes, such as anodic aluminum oxide (AAO) membrane, the pressure generated is at least about 0.75 PSI. In one embodiment, the EOP may generate a pressure of at least about 10 PSI, in another embodiment, the EOP may generate a pressure of about 100 PSI.

[00148] The amount of stored potential energy within the electrodes may be varied, however the capacity for storing potential energy is limited and depends on the redox potentials of the electrode materials used. In an exemplary embodiment, the EOP is configured to operate by applying at least 3 V potential across each of the membranes to achieve electric fields greater than 100 V/meter within the pump. In one example, the EOP is operated at 10 volts, in some other examples, the EOP is operated at less than or equal to 25 volts. As noted, the chemical potential for driving the EOP resides directly in the pump assembly, wherein the electrodes may be in a pre-charged, chargeable or rechargeable form.

[00149] One or more embodiments use pre-charged electrodes. In some embodiments, the pre-charged electrodes is used by chemically reducing/oxidizing a redox material prior to pump assembly. The pre-charged electrodes may be induced with charges before EOP operation, and after induced with charges, the electrodes are ready to be used upon application of pumping the fluids. In one or more embodiments, the electrodes comprise a material that generates a chemical potential of up to 3 V across the membranes. In one or more embodiments, the electrodes comprise a material capable of discharge slowly, for example, in a duration of 1 hour while running the pump with a flow rate between 0 and 10 μΙ_/η·Ήη/η"ΐη"ΐ². In some embodiments, the electrodes discharge in a duration of 1 hour while running the pump with a flow rate between 0 and 5 μΙ_/η"ΐίη/η"ΐη"ΐ².

[00150] In some other embodiments, the electrodes may be devoid of pre-induced charges, however, the electrodes are configured to be induced with charges before operation. Accordingly, the chargeable electrodes may be induced with charges at any point of time before operating the EOP, through either chemical or electrochemical procedures, such as, soaking with an oxidizing or reducing agent or directly injecting electric current using an external power source. In one embodiment, the chargeable electrodes are packaged in an EOP, wherein the electrodes are not pre-induced with charges, however may be induced with charges before use.

[00151] In one or more embodiments, the electrodes are rechargeable, wherein the electrodes are repeatedly chargeable. In some embodiments, the electrodes are rechargeable for up to 5000 times. For each of the rechargeable electrodes, the electrode has a life time. The rechargeable electrodes may prevent unwanted side reactions to increase the cycle lifetime. The life time of a rechargeable electrode means the ability of the electrode to be charged up for pumping fluids for a number of times, for example, may be for 5 times or 10 times, and after that the electrodes may not be chargeable.

[00152] In one or more embodiments, the pre-charged or chargeable or re-chargeable electrodes are made of conducting polymers. Typical conducting polymers include polythiophenes, polypyrroles and polyanilines. The conducting polymers may have discharge capacities of about 100mAh/g. The performance of the conducting polymers may be enhanced by the addition of nano-materials, such as carbon nanotubes. The discharge capacity may be increased by functionalizing the polymer with electroactive moieties. The conducting polymers may undergo fast redox reactions and consequently are capable of storing charge in the bulk material. Therefore, the conducting polymers are capable of performing redox reactions, and thereby the polymers may be referred to as redox polymer or pseudo-capacitors.

[00153] In one or more embodiments, the conducting polymer is an oxidation- reduction polymer material, metal oxide, graphene, or carbon nanotubes. In one embodiment, electrodes comprise a oxidation-reduction polymer or a redox polymer. The redox polymer or pseudo-capacitive materials may have advantages over carbon based super-capacitors in fast response time and superior specific energies, for example, the redox polymer may store a greater amount of energy per unit mass. The redox polymers may be more conductive than inorganic materials used in the batteries and consequently may have greater power generating capabilities. The redox conducting polymer or redox polymer, which has high conductivity, specific discharge capacity of greater than 200 mAh/g and a wide potential range with fast redox kinetics, are desirable for using as electrode material.

[00154] The redox polymers typically comprise spatially and electronically localized redox sites, unlike other conducting polymers. The redox sites are either covalently or electrostatically bound to the polymers. Two redox reactions may occur at the same potential at two different redox sites in redox polymers. Upon oxidation or reduction, the redox active molecule changes oxidation state without forming or disrupting any covalent bond, which minimizes the side reactions. The unwanted side reactions limit the charge storage of the electrodes, which affects the cycle lifetime of each of the pre-charged electrodes. The redox active molecules present in the electrode material undergo multiple cycles of oxidation /reduction reactions by conserving the overall charge and reducing the unnecessary side reactions.

[00155] In one or more embodiments, the redox polymer electrodes of the EOP are configured to maintain a long cycle lifetime. The redox polymers comprise a variety of materials, which cover a range of electrochemical potentials that results in a high voltage, however, the voltage may be selected in a range where the electrodes may not react irreversibly with solvents and electrolytes. Redox reactions generate redox complexes which are very stable having rapid electron transfer kinetics, and do not alter any chemical bonds during the electron transfer process. Therefore, the redox polymer electrodes may be discharged and recharged repeatedly without polymer degradation or polymer cracking. The electrochemical reversibility and the long-term integrity of the electrodes determine the utility and cycle lifetime of the electrodes for the battery free-EOP.

[00156] The composite electrodes of polymers with other materials may extend the cycle life time, improve conductivity, specific energy, and stability. Methods for improving cycle lifetime of conducting polymers are often limited by the swelling and consequent breakage of the polymer, and the method may include compositing with other materials, for example, carbon. In one or more embodiments, the electrode materials, such as redox polymers may form composites with other materials.

[00157] In some embodiments, the pre-charged electrodes include cathodes and anodes. One or more examples of the anode comprise an anode-active material, wherein the anode active material comprises a redox polymer charged to its reduced state. The anode may be employed in combination with various compatible electrolytes and cathodes in the EOP. The discharging mechanism in the electrodes involves electrochemical reactions at the redox polymer anode wherein the oxidation state of the anode changes to a higher oxidation state. For example, one of these electrodes may function as an anode when it is reduced from oxidation state (II) to the oxidation state (I) of a metal.

[00158] One or more examples of cathode include a cathode-active material, wherein the cathode-active material is a redox polymer in its oxidized state. The cathode may be employed with various compatible electrolytes and anodes in the EOP. The discharging mechanism in electrodes involves the electrochemical uncharging of the redox polymer cathode to a lower oxidation state. For example, an electrode functions as cathode when it is oxidized from the oxidation state (II) to the oxidation state (III) of the same metal or different.

[00159] In some embodiments, both the anode and cathode of the EOP comprise redox polymers. In one embodiment, the same redox polymer may be used for both the anode and cathode, in which case the redox polymer is oxidized on the cathode and reduced on the anode when the EOP is in its charged state. The redox polymer regains the same oxidation state on both the anode and cathode by discharging the electrodes. Starting from the discharged state, an electrode may be charged in either polarity, that is, either electrode may be employed as the anode. In an alternate embodiment, one redox polymer may be used for the anode and a different redox polymer may be used for the cathode. The method of chemically oxidized or reduced (p- or n-doped) polymer electrode before pump assembly thus eliminates the need for charging the polymers with an external voltage, which greatly enhanced the pump manufacturability.

