EP1458977A1

EP1458977A1 - Peristaltic micropump

Info

Publication number: EP1458977A1
Application number: EP03792417A
Authority: EP
Inventors: Martin Richter; Martin Wackerle; Yücel CONGAR; Julia Nissen
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2002-08-22
Filing date: 2003-08-22
Publication date: 2004-09-22
Anticipated expiration: 2023-08-22
Also published as: DE10238600A1; AU2003255478A1; JP2005536675A; DE50300465D1; CN1675468A; US20050123420A1; US7104768B2; EP1458977B1; WO2004018875A1; JP4531563B2; EP1458977B2; CN100389263C

Abstract

The invention concerns a peristaltic micropump comprising a first membrane zone (12) provided with a first piezoelectric actuator (22) for actuating said first membrane zone (12), a second membrane zone (14) provided with a second piezoelectric actuator (24) for actuating said second membrane zone (14), and a third membrane zone (16) provided with a third piezoelectric actuator (26) for actuating said third membrane zone (16). A pump body (30) forms, with the first membrane zone (12), one first valve (62) whereof the passage orifice (32) is open when the first membrane zone (12) is not actuated and is closed when the first membrane zone (12) is operating. The pump body (30) forms, with the second membrane zone (14), a pumping cavity (42) whereof the volume decreases when the second membrane zone (14) is operating. Said pump body (30) forms, with the third membrane zone (16), a second valve (64) whereof the passage orifice (34) is open when the third membrane zone (16) is not actuated and is closed when the third membrane zone (16) is operating. The first and second valves (62, 64) are in fluid connection with the pumping cavity (42).

Description

Peristaltic micropump

description

The present invention relates to a micropump and, in particular, to a micropump that works according to a peristaltic pumping principle.

Micropu pen that work on a peristaltic pumping principle are known from the prior art. For example, the article “Design and Simulation of an implantable medical drug delivery system using microelectromechanical Systems technology” by Li Cao et al., Sensors and Actuators, A94 (2001), pages 117 to 125, deals with a peristaltic micropump, some Inlet, three pumping chambers, three silicon membranes, three normally closed active valves, three piezo stack actuators made of PZT, microchannels between the pumping chambers and an outlet.The three pumping chambers are of the same size and are etched in a silicon wafer.

A peristaltic micropump is also known from WO 87/07218, which has three membrane areas in a continuous substrate surface. A pump channel, which is connected to a fluid supply, is formed in a carrier layer which carries the substrate and an associated support layer. A transverse rib is formed in the pump channel in the area of an inlet valve and an outlet valve, on which an associated membrane section rests in the unactuated state in order to close the inlet valve and the outlet valve in the unactuated state. The third membrane area, which can also be operated separately, is arranged between the separately actuatable membrane areas assigned to the inlet valve and the outlet valve. By actuating the third membrane area, the chamber volume between the two valve areas is increased. Thus, by a corresponding time controlled actuation of the three membrane areas a peristaltic pumping action between the inlet valve and the outlet valve can be achieved. According to WO 87/07218, the actuator element consists of a three-way composite made of a metal membrane, a continuous ceramic layer and a segmented electrode arrangement. The ceramic layer has to be segmented polarized, which is technically difficult. Such a segmented piezo bending element is therefore complex and allows only small stroke volumes, so that such a pump cannot work in a bubble-tolerant and self-priming manner.

DE 19719862 A1 discloses a mini membrane pump that does not operate on the peristaltic principle, in which a pump membrane adjacent to a pump chamber can be actuated by a piezo actuator. A fluid inlet and a fluid outlet of the pump chamber are each provided with passive check valves. According to this document, the compression ratio of the micropump, i.e. H. the ratio of the stroke volume of the pump membrane to the total pump chamber volume is set depending on the maximum pressure value, which is dependent on the valve geometry and the valve wetting, and which is necessary to open the valves, in order to enable bubble-tolerant, self-priming operation of the micromembrane pump there.

In addition to the above-mentioned piezo actuators, it would also be possible to implement micropumps using electrostatic actuators, but electrostatic actuators only allow very small strokes. Alternatively, the implementation of pneumatic drives would also be possible, which, however, requires a high level of effort with regard to external pneumatics and the switching valves required for this. Pneumatic drives thus represent complex, expensive and space-intensive processes to implement a membrane deflection. The object of the present invention is to provide a peristaltic micromembrane pump which can be constructed in a simple manner and which enables bubble-tolerant, self-priming operation.

According to the invention, this object is achieved by a peristaltic micropump according to claim 1.

The present invention provides a peristaltic microscope with the following features:

a first membrane area with a first piezo actuator for actuating the first membrane area;

a second membrane area with a second piezo actuator for actuating the second membrane area;

a third membrane area with a third piezo actuator for actuating the third membrane area; and

a pump body which, together with the first membrane area, forms a first valve, the passage opening of which is open when the first membrane area is not actuated, and whose passage opening can be closed by actuating the first mechanical area, which together with the second membrane area forms a pump chamber, the volume of which can be reduced by actuating the second membrane area, and which, together with the third membrane area, forms a second valve, the passage opening of which is open when the third membrane area is not actuated, and whose passage opening can be closed by actuating the third membrane area,

wherein the first and second valves are fluidly connected to the pump chamber.

The present invention thus provides a peristaltic micropump in which the first and the second valve are in the actuated state are open, and in which the first and the second valve can be closed by moving the membrane towards the pump body, while the volume of the pump chamber can also be reduced by moving the second membrane region towards the pump body.

With this construction, the peristaltic micropump according to the invention enables the realization of bubble-tolerant, self-priming pumps, even when piezo elements arranged on a membrane are used as the piezo actuator. Alternatively, so-called piezo stacks (piezo stacks) can also be used according to the invention as piezo actuators, which, however, are disadvantageous compared to piezo diaphragm transducers in that they are large and expensive, problems with the connection technology between the stack and diaphragm and problems with the adjustment of the stacks deliver and are therefore associated with a higher effort.

In order to ensure that the peristaltic micropump according to the invention can operate in a bubble-tolerant and self-priming manner, it is preferably dimensioned such that the ratio of stroke volume and dead volume is greater than a ratio of delivery pressure and atmospheric pressure, the stroke volume being the volume that can be displaced by the pump membrane. the dead volume is the volume remaining between the inlet opening and outlet opening of the micropump when the pump diaphragm is actuated and one of the valves is closed and one is open, the atmospheric pressure is a maximum of approximately 1050 hPa (worst-case consideration), and the delivery pressure is in the Fluid chamber area of the micropump, ie in the pressure chamber, is necessary pressure to a liquid / gas interface at a point which is a flow restriction in the microperistaltic pump, ie between the pump chamber and the passage opening of the first or second valve, including this passage opening. represents moving past. If the ratio of stroke volume to dead volume, which can be referred to as the compression ratio, satisfies the above condition, it is ensured that the peristaltic micropump operates in a bubble-tolerant and self-priming manner. This applies both when using the peristaltic micropump for conveying liquids when a gas bubble, usually an air bubble, gets into the fluid area of the pump, and when using the micropump according to the invention as a gas pump, when moisture inadvertently condenses from the gas to be conveyed and thus a gas / liquid interface can occur in the fluid area of the pump.

