Microfluidic large scale integration

• US 20050072946A1
• Filed: 08/10/2004
• Published: 04/07/2005
• Est. Priority Date: 09/25/2002
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Anderson, W. French, Quake, Stephen R., Maerkl, Sebastian J., Studer, Vincent
• Granted Patent: US 8,220,494 B2
• Time in Patent Office: Days
• US Class Current: 251/11
• CPC Class Codes: F15C 1/06 Constructional details; Selection of specified materials ; Constructional realisation of one single element; Canal shapes; Jet nozzles; Assembling an element with other devices, only if the element forms the main part F15C5/00 takes precedence
• CPC Class Codes: G06F 2111/10 Numerical modelling
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]
• CPC Class Codes: Y10T 137/2224 Structure of body of device

Abstract

Using basic physical arguments, a design and method for the fabrication of microfluidic valves using multilayer soft lithography is presented. Embodiments of valves in accordance with the present invention feature elastomer membrane portions of substantially constant thickness, allowing the membranes to experience similar resistance to an applied pressure across their entire width. Such on-off valves fabricated with upwardly- or downwardly-deflectable membranes can have extremely low actuation pressures, and can be used to implement active functions such as pumps and mixers in integrated microfluidic chips. Valve performance was characterized by measuring both the actuation pressure and flow resistance over a wide range of design parameters, and comparing them to both finite element simulations and alternative valve geometries.

Claims

1. A microfluidic device comprising:

a first layer including a first recess in a first surface;

an elastomeric second layer having a first side in contact with the first surface to define a first microfluidic channel, a membrane portion of the second layer adjacent to the first microfluidic channel exhibiting a substantially constant thickness; and

a third layer in contact with a second side of the elastomeric second layer to define a second microfluidic channel, the membrane portion deflectable into one of the first and second microfluidic channels in response to pressure within the other of the first and second microfluidic channels.

2. The microfluidic device of claim 1 wherein the second microfluidic channel is defined between the third layer and a second recess in a second side of the second layer, such that the membrane portion is upwardly deflectable into the first microfluidic channel in response to pressure applied to the second microfluidic channel.

3. The microfluidic device of claim 2 wherein the second microfluidic channel exhibits a rectangular cross-section.

4. The microfluidic device of claim 1 wherein the second microfluidic channel is defined between the second layer and a second recess in the third layer, such that the membrane portion is downwardly deflectable into the second microfluidic channel in response to pressure applied to the first microfluidic channel.

5. The microfluidic device of claim 4 wherein the second microfluidic channel exhibits a curved cross-section.

6. The microfluidic device of claim 5 wherein the third layer comprises a rigid substrate.

7. The microfluidic device of claim 6 wherein the substrate comprises glass.

8. The microfluidic device of claim 7 wherein the second recess comprises an etched recess.

9. The microfluidic device of claim 1 wherein the third layer comprises a polymer.

10. The microfluidic device of claim 9 wherein the second layer comprises PDMS.

11. The microfluidic device of claim 1 wherein the microfluidic flow channel exhibits a depth:

width aspect ratio of between about 1;

5 and 1;

1.

12. The microfluidic device of claim 1 wherein the microfluidic flow channel exhibits a width of 100 μ

m or less.

13. The microfluidic device of claim 1 wherein a width of the microfluidic control channel is greater than a width of the microfluidic flow channel.

14. The microfluidic device of claim 1 further comprising an actuation fluid within the microfluidic control channel.

15. A method of controlling flow in a microfluidic structure, the method comprising:

providing a microfluidic control channel separated from an adjacent microfluidic flow channel by an elastomer membrane having a substantially constant thickness; and

applying pressure to the control channel such that the elastomer membrane is deflected into the microfluidic flow channel.

16. The method of claim 15 wherein pressure is applied to the microfluidic control channel filled with water.

17. The method of claim 15 wherein application of the pressure deflects the membrane upward into the overlying microfluidic flow channel.

18. The method of claim 15 wherein application of the pressure deflects the membrane downward into the underlying microfluidic flow channel.

19. A method of fabricating a microfluidic structure, the method comprising:

molding a first elastomer material over a first raised feature exhibiting a rounded cross-section to define a flow recess in a first side of the first elastomer material;

molding a second elastomer material over a second raised feature exhibiting a rectangular cross-section to define a control recess in a first side of the second elastomer material;

placing the first side of the second elastomer material against a planar substrate; and

placing the first side of the first elastomer material against a second side of the second elastomer material such that the flow recess is separated from the control channel by an elastomer membrane having substantially constant thickness.

20. The method of claim 19 further comprising forming the first raised feature by patterning photoresist over a first workpiece.

21. The method of claim 20 further comprising heating the first workpiece to reflow the photoresist to form the rounded cross-sectional profile.

22. A method of fabricating a microfluidic structure, the method comprising:

providing a substrate having a concave recess in an upper surface;

placing a first side of a first elastomer layer having substantially constant thickness into contact with the upper surface to define a microfluidic flow channel;

molding a second elastomer material over a first raised feature to define a control recess in a first side of the second elastomer material; and

placing the first side of the second elastomer material against a second side of the first elastomer layer to define a microfluidic control channel separated from the microfluidic control channel by an elastomer membrane of substantially constant thickness.

23. The method of claim 22 wherein providing the substrate comprises providing a glass substrate having the concave recess etched therein.

24. The method of claim 22 wherein providing the substrate comprises providing a polymer substrate embossed to form the concave recess.

25. The method of claim 22 wherein providing the substrate comprises:

molding a third elastomer material over a raised feature exhibiting a rounded cross-section; and

removing the third elastomer material from the raised feature.

26. The method of claim 25 further comprising forming the first raised feature by patterning photoresist over a first workpiece.

27. The method of claim 26 further comprising heating the first workpiece to reflow the photoresist to form the rounded cross-sectional profile.