[00160] In one or more embodiments, the electrode materials are macroporous, which allow transverse fluid flow. In some embodiments, the diameter of the macropores present on the electrodes may be in a range of 50 nm to 10 mm. In one embodiment, the diameter of the macropores is 1 mm. As noted, the electrodes are made of macroporous polymers, in some embodiments, the macroporous polymers may comprise glass or rubbery polymers, which maintain porosity in a dry state or when immersed in a solvent, may be used as electrodes. The macroporous polymers may include, but are not limited to, natural papers such as cellulose; synthetic paper such as polypropylenes or polyethylene, synthetic sponges such as polyethers, polyvinyl alcohol (PVA), or polyesters; or polymer mesh material such as polyurethane, polytetrafluoroethylene (PTFE), nylon, or polyethylene. In one embodiment, cellulose is used as electrodes, by soaking a paper in a conductive polymer.

[00161] In one or more embodiments, the redox polymers may include, but are not limited to poly(3,4-ethylenedioxythiophene) (Pedot): polystyrenesulfonate (PSS), Pedot-(molybdenum trioxide) Mo03, poly(3-(4-fluorophenyl)thiophene) (MPFT), poly(3-(4-fluorophenyl)-thiophene) (PFPT), poly(3-methyl thiophene) (PMeT) or poly(1 -cyano-2-(2-(3,4-ethylenedioxylthienyl))-1 - (2-thienyl)vinylene (ThCNVEDT) polymer. In some other embodiments, the electrode material may comprise pyridyl or polypyridyl complexes of transition metals like iron, ruthenium, osmium, chromium, tungsten and nickel. In some examples, the redox polymers may be selected from trisvinylbipyridine or bisbipyridine dichloride derivative of metal, orphyrins (either free base or metallo derivatives), phthalocyanines (either free base or metallo derivatives), metal complexes of cyclams, such as tetraazacyclotetradecane, metal complexes of crown ethers, metallocenes such as ferrocene, cobaltocene and ruthenocene. In one embodiment, the redox polymer is Pedot: PSS. The Pedot has good compatibility with polar group polymers while doped with polyanion such as PSS. In organic media, the Pedot: PSS material may have lesser tendency to swell, which may indicate a high ionic resistance and a slow electrochemical processability. The ionic conductivity of Pedot may be improved by blending with an ionic conductor, such as polyethyleneoxide (PEO).

[00162] In one or more embodiments, the polymeric material used, as structural support for the electrodes, or as coating for the electrodes, is selected from poly(olefins), halogenated poly(olefins), poly(cylco olefins), halogenated poly(cylco olefins), poly(styrenes), halogenated poly(styrenes), poly(propylenes), poly(ethylenes), halogenated poly(ethylenes), poly(tetrafluoroethylenes), polyacetylenes, polyphenylene vinylenes, polypyrroles, polythiophenes, polyanilines, polyphenylene sulfide or polyfluorenes poly(ether sulfones), poly(arylsulfones), poly(sulfones), poly(phenylene ether sulfones), poly(imides), poly(etherimides), poly(vinylidene fluorides), poly(esters), halogenated poly(esters), poly(ethylene terephthalates), poly(butylene terephthalates), poly(carbonates), polyvinyl halides), poly(acrylics), poly(acrylates), halogenated poly(acrylates), poly(methacrylics), poly(methacrylates), poly(anhydrides), poly(acrylonitriles), poly(ethers), poly(arylene ether ketones), poly(phenylene sulfides), poly(arylene oxides), poly(siloxanes), cellulose acetates, cellulose nitrates, poly(amides), nylon, ceramics and combinations thereof.

[00163] In some embodiments, the electrodes are made of a base material, such as a macroporous polymer, and coated with a conductive material. In one embodiment, the electrodes are coated with a redox polymer or a redox metal salt. In some embodiments, the electrodes are coated with redox polymers, which include but are not limited to Pedot, Pedot:PSS, poly(1 ,5-diaminoanthraquinone), poly(2-2-dithiodianiline) (pDTDA). The electrode may be coated with a conductive or redox polymer on a thick porous substrate.

[00164] In some embodiments, the redox polymer films or polymer coating on a substrate may be used as electrodes. Accordingly, the redox polymer films may be disposed on a metal or a non-metal substrate, wherein the film functions as an electrode. The electrode efficiency of the redox polymer film depends upon the diffusion layer as well as the thickness of the film. In one or more embodiments, the deposition of a film onto an electrode surface is through a spin-coating or dip-coating technique with a solution containing the redox polymers. The redox polymer film may be stably attached to the substrate, so that the redox complex formed in the reaction does not leach into the electrolyte solution. In one or more embodiments, the redox polymer may be deposited onto a glassy carbon or platinum electrode by electropolymerization resulting in a thin film of the polymer coating that functions as electrode.

[00165] In one embodiment of the EOP, the membranes and redox polymer electrodes are filled with deionized (Dl) water. The reduced and oxidized portions of the electrodes interact with each other through the Dl water filled in the nanopores. As noted, when the two charged redox polymer electrodes are coupled by a metal wire, such as 10 in FIG. 13, and an electron is allowed to flow through the metal wire 10 for each positive ion forms in the fluid of the EOP and passed through the nanopores 8 of the membrane (FIG. 13). The ionic flow through the membrane results electroosmotic flow induced by the stored chemical potential.

[00166] The chemical potential in the electrodes is generated without any input from the batteries or external power supplies. The electrodes comprise a material that is capable of storing chemical potential in electrodes, wherein the chemical potential generates a fluid flow through the membrane. In some embodiments, the chemical potential generated across the membrane is measured at nearly 1 V, for a specific electrode configuration. In one or more embodiments, stored charge at that potential is enough to cause 0.05 and 5 μΙ_Ληίη/η"ΐη"ΐ² electroosmotic flows through the membrane. The flow rate may be altered by varying the surface area of the pump, and thus, the number of nanopores within the EOP. In one or more embodiments, the electrodes are capable of discharging for about 1 hour, thus providing sustained electroosmotic flow with flow rates greater than or equal to 0.5 μΙ_Ληίη/η"ΐη"ΐ². The membranes are configured to operate the pump by applying an electric field of at least 100V/m across each of the membranes.

[00167] The chemical potential may be stored in the electrodes in a state that is dry, semi- dry or wet state. In a wet state, the EOP and electrodes are packaged in the running liquid, and flow is initiated by contacting oxidized and reduced electrodes, thus allowing discharge. In a semi-dry or gel state the electrodes are kept wet or hydrated to increase stability of their redox state electrode. In a dry state, the elecrodes are in redox state and the charge remains stable despite dehydration. Thus, electroosmotic flow of fluids may be iniated by either rehydrating the dried EOP unit comprising pre-chared electrodes, or closing the electrical circuit across the two pre-charged electrodes in a EOP packaged with its running liquid.

[00168] As noted, the chemical potential generates a fluid flow through the membrane, therefore, water or liquid, for example, in bio-assays, may flow through the EOPs without the need for control equipment. Each step within the assay may be programmed into the membrane itself, thus enabling a new fluidic control platform based on stored chemical potential, instead of active electrical or pneumatic controls. Various factors may be used to control and pre-program the complex fluidic manipulations to run the EOPs. The factors include, but are not limited to, the surface area of the EOPs, the magnitude of the stored charge, duration of the circuit to be closed to activate the pump, or electronic components such as resistors that may control the discharge rate of the pumps, and combinations thereof. [00169] As noted, the EOP is structured, so that each of the membranes is present between a positively charged electrode and a negatively charged electrode, eliminating the need for a semipermeable separator commonly associated with the conventional redox electrodes. As mentioned, each of the membranes may be interspersed between the two oppositely charged electrodes, such as a cathode and an anode, and each EOP unit within the stack is electrically isolated from the next. The configuration of the EOP, where each EOP unit within the stack is electrically isolated from the next, enables dense stacking of the nanoporous electroosmotic membranes, without changing the electric field strength across individual pores. For example, each of the anodes is disposed on one side of the electroosmotic membrane and each of the cathodes is disposed on the other side of the membrane.