Compression ratios that meet the above condition can be achieved according to the invention, for example, by making the volume of the pump chamber larger than that of valve chambers formed between the respective valve membrane regions and opposite pump body sections. In preferred exemplary embodiments, this can be achieved in that the distance between the membrane and the surface and the pump body surface is greater in the region of the pump chamber than in the region of the valve chambers.

A further increase in the compression ratio of a peristaltic micropump according to the invention can be achieved by adapting the contour of a pump chamber structured in the pump body to the bending line of the pump membrane, ie the curved contour thereof in the actuated state, so that the pump membrane in the actuated state essentially does this can displace the entire volume of the pump chamber. Furthermore, the contours of valve chambers formed in the pump body can also be adapted correspondingly to the bending line of the opposite membrane sections, so that, in the optimum case, the actuated membrane area displaces essentially the entire valve chamber volume in the closed state. Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

1 shows a schematic cross-sectional view of an exemplary embodiment of a peristaltic micropump according to the invention in a fluid system;

2a to 2f are schematic representations to explain a piezo diaphragm transducer;

3a to 3c are schematic cross-sectional representations to explain the terms stroke volume and dead volume;

Fig. 4 is a schematic diagram showing the volume / pressure tensile levels during a pumping cycle;

5a to 5c are schematic representations for explaining the term delivery pressure;

6a to 6c are schematic views of an alternative exemplary embodiment of a micro pump according to the invention;

Fig. 7 is an enlarged view of a portion of Fig. 6b;

FIG. 8 is an enlarged schematic cross sectional view of a modified area of FIG. 7;

9a, 9b and 9c show schematic representations of possible pump chamber designs;

10a and 10b are schematic representations of an alternative exemplary embodiment of a micropump according to the invention; 11 to 13 are schematic cross sectional views of enlarged portions of modifications of the example shown in Figs. 10a and 10b;

14 shows a schematic cross-sectional view of a further alternative exemplary embodiment of a micropump according to the invention;

15 shows a schematic illustration of a multiple micropump according to the invention; and

16 shows a schematic illustration of an alternative exemplary embodiment of a micro pump according to the invention.

A first exemplary embodiment of a peristaltic micropump according to the invention, which is integrated in a fluid system, is shown in FIG. 1. The micromembrane pump comprises a membrane element 10 which has three membrane sections 12, 14 and 16. Each of the membrane sections 12, 14 and 16 is provided with a piezo element 22, 24 and 26 and forms together with the same a piezo membrane transducer. The piezo elements 22, 24, 26 can be glued to the respective membrane sections or can be formed on the membrane by screen printing or other thick-film techniques.

The outer surface of the membrane element is joined to a pump body 30 so that there is a fluid-tight connection between them. Two fluid passages 32 and 34 are formed in the pump body 30, one of which, depending on the pumping direction, represents a fluid inlet and the other a fluid outlet. In the exemplary embodiment shown in FIG. 1, the fluid passages 32, 34 are each surrounded by a sealing lip 36.

Furthermore, in the embodiment shown in FIG. 1, the underside of the membrane element 10 and the top of the Pump body 30 structured to define a fluid chamber 40 therebetween.

In the exemplary embodiment shown, both the membrane element 10 and the pump body 30 are implemented in a respective silicon wafer, so that they can be joined to one another, for example by silicon fusion bonding. As can be seen in FIG. 1, the membrane element 10 has three recesses in the upper side thereof and one recess in the lower side thereof in order to define the three membrane regions 12, 14 and 16.

The diaphragm sections 12, 14 and 16 can each be actuated in the direction of the pump body 30 by the piezoelectric ducks or piezoceramics 22, 24 and 26, so that the diaphragm section 12 together with the fluid passage 32 represents an inlet valve 62 which can be actuated of the membrane section 12 can be closed. In the same way, the membrane section 16 and the fluid passage 34 together constitute an outlet valve 64, which can be closed by actuating the membrane section 16 by means of the piezo element 26. Finally, the volume of the pump chamber region 42 arranged between the valves can be reduced by actuating the piezo element 24.

Before going into the mode of operation of the peristaltic micropump shown in FIG. 1, the fluid system environment into which the micropump according to FIG. 1 is installed is briefly described. The pump is glued to a carrier block 50 with the pump body 30, wherein, as shown in FIG. 1, grooves 52 can optionally be provided in the carrier block 50 in order to absorb excess adhesive. The grooves 52 can, for example, be provided surrounding the fluid channels 54 and 56 formed in the carrier block 50 in order to absorb excess adhesive and to prevent it from getting into the fluid channels 54, 56 or the fluid passages 32, 34. The pump body 30 is glued or joined to the carrier block in such a way that the fluid id passage 32 in fluid communication with the fluid channel 54 and that the fluid passage is in fluid communication with the fluid channel 56. A further channel 58 can be provided in the carrier block 50 between the fluid channels 54 and 56 as a transverse leak protection. At the outer ends of the fluid channels 54, 56, connecting pieces 60 are provided which can be used, for example, for attaching hose lines to the fluid system shown in FIG. 1. Furthermore, a housing 61 is shown schematically in FIG. 1, which is joined to the carrier block 50, for example using an adhesive connection, in order to provide protection for the micropump and to seal the piezo elements moisture-tight.

To describe a peristaltic pump cycle of the pump shown in FIG. 1, it is initially assumed that there is an initial state in which the inlet valve 62 is closed, the pump membrane corresponding to the second membrane section 14 is in the unactuated state and the outlet valve 64 is open. Starting from this state, by actuating the piezo element 24, the pump diaphragm 14 is moved downward, which corresponds to the pressure stroke, whereby the stroke volume through the open outlet valve into the outlet, i.e. the H. the fluid channel 56 is promoted. The compression of the pump chamber 42 during the pressure stroke by the stroke volume leads to an overpressure in the pump chamber, which is reduced by the fluid movement through the outlet valve.

Starting from this state, the outlet valve 64 is closed and the inlet valve 62 is opened. The pump diaphragm 14 is then moved upward in that the actuation of the piezo element 24 is ended. The thereby expanding pump chamber leads to a negative pressure in the pump chamber, which in turn results in a suction of fluid through the opened inlet valve 62. Then the inlet valve 62 is closed and the outlet valve 64 is opened so that the above-mentioned initial state is reached again. The pump cycle described would thus result in a fluid volume that is essentially the stroke volume of the Diaphragm section 14 corresponds to, pumped from the fluid channel 54 to the fluid channel 56.

According to the invention, piezo membrane transducers or piezo bending transducers are preferably used as piezo actuators. Such a bending transducer achieves an optimum stroke if the lateral dimensions of the piezoceramic correspond to approximately 80% of the membrane underneath. Depending on the lateral dimensions of the membrane, which can typically have side lengths of 4 mm to 12 mm, deflections of several 10 μ strokes and thus volume strokes in the range from 0.1 μl to 10 μl can be achieved. Preferred exemplary embodiments of the present invention have volume strokes at least in such a range since bubble-tolerant peristaltic pumps can advantageously be realized with such a volume stroke.

It should be noted with piezo diaphragm converters that they only have an effective stroke downwards, i.e. H. to the pump body. In this regard, reference is made to the schematic representations of FIGS. 2a to 2f. FIG. 2a shows a piezoceramic 100, which is provided with metallizations 102 on both surfaces thereof. The piezoceramic preferably has a large d31 coefficient and is polarized in the direction of arrow 104 in FIG. 2a. According to FIG. 2a there is no voltage on the piezoceramic.

