US20080025853A1

US20080025853A1 - Micro Impedance Pump For Fluid Logic, Mixing and Separation

Info

Publication number: US20080025853A1
Application number: US11/775,791
Authority: US
Inventors: Morteza Gharib; Derek Rinderknecht
Original assignee: California Institute of Technology CalTech
Current assignee: California Institute of Technology CalTech
Priority date: 2006-07-10
Filing date: 2007-07-10
Publication date: 2008-01-31

Abstract

An impedance pump system formed on a rigid substrate is substantially planar, in a plane defined by a substrate. A micro machined opening is made in the substrate, and an impedance pump, formed by a lumen which can be a tubular elastic device having two different fluidic impedances with a wave reflection site therebetween, is formed within the opening. An actuator is formed to pump using the device.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Applications 60/819,871, filed Jul. 10, 2006 and 60/842,758, filed Sep. 7, 2006. The disclosure of the prior applications are considered part of (and are incorporated by reference in) the disclosure of this application.

BACKGROUND

A valveless microimpedance pump is described in U.S. Pat. No. 7,163,385. This pump enables pumping fluid using fluidic differences between conduit types, and pumps without using one way valves or the like.

SUMMARY

An embodiment describes a modular plug and play micropump which can be used to drive and control microfluidic systems.
An embodiment is planar in format and modular.
An embodiment uses rigid materials, and a planar format for microfluidic applications.
An embodiment uses rigid and/or flexible micro impedance pumps formed by masking and depositing metals, micromachining and/or etching.
An embodiment uses both flexible and rigid materials.
An embodiment uses an embedded actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a pump device on a modular chip; and
FIG. 2 shows a pump device which has two actuators.