[00170] In one or more embodiments, the membranes are porous, for example, macroporous, microporous or nanoporous. In some embodiments, the membranes are nanoporous with at least a 5% void space, which increases the efficiency. The diameter of the pores is typically between 10 nm to 500 nm. While stacking the membranes one after another, the pores of various membranes may be aligned in a straight line to form a continuous straight vertical channel starting from the top layer to the bottom layer, allowing a fluid to pass through the channels. In some embodiments, the pores of the various membranes may not be aligned in a straight line through the stacked membranes to form a straight channel. In these embodiments, although the pores are not aligned in a straight line, the fluid can still pass through the non-linear channels formed across multiple membranes.

[00171] Flow direction for positive electroosmotic membranes is different than that of the negative electroosmotic membranes. When the surface charge of the membrane is positive, the fluid flow proceeds in the direction of the electric field, and when the surface charge is negative, the fluid flow proceeds in the direction opposite to the electric field. The membranes may be stacked without individual electrical insulation. Therefore, the membranes are merged, with a common electrode in between two membranes, and the fabrication technique resolves any potential problem of individual electrical insulation, and increases the pressure using multiple membranes. The additive pressure in series results from the membrane stacking. In one or more embodiments, the EOP comprises 2 to 100 membranes.

[00172] The selection of electroosmotic membranes is typically restricted to a thin membrane, because the thin-nanoporous membrane structure increases the electric field strength at a given applied voltage. Each of the membranes has a thickness of about 10 nm to 10 mm. In one exemplary embodiment, 60 μηη thick bare or silica-coated AAO membranes are used in the EOP stack, wherein the interspersed electrodes comprise a thicker, porous paper substrate coated with a redox conductive polymer, where Pedot is disposed on the membrane surfaces. [00173] The membrane structure, composition or number of membranes stacked in the EOP or combinations of two or more may affect the pumping pressure of an EOP. Conventional single membrane or single element EOPs provide pumping pressure between 0.1 and 0.75 PSI. In one or more embodiments, using different membranes, such as an AAO membrane, the pressure generated is at least about 0.75 PSI. In some embodiments, by increasing the number of electroosmotic membranes in an EOP (or integrated EOP), the output pressure may be increased proportionally, as shown in FIG. 19. In one embodiment, the integrated EOP is configured to include multiple membranes stacked in a series to generate a pressure of at least about 10 PSI . In some other embodiments, the pressure is increased up to 100 PSI, by increasing the number of stacked membranes in an EOP. By stacking multiple units of EOPs to form an integrated EOP, which generates a high pressure independent of an external power source.

[00174] The composition of the electroosmotic membranes may vary. In some embodiments, the electroosmotic membranes comprise one or more dielectric materials or polymers with native or grafted ionizable functionalities to achieve zeta potential similar to the dielectrics, and combinations thereof. The dielectric materials may comprise, but are not limited to, tungsten oxide, vanadium oxide, silicon dioxide or silica, common glasses such as silicates, silicon carbide, tantalum oxide, zirconium oxide, hafnium oxide, tin oxide, manganese oxide, titanium oxide, silicon nitride, chromium oxide, aluminum oxide or alumina, zinc oxide, nickel oxide, magnesium oxide and combinations thereof.

[00175] In some embodiments, the electroosmotic membrane may be an insulator. In some embodiments, the electroosmotic membrane may comprise an oxide, metal oxide or a metal nitride. Any of the oxides, metal oxides or nitrides may be used in the membrane, and may comprise, but are not limited to, hafnium oxide, zirconium oxide, alumina_, or silica, as the insulators. The electroosmotic membranes may comprise polymers, selected from polydimethyl siloxane (PDMS), cyclic olefin copolymer (COC), polymethyl methacrylate (PMMA), poly carbonate (PC) or other materials with graftable surface chemistries.

[00176] Depending on the surface electric charge, the electroosmotic membranes may be divided in two types, positive electroosmotic membranes and negative electroosmotic membranes. In one embodiment, the positive electroosmotic membrane exhibits a negative zeta-potential under the same buffer/electrolyte conditions that create a positive zeta potential for alumina. For example, the positive electroosmotic membrane may comprise a material with a surface charge similar to silica in Dl water and the negative electroosmotic membrane may comprise a material with a surface charge similar to alumina in Dl water, and at a neutral pH. In some embodiments, the positive electroosmotic membrane comprises silica, a silicate material, polymeric material or a combination thereof. In some embodiments, positive electroosmotic membrane comprises any porous polymeric material exhibiting a similar zeta potential as silica. In one or more embodiments, the positive electroosmotic membrane comprises polyvinyledene fluoride, polycarbonate, polyester, mixed cellulose ester, nylon or polysulphone. In some embodiments, the negative electroosmotic membrane comprises an alumina material, titania or tantalum pentoxide. Some of the support polymers may be used as EOP membranes, for example, when the polymers are nanoporous and their surface charge is controlled. In one or more embodiments, the membranes may comprise PDMS, COC, PMMA, PC, and combinations thereof.

[00177] In one example of the EOP assembly, the AAO is selected as the membrane and cellulose is selected as the electrode, wherein the cellulose (or paper) electrodes are coated with a conductive liquid polymer, for example, Pedot:PSS. The AAO membranes are stacked by disposing multiple pieces of paper (cellulose) wetted with a conducting polymer solution as electrodes in between each of the AAO membranes. As noted, the EOP is configured to generate a transverse fluid flow through the AAO and paper stack.

[00178] In one embodiment, the electroosmotic membranes used in the EOPs are hydrophilic, which enables the membrane to wet out quickly and completely. The hydrophilic membranes eliminate the need for expensive pre-wetting treatment and increase the flow rate of the fluid passing through the membranes of the EOPs.

[00179] In one or more embodiments, the EOPs control the surface zeta potential of the membrane by embedding internal electrodes. For example, by embedding thin Pt electrode layers in the insulating membrane stack, the zeta potential of the surface of the membrane may be actively controlled. The zeta potential of the membrane may vary as a function of buffer, ionic strength and pH, and the surface characteristics. In one embodiment, the electroosmotic membrane has a zeta potential in a range of -100 mV to +100 mV. The magnitude of zeta potential for aluminum oxide in contact with 1 mM KCI, at pH=7 is 37 mV. The zeta potential for silica, zinc oxide, and zirconia is |f|=-80 mV; 45 mV and 90 mV, respectively.

[00180] The membranes are stacked to generate a pumping pressure that is proportional to a number of membranes in the pump. Therefore, by increasing the number of membranes, the EOPs are able to increase the operating pumping pressure. As noted, the basic unit structure of the EOP comprises at least two membranes, wherein the surface charges are opposite for two membranes at the time of the fluid flow through the membranes under the influence of the electric field. In some embodiments, the EOP comprises 2 to 100 membranes in series. The total output pressure increases proportionally to the number of membranes within the stack, and the pump is designed based on the application specific fluidic load. The efficiency of the EOPs may be changed, such as increasing or decreasing the pressure, according to the user's need.