To generate a piezo diaphragm transducer, the piezoceramic 100 shown in FIG. 2a is now firmly mounted on a diaphragm 106, for example glued, as shown in FIG. 2b. The membrane shown is a silicon membrane, but the membrane can be formed by any other materials as long as it can be contacted electrically, for example as a metallized silicon membrane, as a metal foil or as a plastic membrane made conductive by a two-component injection molding. If a positive voltage, ie a voltage in the polarization direction, U> 0, is now applied to the piezoceramic, the piezoceramic contracts, see FIG. 2c. As a result of the fixed connection of the piezoceramic 100 to the membrane 106, the membrane 106 is deflected downward by this contraction, as is illustrated by arrows in FIG. 2d.

To cause the membrane to move upward, a negative voltage, i. H. a voltage against the direction of polarization to which piezoceramic is applied, as shown in FIG. 2e. However, this leads to a de-polarization of the piezoceramic even at low field strengths in the opposite direction, as indicated by an arrow 108 in FIG. 2e. Typical depolarization field strengths of lead zirconate titanate ceramics (PZT ceramics) are, for example, -4000 V / cm. Thus, upward movement of the membrane, i. H. in the direction of the piezoceramic, as indicated in FIG. 2f.

Despite this disadvantage in that, due to the asymmetrical nature of the piezo effect, only an active downward movement, ie towards the pump body, can be realized with the two-layer silicon-piezo bending transducer, ie the piezo diaphragm transducer of such a bending transducer is a preferred embodiment of the present invention, since this form of transducer has numerous advantages. On the one hand, they have a fast response behavior, on the order of about 1 millisecond with low energy consumption. Furthermore, scaling with dimensions of piezoceramic and membrane over large areas is possible, so that a large stroke (10 .... 200 μm) and a large force (switching pressures 10 ⁴ Pa to 10 ⁶ Pa) are possible, with a larger one Stroke the achievable force decreases and u reversed. Furthermore, the medium to be switched is separated from the piezoceramic by the membrane. If the peristaltic micropumps according to the invention are to be used in applications in which bubble-tolerant, self-priming behavior is required, the microperistaltic pumps must be designed in order to comply with a design rule with regard to the compression ratio, which defines the ratio of stroke volume to dead volume. For the definition of the terms displacement volume ΔV and dead volume V ₀ , reference is first made to FIGS. 3a to 3b.

3a schematically shows a pump body 200 with an upper surface thereof, in which a pump chamber 202 is structured. A diaphragm 204 is schematically shown above the pump body 200, which is provided with an inlet valve piezo actuator 206, a pump chamber piezo actuator 208 and an outlet valve piezo actuator 210. Piezoactuators 206, 208 and 210 allow respective areas of the membrane 204 to move downward, ie. H. towards the pump body 200, as shown by arrows in Fig. 3a. The line 212 in FIG. 3a furthermore shows the section of the diaphragm 204 opposite the pump chamber 200, i. H. the pump membrane, in its deflected, d. H. actuated by the pump chamber piezo actuator 208, state shown. The difference in the pump chamber volume between the undeflected state of the membrane 204 and the deflected state 212 of the membrane 204 represents the stroke volume ΔV of the pump membrane.

According to FIG. 3a, the channel regions 214 and 216 arranged under the inlet valve piezo actuator 206 and under the outlet valve piezo actuator 210 can be closed by actuating the corresponding piezo actuator in each case by the respective membrane regions resting on the regions below the pump body. Figures 3a to 3c are only rough schematic representations, the respective elements being designed in such a way that the respective valve openings can be closed. Consequently an inlet valve 62 and an outlet valve 64 are in turn formed.

3b shows a situation in which the volume of the pump chamber 202 is reduced by actuating the pump chamber piezo actuator 208 and in which the inlet valve 62 is closed. The situation shown in FIG. 3b thus represents the state after a quantity of fluid has been expelled from the outlet valve 64, the volume of the fluid region remaining between the closed inlet valve 62 and the passage opening of the open outlet valve 64 being the dead volume V ₀ with respect to the pressure stroke, as shown by the hatched area in Fig. 3b. The dead volume with respect to a suction stroke at which the inlet valve 62 is opened and the outlet valve 64 is closed is defined by the volume of the fluid region remaining between the closed outlet valve 64 and the passage opening of the opened inlet valve 62, as shown in FIG. 3c by the hatched region - shows is.

At this point it should be noted that the respective dead volume is defined from the respectively closed valve to the passage opening at which a substantial pressure drop takes place at the moment of a respective volume change of the pumping chamber. With a symmetrical construction of the inlet valve and outlet valve, as is preferred for a bidirectional pump, the dead volumes V ₀ for the pressure stroke and the suction stroke are identical. If there are different dead volumes due to an asymmetry for a pressure stroke and a suction stroke, then, in the sense of a worst-case scenario, it is assumed below that the larger of the two dead volumes is used to determine the respective compression ratio.

The compression ratio of the microperistaltic pump is calculated from the stroke volume ΔV and the dead volume V ₀ as follows: ε = ΔV / V ₀ . Eq. l

In the following, a worst case analysis is assumed, in which the entire pump area is filled with a compressible fluid (gas). The volume / pressure conditions that occur in the peristaltic pump during a peristaltic pump cycle as described above are shown in the diagram of FIG. 4. 4 each shows both the isothermal volume / pressure characteristic curves and the adiabatic volume / pressure characteristic curves. In the sense of a worst-case analysis, the following isothermal conditions, such as occur with slow changes in state, is assumed.

At the beginning of a pressure stroke, a pressure po prevails in the fluid region existing between the inlet valve and the outlet valve, while this region has a volume V ₀ + ΔV. Starting from this state, the pressure membrane moves downward by the stroke volume ΔV during the pressure stroke, as a result of which an overpressure pu forms in the fluid region, ie the pump chamber, so that a pressure of po + po prevails at a volume of Vo. The overpressure in the pumping chamber is reduced by conveying the air volume ΔV through the outlet until pressure equalization has taken place. This outflow of fluid from the outlet corresponds to the jump from the upper curve to the lower curve in FIG. At the end of the pressure equalization, there is a state po, Vo, which corresponds to the starting point of a suction stroke. Starting from this state, the membrane is moved away from the pump body, ie the volume of the pressure chamber expands by the stroke volume ΔV. 4 is changed to the state p ₀ ~ Pu / V ₀ + ΔV, which is referred to as the “suction stroke after expansion” in FIG. 4. Due to the negative pressure prevailing, a fluid volume ΔV is sucked in through the inlet opening until pressure equalization has taken place. The inflow 4 corresponds to the jump from the lower curve to the upper curve the pressure equalization therefore prevails in the state p ₀ , V ₀ + ΔV, which in turn corresponds to the starting point of a pressure stroke.

In the above general state considerations, which serve to explain the invention in general, the volume displacements of the inlet valve and outlet valve between the respective suction strokes and pressure strokes were neglected.

In order to be able to achieve a bladder tolerance, the overpressure po during the pressure stroke or the underpressure p _α during the suction stroke must exceed a minimum value during the pressure stroke or fall below it during the suction stroke. In other words, the pressure amount during the pressure stroke and the suction stroke must exceed a minimum value, which can be referred to as the delivery pressure p _F. This delivery pressure is the pressure in the pressure chamber which must at least prevail to pass a liquid / gas interface at a point which represents a flow restriction between the pump chamber and the passage opening of the first or second valve, including this passage opening move. This delivery pressure can be determined as follows depending on the size of this river constriction.