DETAILED DESCRIPTION

An embodiment uses an impedance pump of the type disclosed in U.S. Pat. No. 7,163,385, the disclosure of which are here with incorporated by reference.
According to an embodiment, a modular plug-and-play type micropump is used within a microfluidic system. The device is planar and can be integrated into different kinds of technologies including Web on-chip technology or the like. The channels can have characteristic dimensions, for example, on the order of a micron. Therefore, this can easily be integrated into current lab-on-chip technologies. Integration of a compact pump into current microfluidic systems creates the potential for true lab on chip devices where not only the channels have characteristic dimensions on the order of a micron but also the components on which they operate.
The impedance pump is formed as shown in FIG. 1. A substrate 199 can be a semiconductor substrate, e.g., a semiconductor chip, or micromachined substrate or circuit board. All of the parts described herein are formed on that substrate.
A flexible lumen 100 includes a first part 105 with a first fluidic characteristic and a second part 110 with a second fluidic characteristic. The lumen extends along an axis of the substrate. The lumen 100 is asymmetrically excited by an excitation part 120, which can be a pincher that constricts at least a part of the outer cross section of the lumen, to form a pressure wave. First part 105 of the lumen 100 has a different fluidic characteristic than second part 110 of the lumen. For example, the different fluidic characteristic between the two parts can be compliance, geometry, or any other physical property which creates a site for wave reflection. Moreover, there can be multiple different parts, in addition to the two parts shown in FIG. 1.
The wave reflection sites, comprised of a mismatch in impedance at the interface of different materials 108 and/or by a change in geometry, is excited asymmetrically with respect to the fluidic system to drive flow.
The actuator 120 is controlled by a controller 125 which can operate according to a prestored procedure. The controller 125 can carry out excitation over a specific range of frequencies to create constructive wave interactions based on reflections from the reflection area 108. The constructive wave interaction creates a pressure gradient to drive the flow. In an embodiment, the contoller seeks resonance or other optimum characteristics in the constructive wave interference.
The controller can alternatively be off chip, in which case, an input line is substituted for the controller 125.
Other fluidic parts shown generically as 130 can also be added, which can include diffusers, valves and other such flow rectifiers. These can increase performance as desirable. The other fluidic parts 130 can be passive or car also be controlled by the controller 125.
In the embodiment, the impedance pump is planar, with all of the structure on the same plane defining a plane of the substrate. The lumen may be tubular, for example, and the actuator 120 may be pinchers either surrounding the lumen, or on positions on the plane defined by the substrate.
An embodiment uses rigid materials for many parts of the lumen, so that both flexible and rigid materials can both be used. The materials, formed of rigid and/or flexible micro impedance pumps formed by masking and depositing metals, micromachining and/or etching.
Actuator 120 can be formed of a deposited active thin-film such as piezoelectrics, magnetostrictive or ferroelectrics. Other deposited films can include structure for actuating electrostatically, magnetically, pneumatically, hydraulically or any other actuation method. If the excitation device 120 is a piezoelectric device, it can work by uni-morph or bi-morph.
In a first embodiment, the piezoelectric element can be in contact with the outside of the walls. A second embodiment in FIG. 2 embeds the piezoelectric element 205 within at least one of the walls capable of transmitting an excitation.
These structures can be created using soft lithography to fabricate them monolithically making them low cost, disposable and easily added to current lab-on-chip designs.
In an embodiment, the walls themselves can be formed of polymeric materials such as silicone, polyisoprene, polyimide, polyurethane or parylene. Alternatively, the walls can be made of rigid materials such as silicon, glass, or metallic materials such as nickel, titanium, or iron based metals such as stainless steel. The walls of the lumen may be formed inside openings that are micromachined in the substrate 100.
A first embodiment describes monolithically forming the layers. Alternatively, the unit may be built in a series of layers as in FIG. 2, where one or more of the layers 200 may function as the excitation transmitting wall. The excitation transmitting wall 200 should be at least partly deformable so allow transmitting the excitation. The outer wall can be deformable, or can be rigid, e.g., metallic. The layers can be formed by means of a micromolding process such as spinning down a photo resist, exposure, and development, patterning of the pump material and forming the device on a separate substrate. A different micromolding process can alternatively be used, such as spinning down a photo resist, exposure, and development, patterning of the pump material and subsequent removal of the resist through access ports. An alternative micromolding process may use imprint lithography.
This device makes possible the use of other such medical devices are also possible due to the new packaging. It can be used in flexible nature of the micropump such as active coronary bypass stents and blood flow assist devices. Such a modular micropump can also easily be micromachined or etched into stiffer materials such as metals or silicon to be structurally rigid for high pressure operation. At least one wall of the lumen, should be deformable to allow actuation.
Multiple pumps can be added in series or in parallel allowing for a vast range of flow outputs as well as complex patterns for fluidic logic. Many configurations are therefore possible with minimal connections to the chip. The ability to have many modules allows precise sample volumes to be delivered in a controlled manner.
The pump operates in pulses. The pulsatile nature of the flow provides enhanced mixing of reactants on a microscale due to the extremely high transient oscillatory fluid velocities. In addition, the reversible nature of the micropump further enhances on-chip control. A modular micro impedance based pumping system therefore has vast potential for application such as cell sorting, as well as chemical mixing and analysis for high throughput drug screening.
In a first embodiment, the device can have a closed flexible cavity connected at either end to create closed channels of different compliance, geometry or any other physical property which creates a site for wave reflection along which an excitation or compression occurs located asymmetrically with respect to the fluid system.
In another embodiment, the lumen 100 can be open at both ends, defining a fluid input 99, and a fluid outlet 101.
Another embodiment may use multiple pumps are used in a single layer or multiple layers to enable operation in series or parallel to enhance performance.
The FIG. 2 embodiment uses two separate actuators, e.g., two or more piezoelectric elements 205, 210, placed in contact with the same wall or more than one wall such as opposing walls capable of transmitting an excitation. These actuators, in this embodiment, may be as disclosed above, with all the features disclosed above, e.g., the elements may be uni-morph or bi-morph, in contact with or embedded within at least one of the walls capable of transmitting an excitation.
According to an aspect, the micropump can completely close the main cavity and therefore function as a valve.
The general structure and techniques, and more specific embodiments which can be used to effect different ways of carrying out the more general goals are described herein.
Although only a few embodiments have been disclosed in detail above, other embodiments are possible and the inventor (s) intend these to be encompassed within this specification. The specification describes specific examples to accomplish a more general goal that may be accomplished in another way. This disclosure is intended to be exemplary, and the claims are intended to cover any modification or alternative which might be predictable to a person having ordinary skill in the art. For example, different materials can be used.
Also, the inventor(s) intend that only those claims which use the words “means for” are intended to be interpreted under 35 USC 112, sixth paragraph. Moreover, no limitations from the specification are intended to be read into any claims, unless those limitations are expressly included in the claims. The computers described herein may be any kind of computer, either general purpose, or some specific purpose computer such as a workstation. The computer may be an Intel (e.g., Pentium or Core 2 duo) or AML) based computer, running Windows XP or Linux, or may be a Macintosh computer. The computer may also be a handheld computer, such as a PDA, cellphone, or laptop.
The programs may be written in C or Python, or Java, Brew or any other programming language. The programs may be resident on a storage medium, e.g., magnetic or optical, e.g. the computer hard drive, a removable disk or media such as a memory stick or SD media, wired or wireless network based or Bluetooth based Network Attached Storage (NAS), or other removable medium or other removable medium. The programs may also be run over a network, for example, with a server or other machine sending signals to the local machine, which allows the local machine to carry out the operations described herein.
Where a specific numerical value is mentioned herein, it should be considered that the value may be increased or decreased by 20%, while still staying within the teachings of the present application, unless some different range is specifically mentioned. However, the tubing may be any size that is appropriate for micromaching. For example the lumens described herein can be tubing having a diameter of anything between 500 nm and 5 mm, typically 1 um or 5 um.
Where a specified logical sense is used, the opposite logical sense is also intended to be encompassed.