[00181] FIG. 13 illustrates a simplified unit structure of battery-free EOP, which comprises at least one porous membrane, wherein the redox polymer electrodes 20, 22 are disposed on both sides of the each of the membranes 12, 16 and wherein one electrode is in oxidized state and the other one is in reduced state. The schematic drawing of the EOP of FIG. 13 further shows that the membrane 12/16 has a nonporous structure comprising a plurality of nanopores 8, wherein the oxidized state of the redox polymer functions as cathode 20 and the reduced state of the redox polymer functions as anode 22. The cathode 20 and anode 22 are operatively coupled by a wired connection 10. In one example of the unit structure of the battery-free EOP, each of the membranes is made of AAO with Pedot: PSS coated on both of the surfaces.

[00182] An exemplary low-voltage high-pressure EOP is developed by stacking multiple units of the EOP's to increase a pumping pressure in a portable fluidic system, which is illustrated in FIG. 14. The stacking arrangement of multiple membranes 24, as illustrated in FIG. 14, utilizes alternating nanoporous membranes 12 and 16 with opposing zeta potentials. Each of the membranes is interspersed between two oppositely charged redox polymer based pre-charged electrodes, such as cathode 20 and anode 22. For a stacked EOP, the intervening electrode layers are common, such as for first and second membranes 12 and 16, the intervening electrode is 22, for second and third membranes 16 and 12, the intervening electrode is 20, for third and fourth membranes 12 and 16, the intervening electrode is 22, and so on. The porous membranes and electrodes form channels, such as 28, wherein unidirectional electroosmotic flow is 30. The stacking pattern of the alternating membranes and intervening electrodes enables generation of a unidirectional flow 30 within the applied electric field 26.

[00183] The electrodes are operatively coupled to each other, the operative coupling of the electrodes triggers the pump to generate a transverse fluid flow through the membranes. In one or more embodiments, the pump comprises an activation mechanism comprising a manual or automated closure of a conductive path between all electrodes, or selected ones, within the stack. Therefore, the coupling of the selected electrodes leads the activation mechanism for the pump. In one example, the coupling may be automated using an activation switch, in some examples, manual coupling activates the pump. The operative coupling of two or more units of EOP generates a fluid-flow that is proportional to a number of the units of electroosmotic pump coupled in parallel. [00184] A schematic diagram of an example operation of an EOP assembly using Pedot:PSS saturated cellulose paper electrodes between nanoporous AAO membranes is shown in FIG. 15. The paper electrode has 0.5 mm paper thickness, and the AAO membranes are with 20 nm pore size. FIG. 15 reflects the use of the redox polymer to store charge across the nanoporous EOP material, and thus provide the electric field required to run the EOP. A voltage developed by the redox electrode within the EOP stack results in a passage of an ionic current through the electroosmotic membranes. For example, a voltage developed by the standard Pedot:PSS electrode results in a oxidation-reduction reactions on the electrodes, as shown in FIG. 15. In this case, the current passes across the membranes of the EOP due to the generation of ions by the reactions at the electrodes and the current that exists until reactive sites in the electrodes are exhausted.

[00185] To maintain a continuous fluid flow through the EOP, a closed circuit and stored chemical potential in the electrodes are used. The discharge of stored chemical potential may be utilized at the time of operating the EOP in a closed circuit, wherein the charged electrode is used as the power source. FIG. 16 is an example of a graph showing two different electroosmotic flow profiles across a 60 μηη nanoporous AAO membrane, wherein the Pedot:PSS electrodes are electrochemically reduced/oxidized, one for 10 min and another for 30 sec at 10 V, resulting in a different amount of charge storage in the self-contained EOP. The redox polymer electrodes are capable of discharging for about 1 hour (38) and for 25 min (36), when the electrodes are electrochemically charged for 10 min and 30 sec respectively. In this embodiment, the EOP is running with a steady flow rate (about 0.5 μΙ_Ληίη/η"ΐη"ΐ²) as shown in FIG. 16.

[00186] The size of the pump mainly depends on the size of the membranes on which the electrodes are typically deposited. The size of an EOP also determines the flow rate of a fluid through the pump. As the fluid passes through the pores of the membranes, therefore a greater number of pores increases the flow rate of the fluid. Therefore, a larger membrane surface area increases the flow rate of the EOP. FIG. 17 illustrates different flow rates from the self-contained EOPs, for differing surface areas. The larger surface area of an EOP contains a larger number of nanopores available for pumping, and thus provides a larger flow rate (42) when compared to an EOP with a smaller surface area (40).

[00187] The redox electrodes, for example Pedot:PSS electrodes, of the EOP have the ability to pump liquid, using the stored energy in a charged state when the electric circuit is closed, which results in a steady flow rate, 44 of FIG. 18. Once the circuit is opened, the fluid movement is discontinued through the membrane resulting in a drop in flow rate, 46 of FIG. 18. The flow begins after the circuit is reconnected, as shown in 48, FIG. 18. [00188] The efficiency of the EOPs may be changed, such as, by increasing or decreasing the pressure, or by changing the number of electroosmotic membranes. For example, the stall pressure of an EOP, comprising a double stack of an AAO and silica coated AAO (52), or an EOP comprising a four membrane stack of AAO and silica coated AAO (54) with pre-charged redox electrodes, is higher when compared to an EOP with a single AAO with the same electrodes (50), as shown in FIG. 19. The double stack membrane (52) results in a 2X increase in pumping pressure and the four membrane stacks (54) results in a 4X increase in pumping pressure. The flow rates, measured by a commercial micro-electromechanical systems (MEMS) flow sensor, decreases with increasing applied back pressure to the pump and the stall pressure is identified at the zero flow position. In one or more examples, at least two membranes are used to construct a single unit of EOP and this one unit of EOP generates pressure of about 2 PSI. In another example, an EOP constructed with 20 membranes generates a pressure of about 40 PSI.

[00189] In the EOPs, the fluid may be electroosmotically pumped through one or more membranes transversely. In one embodiment, the fluid is electroosmotically pumped between two membranes that are stacked one upon another, wherein the membranes are either directly in contact or spaced with a small distance of 1 mm or less. Larger distances within the EOP stack may decrease electric field strengths across the electroosmotic membranes, and therefore flow rates within the pump. Therefore, a pump may sustain high back pressure (e.g., >1 atm) and still maintain adequate fluid flow when a gap between two of the membranes is small, for an example, 500 μηη. The EOP of this embodiment increases the pumping pressure associated with low voltage EOPs, enabling use in field-able, self-contained, and battery- operated systems.

[00190] In one or more embodiments, the high pressure EOP may comprise a control circuit to maintain a constant current, voltage, fluid flow or pressure output during an operation. In one embodiment, the EOP comprises a controller to maintain a constant fluid flow. In one example, the controller comprises a micro controller circuit. One embodiment of the EOP assembly comprising a controller, as shown in FIG. 20.

[00191] In some embodiments, the membranes are further operatively connected to at least one fluid reservoir comprising fluid. In some other embodiments, the membranes are operatively connected to two reservoirs comprising fluids. In one example, the EOP assembly is coupled to one or more reservoirs, as shown in FIGs. 20, 21 and 22.

[00192] FIG. 20 illustrates an embodiment of an application 56 of the battery free EOP, wherein the EOP (60) is coupled to an upstream reservoir (58) and a downstream microfluidic channel 68. In one embodiment, a controller 62 is coupled to the EOP 60 to control the EOP operation. For example, the controller unit may comprise a microcontroller circuit. As noted, the EOP 60 is coupled to the microfluidic channel 68 by a connector 66 and valve 64. In operation, the fluid from the reservoir may pass through the EOP 60 and generate a pressure, which may actuate the valve 64/70. The actuation of valve prevents the fluid flow through the microfluidic channel 68, as the valve is in open form 70. Alternatively, when the valve is in closed form 64, the fluid 72 flows through the channel 68.