Capillary forces have to be overcome if free surfaces, for example in the form of gas bubbles (for example air bubbles) are moved in the fluid areas within the pump. The pressure that must be applied to overcome such capillary forces depends on the surface tension of the liquid at the liquid / gas interface and the maximum radius of curvature ri and the minimum radius of curvature r _{2 of} the meniscus of this interface:

The delivery pressure to be generated is defined by equation 2, namely at the point within the flow path of the microperistaltic pump at which the sum of the inverse radii of curvature r _x and r _{2 of} a liquid / gas interface with a given surface tension is maximum. This point corresponds to the river constriction.

For example, consider a channel 220 (FIG. 5a) with a width d, the height of the channel also being d. The channel 220 has a change in cross section at both channel ends 222, for example under the valve membrane or the pump membrane. 5a, the channel is completely filled with a liquid 224 which flows in the direction of arrow 226.

5b, an air bubble 228 now strikes the change in cross-section at the entrance to the channel 220. A wetting angle θ occurs here. The wetting angle θ defines a maximum radius of curvature τ _\ and a minimum radius of curvature r _{2 of} a meniscus 230 to be moved through the channel 220, where £ ι = r ₂ applies for the same height and width of the channel. 5c shows the situation when the air bubble or the meniscus 230 reaches the change in cross section 222 at the end of the channel 220.

If such a channel represents the area of a fluid system where the greatest capillary force has to be overcome, the pressure required in this special case is

2 4 Δp = σ - = σ - G1.3 r d

This pressure barrier is not to be neglected in microperistaltic pumps of the type according to the invention due to the small geometry dimensions if such a channel represents the constriction of the pump. With a cable diameter of, for example, d = 50 μ and a surface span air / water of σ _wa = 0.075 N / m, the pressure barrier is Δp _b = 60 hPa, while with a duct diameter d = 25 μm the pressure barrier is Δp _b = 120 hPa.

In the case of microperistaltic pumps of the type according to the invention, however, the constriction mentioned is generally defined by the distance between the valve membrane and the opposite area of the pump body (for example a sealing lip) when the valve is open. This constriction represents a gap that has an infinitely wide width compared to the height, ie ri = r and r ₂ = infinite.

For such a channel, the following results from equation 2:

Δp = σ- G1.4 r

In general, the relationship between the smallest radius of curvature and the smallest wall distance d is given by the following relationship:

G1.5

2 • sin (90 ° + T - Θ)

where Θ represents the wetting angle and F the tilt between the two walls.

The worst-case scenario, ie the smallest radius of curvature regardless of the tilt angle and wetting angle, is given when the sine function becomes maximum, ie sin (90 ° 4 -Θ) = 1. This occurs for example at the abrupt cross-sectional changes such as, o- in FIGS. 5a to 5c are shown with the combination of tilting angle T and Benet ^¬ wetting angle Θ on. In the worst case scenario:

r = - G1.6

2 The smallest occurring radius of curvature can therefore be considered as independent of the tilt angle T, wetting angle Θ or abrupt changes in cross-section, half of the smallest emerging wall distance.

In a peristaltic pump, on the one hand, there are fluid connections between the chambers with a given channel geometry and a constriction that defines the smallest flow dimension d. The following applies to such a channel:

4 Δp = σ - Eq. 7. d

On the other hand, the peristaltic pump has a constriction at the inlet or outlet valve, which is defined by the gap geometry dependent on the valve stroke d. The following applies to these:

2 Δp = σ— G1.8. d

The respective constriction (channel constriction or valve constriction in the open state) at which larger capillary forces have to be overcome can be regarded as the flow constriction of the microperistaltic pump.

In preferred exemplary embodiments of the present invention, connecting channels within the peristaltic pump are therefore designed in such a way that the diameter of the channel exceeds at least twice the valve constriction, ie the distance between the membrane and the pump body when the valve is open. In such a case, the valve gap represents the flow constriction of the microperistaltic pump. For example, with a valve stroke of 20 μm, connecting channels with a smallest dimension, ie constriction, of 50 μm can be provided. The upper limit of the channel diameter is determined by the dead volume of the channel. The capillary force to be overcome depends on the surface tension at the liquid / gas interface. This surface tension in turn depends on the partners involved. For a water / air interface, the surface tension is approximately 0.075 N / m and varies slightly with temperature. Organic solvents generally have a significantly lower surface tension, while the surface tension at a mercury / air interface is, for example, approximately 0.475 N / m. A peristaltic pump, which is designed to overcome the capillary force at a surface tension of 0.1 N / m, is therefore suitable for pumping almost all known liquids and gases in a bubble-tolerant and self-priming manner. Alternatively, the compression ratio of a micro-peristaltic pump according to the invention can be made correspondingly higher in order to enable such a pumping, for example also for mercury.

The design rules discussed in the following apply to the conveyance of gases and incompressible liquids, whereby when conveying liquids it must be assumed that air bubbles fill the entire pump chamber volume in the worst-case scenario. When pumping gases, it must be expected that liquid can get into the pump due to condensation. In the following it is assumed that the piezo actuator is designed in such a way that all required negative and positive pressures can be achieved.

First, consider a pressure stroke. During the ejection process, the actuator membrane compresses the gas volume or air volume. The maximum overpressure in the pump chamber po is then determined by the pressure in the air bubble. It is calculated from the state equation of the air bubble.

The variables p ₀ , V ₀ , ΔV and p _ü were explained above with reference to FIG. 4. γ _A represents the adiabatic coefficient of the gas, that is, the air. The left side of the above equation represents the state before compression, while the right side represents the state after compression. Furthermore, the overpressure po during the pressure stroke must be greater than the positive delivery pressure p _F :

po> P _F Eq. 10

Now consider a suction stroke. The suction stroke differs in the initial position of the volumes. After the expansion, the negative pressure p _ö arises in the pump chamber, ie p ₀ is negative:

Po * = (Po + PuXVo + ΔV) ^ΪA Eq.ll

The left side of equation 11 represents the state before expansion, while the right side represents the state after expansion. The vacuum p ₀ during the pressure stroke must be less than the necessary negative delivery pressure p _F. It should be noted that the delivery pressure p _{F is} positive in terms of amount when considering the pressure stroke, and is negative in amount when considering the suction stroke. It follows:

Pu <p _F G1.12

For the minimum necessary compression ratio of bubble-tolerant microperistaltic pumps for the pressure stroke, the following equations result:

The following compression ratio results for the suction stroke:

If the delivery pressure p _{F is} small compared to the atmospheric pressure Po, the previous equations can be simplified as follows, which corresponds to a linearization around the point p ₀ , V ₀ :

Pressure stroke: ε> - ^ I Eq. 15

YA Po

Suction stroke: ε> - G1.16

YA PO

The valid equation for the suction stroke and the pressure stroke is:

YA PO

In the case of rapid changes in state, the conditions are adiabatic, ie γ _a = 1.4 for air. In the case of slow changes in state, the conditions are isothermal, ie γ _A = 1. With a consistent application of the worst case assumption, the criterion with γ _A = 1 is used below. Thus, as a design rule for the necessary compression ratio of bubble-tolerant microperistaltic pumps, it can be stated that the compression ratio must be greater than the ratio of the delivery pressure to the atmospheric pressure, ie:

ε> ^ G1.18

po

Or with the volumes mentioned: ^> M G1.19

V ₀ Po

The simple linear design rule given above corresponds to the tangent to the isothermal equation of FIG. 4 at point p ₀ , V ₀ .