Claims

1. A pumping system, comprising:

a substrate, formed of a material that can be micromachined;

at least one lumen opening formed in said substrate, said lumen opening being substantially extending along an axis of the substrate, said lumen opening including at least a first portion having a first fluidic characteristic, and a second portion having at least a second fluidic characteristic, and a wave reflection interface between said first and second portions;

an actuator, formed adjacent said lumen opening in said substrate, and formed to actuate in an area of the lumen opening to pump fluid within the lumen opening; and

a controller connection to said actuator, also formed in said substrate, operative to allow control of said actuator.

2. A system as in claim 1, further comprising a tubular material in said lumen opening.

3. A system as in claim 1, wherein said lumen opening comprises an opening which is etched in the substrate material, and further comprising at least one deformable material within the etched substrate material.

4. A system as in claim 3, further comprising a second material, in said lumen opening, the first and second materials collectively forming a multilayer lumen.

5. A system as in claim 4, wherein said second material is a rigid material.

6. A system as in claim 4, wherein said actuator is formed between said first and second materials.

7. A system as in claim 3, wherein said actuator is formed outside of said deformable material.

8. A system as in claim 1, further comprising a second actuator.

9. A system as in claim 1, further comprising a controller, coupled to said controller connection, which operates to excite said lumen in a way that creates constructive wave interactions based on reflections from said wave reflection interface.

10. A system as in claim 1, wherein said actuator is a deposited thin film.

11. A system as in claim 1, wherein said walls are formed of a rigid material.

12. A system as in claim 1, wherein said walls are formed by micro-molding.

13. A method comprising:

Micromachining at least one lumen opening formed in a substrate to extend along an axis of the substrate, said micromachining forming an opening including at least a first portion having a first fluidic characteristic, and a second portion having at least a second fluidic characteristic, and a wave reflection interface between said first and second portions;

Forming an actuator adjacent said lumen opening in said substrate in a location to actuate in an area of the lumen opening and to pump fluid within the lumen opening; and

Controlling the actuator in a way to form constructive wave reflection at said wave reflection interface and to pump fluid.

14. A method as in claim 13, further comprising depositing a tubular material in said lumen opening.

15. A method as in claim 14, wherein said tubular material includes at least one deformable material within the etched substrate material.

16. A method as in claim 15, further comprising depositing a second material in said lumen opening, the first and second materials collectively forming a multilayer lumen material.

17. A method as in claim 16, wherein said second material is a rigid material.

18. A method as in claim 16, wherein said actuator is formed between said first and second materials.

19. A method as in claim 15, wherein said actuator is formed outside of said deformable material.

20. A method as in claim 1, further comprising using a second actuator in addition to said actuator, to pump fluids.

21. A method as in claim 13, wherein said actuator includes a deposited thin film.

22. A pumping system, comprising:

at least one lumen, formed of a first layer that is substantially rigid, and a second layer, inside said first layer, that is flexible, said lumen having at least a first portion having a first fluidic characteristic and a second portion having at least a second fluidic characteristic with at wave reflection interface between said first and second portions;

an actuator, formed adjacent said flexible portion of said lumen to actuate in an area of the lumen in a way that allows pumping of fluid within the lumen; and

23. A system as in claim 22, wherein said lumen is tubular in shape.

24. A system as in claim 22, wherein said actuator is formed between said first and second layers.