[00193] In one embodiment, the pumping liquid or fluid or working solution, which is used in the EOP has a pH from about 3.5 to 8.5. In an alternative embodiment, the pumping solution is a borate buffer with a pH of about 7.4 to 9.2 and an ionic strength between about 25 to about 250 mM.

[00194] In one or more embodiments, an EOP may be assembled with one or more reservoirs or chambers comprising fluids, wherein the fluids are different from the working fluid/liquid/solution of the EOP. For example, actuation of a membrane upon application (74) of pressure generated by the battery free EOP is illustrated in FIG. 21 , wherein a fluid pumped from a chamber upon membrane deflection. The EOP (60) is coupled to an upstream reservoir (58) and a downstream chamber/reservoir 80. As noted, the EOP 60 is coupled to the chamber 80 by a connector 66 and a membrane 76. In operation, the fluid from the reservoir may pass through the EOP 60 and generate a pressure, which may actuate the membrane 76 to the deflected form 78. The deflected form of the membrane 78 pushes the previously stored fluid in the chamber 80 to move forward towards the outlet 82. The previously stored fluid in the chamber 80 may be different from the fluid used for EOP operation, which is stored in reservoir 58.

[00195] In some other embodiments, multiple EOPs may be assembled with one or more reservoirs or chambers comprising fluids, wherein the fluids are different from the working fluid/liquid/solution of the EOP. For example, sequential actuation of multiple membranes upon application of pressure generated by the battery frees EOPs 100 is illustrated in FIG. 22. The chamber 80 contains a fluid, which flows from the chamber 80 through the outlet 82 upon operation of multiple EOPs, for example, the EOPs 60, 61 and 63 as per FIG. 22. The EOPs are coupled to an upstream reservoir (58) and a downstream chamber/reservoir 80. Each of the EOPs 60, 61 and 63 are connected to the chamber 80 through the membranes 84, 86 and 88 respectively. The fluid pumped from the chamber 80 upon membrane deflection in a sequential manner. In operation of the EOPs, the pressure is generated, which causes the deflection of the membranes and form 90, 92 and 94. The sequential actuation of membranes enables peristaltic pumping of the fluid through the chamber by pushing the stored fluid of the chamber 80 to move forward towards the outlet 82. [00196] Instead of deflection of the membranes 84, 86 and 88, in one embodiment, the membranes 84 and 88 may be deflected to generate over pressure, wherein the membrane 86 may generate under pressure because of EOP operation in backward direction, generating wave like motion for the fluid passes from the chamber 80 to outlet 82. In this embodiment, the membrane 84 pushes the fluid towards the outlet 82, the membrane 86 sucks the fluid in the direction of the reservoir 58 and then membrane 88 again pushes the fluid towards 82.

[00197] The core structure for the membrane and electrodes may be adapted to function with other pump components such as, for example, fluid chambers, inlet port(s), and outlet port (s). Moreover, high pressure EOPs may be coupled to one or more mechanical valves and switches, and used as an actuating pressure source, in contrast to a conventional fluid pump. Furthermore, implementation of such self-contained fluid control systems from a limited number of materials using simple fabrication techniques enable application of the portable pump and control elements within the disposable cartridges. Some more examples include, electroosmotic valves using the EOPs by opposing pressure driven flow, use of the EOPs to fill and empty flexible reservoirs to induce functionality via shape change and electroosmotic- actuators. A benefit for at least one of the embodiments is high throughput screening and compound profiling.

[00198] In one embodiment, the EOP is packaged with one or more pre-charged or chargeable or rechargeable electrodes to make the entire pump assembly be self-contained. The low voltage operation requires minimal current draw within each of the serially connected membranes of the EOPs. The multiple membrane-based EOPs generate higher pressures without a power supply.

[00199] The EOPs may also be integrated within micro-meter and millimeter scale fluidic systems by, for example, stacking them together to increase the pressure output or to maintain flow rate to overcome the viscous losses and pressure loads in long channels. The devices may be run on an electrode charge and can thus enable a variety of hand held devices.

[00200] An EOP assembly may be disposed in a channel to form an electroosmotic flow setup. The channel may be a microfluidic channel. In some examples, gas bubbles are released on the Pt electrode surface and impede flow through the EOP. However, in one embodiment of the multiple membrane-based EOP, stable flow rates of the fluid may be achieved within seconds, even when pumping into channels or structures with high hydraulic resistance. This is due to the high pumping pressure of the stacked EOPs and the fact that, the redox electrodes reduce bubble formation within the pump and therefore allow use of the EOPs in microchannels without interruption. [0201] A method of making an electroosmotic pump, comprises disposing a plurality of membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes in an alternative fashion to form a membrane stack; disposing a plurality of electrodes comprising cathodes and anodes, wherein the electrodes are pre-charged, chargeable, rechargeable or combination thereof and wherein at least one of the cathodes is disposed on one side of one of the positive electroosmotic membrane or negative electroosmotic membranes and at least one of the anodes is disposed on another side of that membrane, and at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane. The electrodes are operatively coupled to complete a circuit for activating the electrodes to generate a chemical potential across the membranes.

[0202] While making a redox polymer electrode, in one or more examples, a piece of porous membrane is soaked in a redox-polymer to form a redox-polymeric coating on the nanoporous membrane, wherein the redox-polymeric coating is used as an electrode layer on the membrane surface. For example, a cellulose membrane is soaked in the redox polymer Pedot:PSS and used as electrode. In one specific example, a piece of alumina oxide (Anodisc^®) membrane is encased in a redox polymer Pedot:PSS. The redox polymer is oxidized on one side of the membrane and reduced on the other; generating a chemical potential across the nanopores. For example, the Pedot is oxidized on one side of the membrane and is reduced on the other side, developing a chemical potential across the nanopores of the membrane.

[0203] In some embodiments, while making an EOP, the membranes are coated with polymeric material using various methods. In some embodiments, the AAO membrane is coated using a sol-gel material deposition, chemical vapor deposition (CVD) atomic layer deposition (ALD), or molecular vapor deposition (MLD). The fabrication techniques are used to produce the AAO membrane with an expected surface charge. For example, a bare AAO membrane contains a positive surface charge in water. In another example, the bare AAO membrane, is treated with silica to form the silica coated membrane that contains the negative surface charge in water. By selecting an appropriate surface coating material such as silica, the flow rate of the fluid passing through the membrane may be increased.

[0204] The battery-free EOP replaces the expensive platinum with conductive polymers as electrode material and led to the discovery that pre-charged redox polymers are used as batteries to power the pump. Embodiments of the battery-free EOP enable to develop a low- cost, disposable pump with an integrated power source, for use in point-of-care diagnostic devices. The applications for EOPs include, but are not limited to, lab-on-a-chip devices and applications, inkjet printing, ink delivery, drug delivery, liquid drug delivery, chemical analysis, chemical synthesis, proteomics, healthcare related applications, defense and public safety applications; medical applications, pharmaceutical or biotech research applications, environmental monitoring, in vitro diagnostic and point-of-care applications, or medical devices. In one embodiment, the EOPs may also be incorporated into MEMS devices. Other applications include, but are not limited to, PCR (DNA amplification, including real time PCR on a chip), electronic cooling (e.g. for microelectronics), pumping ionized fluids and colloidal particles, or adaptive microfluidic mirror arrays.