Preferred embodiments of the invention microperistaltic are thus designed such that the compression ratio satisfies the above condition, the minimum necessary discharge pressure in Equation 8 corresponds to DEFINE ^¬ th pressure when having minimum dimensions in the peristaltic pump occurring Kanalengstellen at least twice as large as the valve gap are. Alternatively, the minimum required delivery pressure can correspond to the pressure defined in equation 3 or equation 7 if the flow restriction of the microperistaltic pump is not defined by a gap but by a channel.

If a microperistaltic pump according to the invention is to be used when pressure boundary conditions of a negative pressure pi at the inlet or a counter pressure p ₂ at the outlet prevail, the compression ratio of a microperistaltic pump must be correspondingly larger in order to enable pumping against these inlet pressures or outlet pressures. The pressure boundary conditions are defined by the intended application of the microperistaltic pump and can range from a few hPa to several 1000 hPa. For such cases, the overpressure po or underpressure Po occurring in the pumping chamber must at least reach these counter pressures so that a pumping effect occurs. For example, only the Höhendif ^¬ leads ferenz a possible inlet vessel and the discharge vessel of 50 cm in water at back pressures of 50 hPa.

Furthermore, the desired delivery rate represents a boundary condition that places additional requirements. For a given stroke volume ΔV, the delivery rate Q is determined by the operating frequency f of the repeating peristaltic cycle. It defines: Q = ΔV "f. Both the suction stroke and the pressure stroke of the peristaltic pump must be performed within the period T = 1 / f, in particular the stroke volume ΔV must be implemented. The available time is therefore a maximum of T / 2 for suction stroke and The time required to convey the stroke volume through the pump chamber feed line and the valve constriction now depends on the one hand on the flow resistance and on the other hand on the pressure amplitude in the pump chamber.

If foam-like substances are to be pumped with a microperistaltic pump according to the invention, it may be necessary to overcome a plurality of capillary forces, as described above, since several corresponding liquid / gas interfaces occur. In such a case, the microperistaltic pump must be designed to have a compression ratio in order to be able to generate ^{correspondingly} higher delivery pressures.

In summary, it can be stated that the compression ratio of a microperistaltic pump according to the invention must be chosen to be correspondingly higher if the delivery pressure p _F necessary in the microperistaltic pump also depends on the boundary conditions of the application in addition to the capillary forces mentioned. It should be noted that here the delivery pressure is considered relative to the atmospheric pressure, ie a positive delivery pressure p _{F is} assumed in the pressure stroke, while a negative delivery pressure p _{F is} assumed in the suction stroke. An amount of the delivery pressure of at least p _F = 100 hPa can therefore be assumed as a technically sensible value for robust operation for a suction stroke and a pressure stroke.

If one considers a back pressure of, for example, 3000 hPa at the pump outlet, against which it is necessary to pump, then a compression ratio of ε> 3 results according to equation 13 above, an atmospheric pressure of 1013 hPa being assumed. If the microperistaltic pump has to suction against a large negative pressure, for example a negative pressure of -900 hPa, then a compression ratio of ε> 9 must be maintained according to equation 14 above in order to enable pumping against such a negative pressure.

Examples of peristaltic micropumps that enable the realization of such compression ratios are explained in more detail below.

6b shows a schematic cross-sectional view of a peristaltic micropump with membrane element 300 and pump body 302 along the line bb of FIGS. 6a and 6c, while FIG. 6a shows a schematic plan view of the membrane element 300 and FIG. 6c shows a schematic plan view of the pump body 302 shows. The membrane element 300 in turn has three membrane sections 12, 14 and 16, which are each provided with piezo actuators 22, 24 and 26. In turn, an inlet opening 32 and an outlet opening 34 are formed in the pump body 302, such that the inlet opening 32 together with the membrane region 12 defines an inlet valve, while the outlet opening 34 with the membrane region 16 defines an outlet valve. A pump chamber 304 is formed in the pump body 302 below the membrane section 14. Furthermore, fluid channels 306 are formed in the pump body 302, which are fluidly connected to the valve chambers 308 and 310 assigned to the membrane regions 12 and 16. The valve chambers 308 and 310 are in the shown embodiment by recesses in the Membranele ^¬ element 300 formed, forms 312 ge ^¬ in the membrane element 300 also a contributing to the pumping chamber 304 is recess.

In the embodiment shown in FIGS. 6a to 6c, the pump chamber volume 304 is made larger than the volume of the valve chambers 308 and 310. This is achieved in the embodiment shown by a pump chamber lowering in which a structuring in the form of a pumping chamber lowering is formed in the pump body 302. The stroke of the pump membrane 14 is preferably designed so that it can largely displace the volume of the pump chamber 304.

A further increase in the pump chamber volume compared to the valve chamber volume is achieved in the exemplary embodiment shown in FIGS. 6a to 6c in that the pump chamber membrane 14 is made larger in area (in the plane of the membrane element 300 or the pump body 302) than the valve chamber membranes, as best seen in Figure 6a. This results in a pump chamber that is larger in area compared to the valve chambers.

In order to reduce the flow resistance between the valve chambers 308 and 310 and the pump chamber 304, the supply channels 306 are structured in the surface of the pump body 302. These fluid channels 306 provide a reduced flow resistance without significantly deteriorating the compression ratio of the peristaltic micropump.

As an alternative to the exemplary embodiment shown in FIGS. 6a to 6c, the surface of the pump body 302 could be implemented with three-stage depressions in order to implement the pump chamber of increased depth (compared to the valve chambers), while the upper chip is an essentially unstructured membrane , Such two-stage reductions are technologically somewhat more difficult to implement than the exemplary embodiment shown in FIGS. 6a to 6c.

Exemplary dimensions of the embodiment of a peristaltic micropump shown in FIGS. 6a to 6c are as follows:

Dimension of the valve membrane 12, 16: 7.3 x 5.6 mm; Dimension of the pump membrane 14: 7.3 x 7.3 mm; Membrane thickness: 40 μm;

Diameter of the inlet and outlet nozzle 32, 34: at least 50 μm;

Valve chamber height: 8 μm; Pump chamber height: 30 μm;

Width of the valve sealing lips d _DL : lOμm; realizable overall size: 8 x 21 mm;

Dimensions of the piezo elements: area: 0.8 times the membrane dimension, thickness: 2.5 times the membrane thickness; Piezo element thickness: 100 μm; and

Opening cross section of the openings 32, 34: 100 μm x 100 μm.

An enlarged view of the left part of the cross-sectional view shown in FIG. 6b is shown in FIG. 7, the height H of the pumping chamber 304 being shown in FIG. 7. Although the structures in the pump body 302 and in the membrane element 300 forming the pump chamber 304 have the same depths as shown in FIG. 7, it is preferred to structure the structures in the pump body 302 with a greater depth than that in the membrane element in order to achieve this To provide flow channel 306 with a sufficient flow cross-section, but without unduly affecting the compression ratio. For example, the structures in the pump body 302 that contribute to the fluid channel 306 and the pump chamber 304 can have a depth of 22 μm, while the structures in the membrane element 300 that define the valve chambers 308 or contribute to the pressure chamber 304 have a depth of 8 μm.

FIG. 8 is a schematic cross-sectional view of an enlargement of section A of FIG. 7, but in a modified form. According to FIG. 8, the web is spaced from the opening 32 in the direction of the channel 206. This allows assembly tolerances to be taken into account in double-sided lithography. Furthermore, it can be prevented that wafer thickness fluctuations, the valve openings with different cross-sectional sizes Can have consequences, have no negative effects. As can be seen in FIG. 8, the distance x to the membrane 12 defines the flow constriction between the pump chamber and the valve passage opening when the valve position is open.

As stated above, in the areas of the fluid system in which a pumping action is required by forming a pump chamber volume of a peristaltic pump, the compression ratio of the peristaltic pump must be chosen large in order to ensure self-filling behavior and robust operation with regard to a bladder tolerance to ensure. To achieve this, it is preferred to keep the dead volume small, which can be supported by adapting the contour or shape of the pump chamber to the bending line of the pump membrane in the deflected state.

A first way to implement such an adaptation is to implement a round pumping chamber, i.e. a pump chamber, the circumferential shape of which is adapted to the deflection of the pump membrane. A schematic top view of the pump chamber and fluid channel section of a pump body with such a pump chamber is shown in FIG. 9a. The fluid channels 306, which produce a fluid connection to valve chambers, which in turn can be structured in a membrane element, for example, flow into the round pump chamber 330, comparable to the illustration in FIG. 6c.

In order to be able to achieve a further reduction in the dead volume and thus a further increase in the compression ratio, the pumping chamber under the pumping membrane can be designed such that its contour facing the pumping membrane follows the bending line of the pumping membrane with a precise fit. Such a contour of the pump chamber can be achieved, for example, by an appropriately shaped injection molding tool or by an embossing stamp. A schematic plan view of a pump body 340 in which such a fluid chamber 342 structures the bending line of the actuator membrane is shown in Fig. 9b. Furthermore, fluid channels 344 structured in the pump body are shown in FIG. 9b, which lead to and away from the fluid chamber 342. A schematic cross-sectional view along the line cc of FIG. 9b is shown in FIG. 9c, a diaphragm 346 with the piezo actuator 348 associated therewith also being shown in FIG. 9c. Flow through the fluid channels 344 is indicated by arrows 350 in FIG. 9c. Furthermore, FIG. 9c shows the contour 352 of the fluid chamber or pump chamber 342, which is facing the membrane 346 and is adapted to the bending line of the membrane (in the actuated state). This shape of the fluid chamber 352 enables the entire volume of the fluid chamber 342 to be displaced when the diaphragm 346 is actuated by the piezo actuator 348, as a result of which a high compression ratio can be achieved.

An embodiment of a peristaltic micropump, in which both the pump chamber 342 and valve chambers 360 are adapted to the bending lines of the respectively assigned membrane sections 12, 14 and 16, is shown in FIGS. 10a and 10b, with FIG. 10b a schematic top view points to the pump body 340, while FIG. 10a shows a schematic cross-sectional view along the line aa of FIG. 10b. As is apparent from FIGS. 10a and 10b, shape and contour are 360 and 362 as explained above with reference to the pumping chamber 342 of the valve chamber, adapted to the Bie ^¬ gelinie of the associated diaphragm portion 12 and 16 respectively. As further best seen in FIG. 10b, fluid channels 344a, 344b, 344c and 344d are again formed in the pump body 340. Fluid channel 344a represents an input fluid channel, fluid channel 344b connects valve chamber 360 to pump chamber 342, fluid channel 344 connects pump chamber 342 to valve chamber 362, and fluid channel 344d represents an outlet channel.

As further shown in FIG. 10 a, the diaphragm element 380 in this exemplary embodiment is an unstructured diaphragm element which is provided in a pump body 340. see recess is introduced in order to define the valve chambers and the pump chamber together with the fluid regions formed in the pump body 340.

The connecting channels 344b and 344c between the chambers Aktorkam ^¬ are connected so that they contain a low compared to the stroke volume of dead volume. At the same time, these fluid channels significantly reduce the flow resistance between the actuator chambers, so that larger pumping frequencies and thus larger delivery flows are also possible, such a flow being again indicated by arrows 350 in FIG. 10a. In the area of the valve chambers 360 and 362, the fluid channels are separated by actuating the membrane sections 12 and 16, respectively, through the fully deflected membrane sections, so that fluid separation occurs between the fluid channels 344a and 344b or between the fluid channels 344c and 344d. The contour of the valve chambers must be adapted exactly to the bending line of the respective membrane sections in order to achieve a tight fluid separation. Alternatively, as shown in FIG. 11, a web 390 can be provided in the respective valve chamber in the region of the largest stroke of the membrane section 12, which is shaped accordingly so that it can be completely sealed by the bending of the membrane section 12. More particularly, the web to the edges of the valve chamber ^¬ bends upward, according to the adjusted at the bend line form the valve chamber. This web can protrude into the respective valve chamber, alternatively, as shown in FIG. 11, the depth of the connecting channels 344 can be greater than the stroke y of the diaphragm section 12, at which the diaphragm section lies against the pump body, so that the web 390 is sunk, so to speak. If the depth of the connecting channels is greater than the maximum stroke, this comes at the expense of the compression ratio, but enables low flow resistances between the actuator chambers. An alternative exemplary embodiment of a valve chamber 360 is shown in FIG. 12, where the depth of the connecting channels 344 is smaller than the maximum stroke y of the membrane section 12, and thus as the depth of the valve chamber 360 adapted to the bending line of the membrane section 12 in the region of the largest Stroke of the diaphragm section 12. This enables a secure seal to be achieved when the valve is closed.

In order to achieve a valve seal in the closed state, which meets the specified pressure requirements, it can be preferred to provide a web 390a in the valve chamber 360 which does not meet the maximum possible bending line of the actuator element, i. H. of the membrane section 12 together with the piezo actuator 22, as shown in FIG. 13. The maximum possible bending line of the membrane section 12 is shown in FIG. 13 by a dashed line 400, while the line 410 corresponds to the maximum possible deflection of the membrane section 12 due to the provision of the web 390a. Thus, in the fully deflected state, when the web 390 is sealed, the membrane 12 rests on the web 390a with a residual force, which residual force can be dimensioned in order to meet pressure requirements which the seal has to withstand.

In practical implementations, the bending line of the membrane will often not be perfectly concentric with the center of the membrane, for example due to assembly tolerances of the piezoceramics and due to inhomogeneities in the adhesive application by which the piezoceramics are attached to the membranes. The area of the web seal can therefore be increased somewhat, for example by approximately 5 to 20 μm, depending on the stroke of the actuator, compared to the rest of the fluid chamber, in order to ensure reliable contact of the membrane with the web and thus a secure seal. This also corresponds to the situation shown in FIG. 13. It should be noted, however, that this increases the dead volume and reduces the compression ratio. As an alternative to the options mentioned, a plastically deformable material, for example silicone, can be used as the fluid chamber material, at least in the area under the movable membrane. Inhomogeneities can then be compensated for by appropriately large actuator forces. In such a case, there is no longer a hard-hard seal, so that there is a certain tolerance against particles and deposits.