EXAMPLE 6. Fabrication of EOPs

[0205] Materials: The Anodisc® membranes (GE Healthcare), are available in a package of 100 membranes. The silica membranes were made by coating GE's Anodisc® membrane with Si0₂ using either treatment in a sol-gel solution or deposition within an atomic layer deposition chamber. Silica sol gel was produced using raw materials from Sigma Aldrich, including TEOS (Tetraethyl orthosilicate), CAT# 86578-250ml. ALD coating was performed using tris (tert-butoxy) silanol and trimethyl-aluminum as the precursors. Pedot:PSS electrodes were fabricated in-house using a solution purchased from Sigma-Aldrich, (St. Louis, MO). The Anodisc® membranes are used as bare Anodisc® and also after the silica treatment. Alternatively, in one example, nanoporous PVDF membranes were used in place of silica treated Anodisc® membranes, as the material share similar zeta potential. The cellulose or paper sheets were acquired from Whatman™. A Keithley 2400 SourceMeter commercial power source and a disposable paper battery from Power Paper Ltd. (Petach Tikva, Israel) were used as power sources.

[0206] EOP was assembled by using an electrode made of cellulose or paper, whereby large cellulose sheets (Whatman™) were stretched within a metal frame, and saturated with a conductive polymer PEDOT:PSS, followed by drying. Alternatively, the electroosmotic membranes may be directly spin coated with PEDOT:PSS solution, followed by drying and etching. In other embodiments, a porous metal mesh was dip coated by PEDOT:PSS solution and dried. After a solvent treatment to render the PEDOT:PSS conductive and a brief drying period, electrodes were cut from the large sheet via laser machining or physical punching, and the paper electrodes were disposed between the alternating nanoporous ceramic membranes, as shown in FIG. 14. By this method, the metallization of the Anodisc® which was used in other examples for making the EOPs, was replaced, and the paper electrodes were stacked using automated pick-and-place equipment. In addition, each Anodisc® was cushioned between the cellulose electrode layers, providing a physical robustness to the EOP stack. This alternative arrangement of membranes and electrodes was laminated to form EOPs within plastic cartridges without damage to the fragile, internal ceramic membrane structure. A small 8 mm diameter EOP assembly was used. Each unit structure of EOP was primed with Dl water, mounted to a MEMS flow sensor, and a DC voltage was applied across each electroosmotic membrane using the paper electrodes within the stack.

[0207] After assembling of the EOPs, the integrated EOP was loaded into a plastic housing and primed with a fluid, such as Dl water or borate buffer. A copper wire was used to connect the two oppositely charged electrodes. Then the wire terminals are attached to the two electrodes in the membrane stack/EOP. An exact voltage was derived from the redox electrodes, which was applied to the EOP. A MEMS flow sensor was placed in a series with the EOP, and flow rates were measured at the membrane stack exit. A back-pressure (from the fluid column) was then applied to examine the maximum pumping pressure of the stack (the pressure at which the pump stalls is considered the maximum pressure output from the EOP).

[0208] The flow rate of the EOP was monitored to check the pump efficiency. A brief burst at flow onset is due to the primed liquid exiting the capillary containing the MEMS sensor, however it quickly reaches a stable flow rate within seconds.

EXAMPLE 7. EOP operation using various electrode materials

[0209] The EOPs work by passing ions at the surface of the electrodes, through opposite ends of the nanopores of the membranes wherein, the electrons flow from oxidized to reduced electrodes as described in FIG. 15. In this example, the conductive or redox polymer PEDOT/PSS was used as the electrode. The PEDOT/PSS electrode has the advantages of minimizing bubble formation without large over potentials due to hydrolysis. In addition, internal redox within the conductive polymer (PEDOT/PSS) coated paper electrodes provided an internal driving mechanism to drive ions and generate the current necessary to run the EOP, as shown in FIG. 15. The voltage, which was applied on the PEDOT/PSS electrode, resulted in a redox reaction within the bulk of the material, thus use of the high capacity cellulose as the electrode support substrate enabled increased coulombic capacity for driving the pump over longer periods of time.

EXAMPLE 8. Charge storage capacity of redox polymer electrodes

[0210] The experiment was performed to determine the storage capacity of the redox polymer electrodes, by using Pedot:PSS electrodes in an EOP. The membranes were circular in shape and the area of the cellulose membranes was about 20 mm². The cellulose membranes were soaked in Pedot:PSS polymer solution. Due to the capacity of the cellulose (paper) membrane to retain liquid, the charge storage of a cellulose membrane might be more compared to other type of membranes. In one example, the electrodes were charged for about 10 min at about 10 V before using the electrodes in the EOP (38) and in another example, the electrodes were charged for about 30 sec at 10 V (36) as shown in FIG. 16. In the first example, the potential was generated of about 1 V and the flow 38 continued for about 1 hour with a constant flow rate of about 0.5 μΙ_/η"ΐιη (FIG. 16). In the second example, the flow 36 continued for only 25 min, while the electrodes were charged for 30 sec.

[0211] Therefore, the quantity of stored charge is one of the factors that determine the length of time for continuous flow in an EOP. The magnitude of charge of the electrode may be altered to change the flow rate, or the electrical resistance of the wire may be altered in order to change the discharge or flow time. The flow magnitude may be increased by storing more charge in the electrodes or by increasing the surface area of the membranes.

EXAMPLE 9: Determination of pumping efficiency using EOPs with membranes having different surface area

[0212] In this example, the electrodes were electrochemically reduced/oxidized which enabled separation of charge stored within the Pedot across the nanoporous EOP membranes. The flow rates were measured from two different self-contained EOPs with membranes having different surface area. Pedot:PSS electrodes were electrochemically reduced/oxidized for 10 min at 10 V. Two different AAO membranes were selected for the two EOPs, wherein one of the membranes had a 5 mm diameter and the another had a 10 mm diameter, resulting in different flow rates through the self-contained EOPs. FIG. 17 shows the bar graphs for flow rates from the two different EOPs with membranes of different surface areas. The larger surface area pump contains a larger number of nanopores available for pumping, and thus provides a larger flow rate 42, when compared to the flow rate from the smaller surface area pump 40. The AAO membrane/Pedot:PSS electrode established an average flow rate of 0.09 (μΙ_/η"ΐίη) per mm² of pump surface area.

EXAMPLE 10. Determination of pumping ability of an EOP stack using stored energy in the redox polymer electrode

[0213] The example demonstrates the ability of an EOP to pump liquid, using the stored energy in the redox polymer electrodes, in a charged state when the electric circuit was closed. Once the circuit was opened, the fluid movement was discontinued through the membrane. The flow began after the circuit was reconnected. The reconnection results in discharge of the chemical potential energy that was stored in the redox polymer electrodes as shown in FIG. 18.

[0214] The graph of FIG. 18 illustrates the change in flow rate of the fluid with time for an EOP driven by the discharge of the chemical potential stored in the redox electrodes. The graph shows a continuous flow 44 with a flow rate of -0.5 μί/ηΊΐη before disconnection of the wire, after disconnection of the wire the flow rate 46 was abruptly dropped to -0 μ-Jrmin, and after reconnection of the wire, the flow rate 48 again reached to -0.5 μ-Jrmin. Therefore, the wired-connection of two oppositely charged electrodes results fluid flow through the EOP due to the discharge of the stored chemical potential in the redox polymer electrodes, which was discontinued during disconnect of the electrodes and further continued on reconnection.