An exemplary dimensioning of a peristaltic pump as shown in FIGS. 10a and 10b is briefly given below. The thickness of the membrane sections 12, 14 and 16 and thus the thickness of the membrane element 380 can be 40 μm, for example, while the thickness of the piezo actuators can be 100 μm, for example. A PZT ceramic with a large d31 coefficient can be used as the piezoceramic. The side length of the membranes can be, for example, 10 mm, while the side length of the piezo actuators can be, for example, 8 mm. The voltage swing for actuating the actuators in the aforementioned actuator geometry can be, for example, 140 V, which results in a maximum stroke of approximately 100 to 200 μm with a stroke volume of the pump membrane of approximately 2 to 4 μl.

By adjusting the fluid chamber execution to the bending of the membrane ^¬ line, the dead volume of the three required for the peristaltic pump fluid chambers falls away, so that only the connecting channels, the chambers, the valve chamber with the pumping connect remain. If connecting channels with a depth of 100 μm, a width of 100 μm and a length of 10 mm each, so that the overall length for the fluid channels 344b and 344c is 20 mm, this results in a pump chamber dead volume of 0.2 μl. From this, a compression ratio ε = ΔV / V = 4 μl / 0.2 μl = 20 can be determined. With such a large compression ratio of up to 20, such fluid modules are bubble-tolerant and self-priming and can convey both liquids and gases. Such fluid pumps can also build up in principle several bar pressure for compressible and liquid media, depending on the design of the piezo actuator. In such a micropump, the maximum pressure that can be generated is no longer limited by the compression ratio, but rather by the maximum force of the drive element and the tightness of the valves. Despite these properties, a suitable channel dimensioning with a low flow resistance can deliver several ml / min.

In the exemplary embodiment described above, all of the fluid channels, i. H. the inlet fluid channel 344a and the outlet fluid channel 344d are also guided laterally, i. H. the fluid channels run in the same plane as the fluid chambers. As stated above, the sealing of the channels can be difficult with such a course. An advantage of the lateral course of the fluid channels, however, is that the entire fluid system, including reservoirs connected to the inlet channel 344a and / or the outlet channel 344d, can be molded in one manufacturing step, for example by injection molding or embossing.

FIG. 14 shows an exemplary embodiment of a microperistaltic pump according to the invention, in which the inlet fluid channel 412 and the outlet fluid channel 414 are sunk vertically in the pump body 340. The fluid channels 412 and 414 have 412a and 414a at a substantially vertical portion, each substantially centrally in the Ventilkam ^¬ numbers under the parent to ^¬ diaphragm portions 12 and 16, 360 and 362 open. The advantage of the exemplary embodiment of the fluid channels shown in FIG. 14 is that the fluid channels can be sealed in a defined manner. However, a disadvantage is that such vertically recessed Flu ^¬ idkanäle production technique difficult to manufacture. The peristaltic micropumps according to the invention are preferably controlled in that the membrane, for example the metal membrane or the semiconductor membrane, is at a ground potential, while the piezoceramics are moved by a typical peristaltic cycle, in each case by applying corresponding voltages to the piezoceramics.

In addition to the microperistaltic pump described above using three fluid chambers 342, 360 and 362, a peristaltic micropump according to the invention can have further fluid chambers, for example another fluid chamber 420, which is connected to the pump chamber 342 via a fluid channel 422. Such a structure is shown schematically in FIG. 15, wherein a first reservoir 424 is connected to the valve chamber 360 via the fluid channel 344a, a second reservoir 426 is connected to the valve chamber 420 via a fluid channel 428 and a third reservoir 430 via the Fluid channel 344d is connected to the valve chamber 362.

A structure with four fluid chambers _/. 15, for example, can form a branching structure or a mixer in which the mixed streams can be actively promoted. The expansion to four fluid chambers with four assigned fluid actuators enables, as shown for example in FIG. 15, the implementation of three peristaltic pumps, wherein each pump direction between all reservoirs 424, 426 and 430 can be implemented in both directions. It is possible for a single membrane element to cover all fluid chambers and reservoir containers, a separate piezo actuator being provided for each fluid chamber. The entire fluid system can thus be made very flat, the functional, fluid structures including fluid chambers, channels, membranes, piezo actuators and support structures having a total height of the order of 200 to 400 μm. Thus, systems conceivable that can be integrated into chip cards. Furthermore, flexible fluidic systems are even conceivable.

In addition to the exemplary embodiments shown, fluid chambers can be connected in any way on one level. For example, different reservoirs. B. each be assigned a microperistaltic which feed then at ^¬ game as reagents to a chemical reaction (for example, a fuel cell) or Ka ^¬ libriersequenz carry out for an analysis system, wherein ^¬ play, in a water analysis i

To produce a piezo membrane transducer, the piezoceramics can be glued to the respective membrane sections, for example. Alternatively, the piezoceramics, for example PZT, can be applied directly using thick-film technology, for example by screen printing with suitable intermediate layers.

An alternative embodiment of an inventive pump with recessed ^¬ SEN mikroperistaltischen Einlaßfluid- channel 412 and recessed Auslaßfluidkanal 414 is shown in Fig. 16. In turn, the Einlaßflußkanal 412 opens into the we ^¬ sentlichen centrally below the diaphragm portion 12 in a valve chamber 442, while the Auslaßfluidkanal 414 in ^¬ we sentlichen centrally below the diaphragm portion 16 in a valve chamber 444 opens. The respective orifices of the inlet channel 412 and the outlet channel 414 are provided with ei ^¬ ner sealing lip 450th Furthermore, a pump chamber 452 is formed in the pump body 440, which is fluidly connected to the valve chambers 442 and 444 by fluid channels in walls 454. According to the in Fig. Embodiment shown 16, the three diaphragm portions 12, 14 and 16, in turn, a membrane element 456. In this embodiment, the diaphragm sections are however laktoren by Piezostape- driven 460, 462 and 464, the sponding to the entspre ^¬ diaphragm portions form placeable are. For this purpose, the piezo stack actuators are used using suitable ones Housing parts 470 and 472, which are shown in Fig. 16 remote from the pump body and the membrane element, are used.

Piezo stack actuators are advantageous in that the same do not have to be fixedly connected to the membrane element, so that the same modular construction ermögli ^¬ chen. In the case of such piezo stack actuators which are not firmly connected, the actuators do not actively retract a membrane section when actuation thereof is ended. Rather, the membrane section can only be moved back by the restoring force of the elastic membrane itself.

The peristaltic micropumps according to the invention can be manufactured using a wide variety of manufacturing materials and manufacturing techniques. The pump body can be made of silicon, for example, made of plastic by injection molding, or machined using precision engineering. The Membranele- ment that forms the drive diaphragm for the two valves and the pumping chamber can be made of silicon, by a metal foil such as stainless steel or titanium may be formed, by an in Zweikomponen ^¬ ten-injection molding manufactured with conductive coating virtue provided plastic membrane can be formed, or can be realized by an elastomer membrane.

The connection of the diaphragm element and the pump body is an important point because high shear forces can occur at this connection during the operation of the peristaltic pump. The following requirements apply to this connection:

thick; thin joint layer (<10 μm) because the pump chamber height is a critical one affected; mechanical resistance; and chemically resistant to media to be pumped. In the case of silicon as the basic structure and membrane element, silicon fusion bonding without a joining layer can be carried out. In the case of a silicon-glass combination, anodic bonding can preferably be used. Other options are eutectic wafer bonding or wafer bonding.