EXAMPLE 1 1 . Determination of stall pressure by increasing number of membranes

[0215] Results were generated measuring the stall pressure of an EOP comprising Anodisc® as membranes and Pedot: PSS as electrodes. A unit EOP, two units of stacked EOP, and four units of stacked EOP were used for this example, wherein the EOPs are low- voltage, high pressure EOPs. The pumping pressures may be tuned to application-specific values based on the intelligent assembly scheme, as shown in FIG. 14. The flow rates were measured using a commercial MEMS flow sensor, Sensirion CMOSENS LG16-1000D, after the increased pressure load was applied to the pump. The pumping pressure may be increased or decreased according to the pressure requirement for specific applications by increasing or decreasing the number of membranes in the EOP. Flow rates were measured using a commercial MEMS flow sensor as increased back pressure was applied to the pump. FIG. 19 shows increased pumping pressure realized by an embodiment of an EOP with multiple porous substrates, wherein each membrane was sandwiched by pre-charge electrodes of opposite charges. There was a 2X increase in pumping pressure within the double units of stacked EOPs (52) and 4X increase in pumping pressure within the four units of stacked EOPs (54), when compared to a single unit of EOP (50), as shown in FIG. 19. Therefore, two or more units of EOPs, which are operatively coupled, generated a fluid-flow that is proportional to a number of the units of EOP coupled in parallel.

[00216] While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the invention.

Claims

Claims:

1 . An electroosmotic pump, comprising:

a plurality of membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes;

a plurality of electrodes comprising cathodes and anodes, and

a power source;

wherein each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternately and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a postive electroosmotic membrane and negative electroosmotic membrane.

2. The electroosmotic pump of claim 1 , configured to operate by applying an electric field of at least 100V/m across each of the membranes.

3. The electroosmotic pump of claim 1 , configured to generate a pressure of at least about 0.75 PSI.

4. The electroosmotic pump of claim 1 , wherein the membranes are nanoporous.

5. The electroosmotic pump of claim 4, wherein the nanopores have a open dimension of between 10 to 500 nm.

6. The electroosmotic pump of claim 1 , wherein the membranes have a thickness of about 10 nm to 10 mm.

7. The electroosmotic pump of claim 1 , comprising 2 to 100 membranes.

8. The electroosmotic pump of claim 1 , wherein the membranes comprise tungsten oxide, vanadium oxide, silicon dioxide, silicates, silicon carbide, tantalum oxide, halfnium oxide, tin oxide, manganese oxide, titanium oxide, silicon nitride, chromium oxide, aluminum oxide, zinc oxide, nickel oxide, magnesium oxide and combinations thereof.

9. The electroosmotic pump of claim 1 , wherein the positive electroosmotic membrane comprises silica or silicate materials.

10. The electroosmotic pump of claim 1 , wherein the negative electroosmotic membrane comprises alumina materials.

1 1 . The electroosmotic pump of claim 1 , wherein the membranes comprise polymers, selected from PDMS, COC, PMMA, PC and combinations thereof.

12. The electroosmotic pump of claim 1 , wherein the electrodes are macroporous materials or thin films.

13. The electroosmotic pump of claim 1 , wherein the electrodes comprise a macroporous metal, conductive polymer, redox polymer, redox metal salt, metal oxide and combinations thereof.

14. The electroosmotic pump of claim 1 , wherein the electrodes and the membranes are configured to generate a transverse fluid flow through the membranes.

15. The electroosmotic pump of claim 1 is further configured to provide a pumping pressure that is proportional to a number of membranes in the electroosmotic pump.

16. The electroosmotic pump of claim 1 is further configured to provide a stack of two or more units of electroosmotic pumps, wherein a unit electroosmotic pump comprises one positive electroosmotic membrane and one negative electroosmotic membrane, at least a cathode and an anode and a power source,wherein the two or more unit of electroosmotic pumps are operatively coupled in parallel.

17. The electroosmotic pump of claim 16 is further configured to provide a fluid-flow, wherein a flow rate that is proportional to a number of the electroosmotic pump units in parallel.

18. The electroosmtoic pump of claim 1 , wherein the membranes are further operatively connected to at least two reservoirs comprising fluids.

19. An electroosmotic pump, as claimed in any one of the preceding claims, wherein said power source provides a voltage between about 0.1 to 25 volts, wherein the membranes and electrodes are operably coupled to said voltage to generate a pressure of at least about 0.75 PSI.

20. A method of actuating a valve, comprising:

operatively coupling the valve with an electroosmotic pump;

flowing a fluid through the electroosmotic pump ; and

generating a fluidic pressure of at least 0.75 PSI to actuate the valve,

wherein the electroosmotic pump comprises one or more thin, porous, positive electroosmotic membranes and one or more thin porous, negative electroosmotic membranes; a plurality of electrodes comprising cathodes and anodes, and a power source; wherein each of the positive and negative electroosmotic membranes are disposed alternately and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive and a negative electroosmotic membrane.

21 . The method of claim 20, wherein the fluidic pressure is about 0.75 to 30 PSI to actuate the valve.

22. The method of claim 20, wherein the fluidic pressure is about 30 to 100 PSI to actuate the valve.

23. The method of claim 20, wherein the fluidic pressure is generated by operating the electroosmotic pump by applying less than 25 volts across each of the membranes.

24. The method of claim 23, wherein the application achieves an electric field greater than 100 V/m across each electroosmotic membrane within the pump.

25. The method of claim 20, wherein the fluidic pressure is generated by using an electroosmotic pump comprising about 2 to 100 membranes.

26. The method of claim 20, wherein the fluid flows through the electroosmotic pump comprising nanoporous membranes.

27. The method of claim 1 , wherein the fluid flows through the electroosmotic pump with a flow rate of about 0.1 uL/min to 10 mL/min per cm² of surface area across the membranes.

28. The method of claim 20, wherein the fluid flows through the membranes having a thickness of about 10 nm to 10 mm for each individual membrane component.

29. The method of claim 1 , wherein the membranes comprise tungsten oxide, vanadium oxide, silicon dioxide/silica, common glasses/silicates, silicon carbide, tantalum oxide, halfnium oxide, tin oxide, manganese oxide, titanium oxide, silicon nitride, chromium oxide, aluminum oxide/alumina, zinc oxide, nickel oxide, and magnesium oxide; or, polymers with grafted or coated ionizable functionalities to achieve zeta potential similar to said dielectrics, and combinations thereof.

30. The method of claim 20, wherein the positive electroosmotic membranes comprise silica or silicate materials and the negative electroosmotic membranes comprise alumina materials.

31 . The method of claim 20, wherein the membranes comprise polymers, selected from PDMS, COC, PMMA, PC and combinations thereof.

32. The method of claim 20, wherein the electrodes comprise a macroporous metal, conductive polymer, redox polymer, redox metal salt, metal oxide and combinations thereof.

33. The method of claim 20, wherein the fluid flows through the electroosmotic pump in a transverse direction.

34. The method of claim 20, wherein the electroosmotic pump is further operatively coupled to at least one reservoir comprising the fluid.

35. The method of claim 20 wherein a voltage or current controller is used to control, vary or holds constant the fluid flow or pressure output from the electroosmotic pump.

36. The method of claim 35, wherin using the fluid flow or pressure output of the electroosmotic pump statically or dynamically varies the state of the operatively coupled valve.

37. The method of claim 35, where the fluid flow or pressure output of the electroosmotic pump is utilized to control a leak flow across the valve to less than 0.1 % of the maximum (forward, open valve) flow.

38. A microfluidic device, comprising:

one or more valves; and

one or more electroosmotic pumps, wherein the electroosmotic pumps comprise both positive electroosmotic membranes and negative electroosmotic membranes; a plurality of electrodes comprising cathodes and anodes, and a power source; wherein each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternately and wherein at least one of the cathodes is disposed on one side of one of the membranes and at least one of the anodes is disposed on other side of the membrane and wherein at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and a negative electroosmotic membrane;

wherein one or more of the valves are operatively coupled to one or more of the electroosmotic pumps.

39. The microfludic device of claim 38, wherein the or each electroosmotic pump has the features claimed in any one or more of claims 2 to 19

40. The microfludic device of claim 38 wherein said membranes are as defined in claim

41 . The microfludic device of claim 38, wherein one or more of the electroosmotic pumps are operatively coupled to one or more reservoirs comprising a fluid.

42. The microfludic device of claim 38, wherein the valve is operatively coupled to one or more reagent compartments comprising dried or liquid buffers or reagents, such that, an operation of the valve enables dissolution of the buffers or reagents.

43. The microfludic device of claim 42, wherein the reagent compartments are placed in series with the pumps.

44. The microfludic device of claim 42 or 43, wherein the dried buffer or reagents are configured to be selectively rehydrated and reconstituted by the fluid.

45. A pump, comprising:

a plurality of electroosmotic membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes; and a plurality of electrodes comprising one or more cathodes and one or more anodes; wherein the electrodes are pre-charged, chargeable, rechargable or combinations thereof and the cathode and anode are operatively coupled to each other, wherein the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternately,

wherein at least one cathode is disposed on one side of one of the membranes and at least one anode is disposed on another side of that membrane, and wherein at least one cathode or anode is disposed between a positive electroosmotic membrane and a negative electroosmotic membrane.

46. The pump of claim 45 configured to generate a pressure of at least about 0.75 PSI.

47. The pump of claim 45, wherein the electrodes comprise a material capable of generating a chemical potential up to 3 V across the membranes.

48. The pump of claim 45, wherein the electrodes comprise a material capable of discharging for about 1 hour while running the pump with a flow rate between 0 and 5 L/min/mm2 .

49. The pump of claim 45, wherein the electrodes are rechargeable up to 5000 times.

50. The pump of claim 45, wherein the electrodes comprise charges in a state that is dry, semi-dry or wet state.

51. The pump of claim 45, wherein the electrodes comprise a oxidation- reduction polymer material, metal oxide, graphene, carbon nanotubes and combinations thereof.

52. The pump of claim 45, wherein the electrodes comprise a poly(3,4- ethylenedioxythiophene):polystyrenesulfonate (Pedot-PSS), Pedot-(molybdenum trioxide) , poly(3-(4-fluorophenyl)thiophene) (MPFT), poly(3-(4-fluorophenyl)-thiophene) (PFPT), poly(3-methyl thiophene) (PMeT) or poly(1-cyano-2-(2-(3,4-ethylenedioxylthienyl))-1-(2- thienyl)vinylene (ThCNVEDT), PDTT polymer and combinations thereof.

53. The pump of claim 45, further compising a micro controller circuit to maintain a constant current, voltage, fluid flow, pressure output or combinations thereof.

54. The pump of claim 45, wherein the membranes are configured to generate an electroosmotic flow of about 0.05 to 5 ML min/mm2.

55. The pump of claim 45, wherein the membranes comprise nanopores having a diameter between 10 to 500 nm.

56. The pump of claim 45, wherein the membranes are configured to operate the pump by applying an electric field of at least 100V/m across each of the membranes.

57. The pump of claim 45, wherein the membranes have a thickness between 10 nm to 10 mm.

58. The pump of claim 45, comprising 2 to 100 membranes.

59. The pump of claim 45, wherein the membranes comprise a tungsten oxide, a vanadium oxide, a silicon dioxide, a silicate, a silicon carbide, a tantalum oxide, a halfnium oxide, a tin oxide, a manganese oxide, a titanium oxide, a silicon nitride, a chromium oxide, an aluminum oxide, a zinc oxide, nickel oxide, a magnesium oxide and combinations thereof.

60. The pump of claim 45, wherein the positive electroosmotic membrane comprises a silica, a silicate material, polymeric material or a combination thereof.

61. The pump of claim 45, wherin the positive electroosmotic membrane comprises polyvinyledene fluoride, polycarbonate, polyester, mixed cellulose ester, nylon, polysulphone and combinations thereof.

62. The pump of claim 45, wherein the negative electroosmotic membrane comprises an alumina material, titania or tantalum pentoxide.

63. The pump of claim 45, wherein the operative coupling of the electrodes is a trigger mechanism for a transverse fluid flow through the membranes.

64. The pump of claim 45, wherein the fluid-flow is proportional to a number of the units of electroosmotic pump coupled in parallel.

65. The pump of claim 45, wherein the membranes are stacked to generate a pumping pressure that is proportional to a number of membranes in the pump.

66. The pump of claim 45, comprising a stack of two or more unit electroosmotic pumps, wherein each unit electroosmotic pump comprises one positive electroosmotic membrane and one negative electroosmotic membrane, and at least one cathode and one anode, wherein the two or more unit electroosmotic pumps are operatively coupled in parallel.

67. The pump of claim 45, wherein the membranes are operatively connected to at least one fluid reservoir.

68. The pump of claim 45, wherein the pump comprises an activation mechanism comprising a manual or automated closure of a conductive path between all electrodes, or selected ones, within the stack.

69. The pump of claim 45, wherein the electroosmotic membranes are operatively coupled to a mechanical valve, a membrane, a diaphram and combination thereof.

70. The pump of claim 1 is further operatively coupled to a separate reservoir, chamber, or channel via a flexible membrane for pumping a fluid from the reservoir, chamber, or channel by actuation of the membrane.

71. A pump, comprising:

a plurality of electroosmotic membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes, wherein each of the positive electroosmotic membranes and negative electroosmotic membranes are disposed alternately;

a plurality of electrodes comprising one or more cathodes and one or more anodes, wherein the electrodes are pre-charged, chargeable, rechargable or combinations thereof and the cathode and anode are operatively coupled to each other,

wherein at least one cathode is disposed on one side of one of the membranes and at least: one anode is disposed on another side of that membrane,

wherein at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane, and

wherein the electrodes are operatively coupled to generate and store a voltage of up to 3 V volts to generate a pressure of at least about 0.75 PSI.

72. A method of making a pump, comprising:

disposing a plurality of membranes comprising one or more positive electroosmotic membranes and one or more negative electroosmotic membranes alternately to form a membrane stack;

disposing a plurality of electrodes comprising cathodes and anodes, wherein the electrodes are pre-charged, chargeable, rechargable or combination thereof and wherein at least one of the cathodes is disposed on one side of one of the positive electroosmotic membrane or negative electroosmotic membranes and at least one of the anodes is disposed on another side of that membrane, and at least one of the cathodes or anodes is disposed between a positive electroosmotic membrane and negative electroosmotic membrane, and

operatively coupling the electrodes to complete a circuit adapted to activate the electrodes.

73. The method of claim 72, wherein the chemical potential across two adjacent electrodes generates a voltage of up to 3 volts.

74. The method of claim 72, wherein the electroosmotic pump is further configured to generate a pressure of at least about 0.75 PSI.