If the basic structure is made of plastic and the membrane element is a metal foil, lamination can be carried out if an adhesion promoter is used between the membrane element and the basic structure. Alternatively, gluing with an adhesive with high shear strength can take place, in which case capillary stop trenches are then preferably formed in the basic structure in order to prevent glue from penetrating into the fluid structure.

If both the membrane element and the pump body are made of plastic, ultrasonic welding can be used to connect them. If one of the two structures is optically transparent, laser welding can alternatively take place. In the case of an elastomeric membrane, the sealing properties of the membrane can be further used to make a seal by clamping to be granted ^¬.

The following explains briefly how a possible buildin ^¬ account the membrane can be made to the pump body in an inventive microperistaltic. If the diaphragm is glued to the pump body in the micropump according to the invention, it should be noted that the metering of joining layer materials (eg adhesive) is critical, since on the one hand the diaphragm must be completely sealed (that is, sufficient adhesive must be applied) and on the other hand penetration of excess adhesive into the fluid chambers must be avoided.

The bonding layer material may be an adhesive or an adhesive ^¬ medium is, for example, by dispensing or by applied an appropriately shaped stamp to the joint layer. After the application of the joining layer material, the membrane is placed on the base body. Possible burrs, which can be, for example, at the edge of the membrane when separated, are accommodated in a corresponding receptacle for the burr, so that a defined position of the membrane is ensured, above all in the direction perpendicular to the surface thereof, with regard to dead volume and tightness important is.

Then a stamp is pressed onto the pump body so that the adhesive layer remains as thin and defined as possible. In order to absorb excess adhesive, a capillary stop trench can be provided, which surrounds the fluid areas formed in the pump body. Thus, such excess adhesive cannot get into the fluid chambers. Under these conditions, the adhesive can be defined and harden thinly. Curing can take place at room temperature or accelerated in the oven or by UV radiation when using UV-curing adhesives.

As an alternative to the adhesive technique described, the base body or pump body can be loosened as a connection technique by means of suitable solvents and a plastic membrane can be joined to the base body.

Claims

claims

1. Peristaltic micropump with the following features:

a first membrane area (12) with a first piezo actuator (22; 460) for actuating the first membrane area;

a second membrane area (14) with a second piezo actuator (24; 462) for actuating the second membrane area;

a third membrane area (16) with a third piezo actuator (26; 464) for actuating the third membrane area; and

a pump body (30; 302; 340; 440),

which, together with the first membrane area (12), forms a first valve (62), the passage opening (32) of which is open when the first membrane area is not actuated and the passage opening can be closed by actuating the first membrane area,

which, together with the second membrane region (14), forms a pump chamber (42; 304; 330; 342; 452), the volume of which can be reduced by actuating the second membrane region, and

which, together with the third membrane area (16), forms a second valve (64), the passage opening (34) of which is open when the third membrane area is not actuated, and the passage opening of which can be closed by actuating the third membrane area,

wherein the first and second valves (62, 64) are fluidly connected to the pump chamber.

2. The peristaltic micropump according to claim 1, in which the following relationship applies between a stroke volume ΔV, a dead volume V ₀ , a delivery pressure P _F and the atmospheric pressure P ₀ :

ΔV / Vo> P _F / P ₀ ,

wherein the displacement .DELTA.V is the displaced upon actuation of the second diaphragm portion (14) volume, wherein the dead volume V ₀ is a volume that is between the open passage opening (32; 34) of the valves (62, 64) and the closed passage opening ( 32, 34) of the other of the valves (62, 64) is in the actuated state of the second membrane region (14), and the delivery pressure p _{F is} the pressure required in the pumping chamber (42; 304; 330; 342; 452) to move a liquid / gas interface past a flow restriction in the peristaltic micropump.

3. A peristaltic micropump according to claim 1 or 2, in which a first valve chamber (308; 360; 442) is formed between the first membrane region (12) and the pump body (302; 340; 440) and in which between the third membrane region (16 ) and the pump body (302; 340; 440), a second valve chamber (310; 362; 444) is formed, the valve chambers being fluidly connected to the pump chamber (42; 304; 330; 342; 452).

4. The peristaltic micropump according to claim 3, wherein the volume of the pump chamber (304) is greater than the volume of the first or the second valve chamber (308, 310).

5. A peristaltic micropump according to claim 4, in which a distance between the membrane surface and the pump body surface is greater in the region of the pump chamber (304) than in the region of the valve chamber (308, 310).

6. Peristaltic micropump according to claim 4 or 5, in which the second membrane area (14) and the pumping chamber are larger in area than the first or third membrane area (12, 16) and the associated valve chambers.

7. Peristaltic micropump according to one of claims 3 to 6, in which the membrane regions (12, 14, 16) are formed in a membrane element (10; 300; 380; 456), the valve chamber (308, 310; 360, 362; 442, 444), the pump chamber (42; 304; 330; 342; 452) and fluid channels (306; 344) between the valve chambers and the pump chamber are formed by structuring in the pump body and / or in the membrane element.

8. Peristaltic micropump according to one of claims 1 to 7, wherein the pumping chamber (330; 342) has a structure in the pump body (340), the contour of the structure being adapted to the curved contour of the second diaphragm section (14) in the actuated state is.

9. Peristaltic micropump according to one of claims 3 to 7, in which the pump chamber (342) and the valve chambers (360, 362) structuring in the pump body

(340), the contours of the structuring being adapted to the respective curved contour of the corresponding membrane section (12, 14, 16) in the actuated state.

10. A peristaltic micropump according to any one of claims 1 to 9, wherein the first and third membrane areas

(12, 16) and the piezo actuators (22, 26; 460, 464) are designed in such a way that, when actuated, they press a counter element (390; 390a) with a predetermined force in order to close the respective valve ,

11. The peristaltic micropump according to claim 9, which has lateral fluid supply lines (344a, 344d) to the valve chambers (360, 362) which are formed in the pump body (340) and which are closed by actuating the corresponding membrane section.

12. A peristaltic micropump according to claim 11, in which a web (390; 390a) is provided in the region of a valve chamber (360, 362) against which the corresponding actuated membrane section abuts in order to close the corresponding lateral fluid line.

13. A peristaltic micropump according to claim 11, in which the valve chambers opposite the respective membrane section have a plastically deformable material against which the respective membrane section abuts in the actuated state.

14. A peristaltic micropump according to one of claims 1 to 13, which further has at least one further membrane region with a further piezo actuator for actuating the further membrane region, the further membrane region together with the pump body forming a further valve, the passage opening of which in the unactuated state further membrane region is open and the passage opening can be closed by actuating the further membrane region, the further valve is fluidly connected to ^'' of the pumping chamber.

15. Peristaltic micropump according to one of claims 1 to 14, in which the piezo actuators are piezo membrane transducers, which are formed by respective piezo elements applied to a membrane area.

16. Peristaltic micropump according to claim 15, in which the piezo elements on the respective membrane area glued or formed in thick-film technology on the respective membrane area.

17. Peristaltic micropump according to one of claims 1 to 14, in which the piezo actuators are formed by respective piezo stacks.

18. Fluid system with a plurality of peristaltic micropumps according to one of claims 1 to 17 and a plurality of reservoirs which are fluidly connected to the peristaltic micropumps.