Microfluidic large scale integration
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.
1. A microfluidic device comprising:
a first layer comprising a first side and including a first recess in said first side, said first recess comprising a curved surface;
a monolithic elastomeric second layer having a first side and a second side and including a second recess in said second side,
wherein the first side of the second layer is in contact with the first side of the first layer, and the first side of the second layer and the first recess define a first microfluidic channel with a transverse cross-section that comprises a curved upper surface running lengthwise along the channel, thereby forming an arched profile,
a third layer comprising a planar surface, wherein the planar surface is in contact with the second side of the elastomeric second layer and, the planar surface and the second recess define a second microfluidic channel with a transverse cross-section that comprises a curved upper surface running lengthwise along the channel, thereby forming an arched profile, the second fluidic channel crossing under the first microfluidic channel,
wherein the first microfluidic channel and second microfluidic channels are separated by a membrane portion of the second layer, wherein the membrane portion of the second layer is:
deflectable into the first microfluidic channel in response to pressure within the second microfluidic channel and
deflectable into the second microfluidic channel in response to pressure within the first microfluidic channel.
2. The microfluidic device of claim 1 wherein the third layer comprises a rigid substrate.
3. The microfluidic device of claim 2 wherein the substrate comprises glass.
4. The microfluidic device of claim 1 wherein the third layer comprises a polymer.
5. The microfluidic device of claim 4 wherein the second layer comprises polydimethylsiloxane (PDMS).
6. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width:depth aspect ratio of between about 1:1 and 50:1.
7. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width of 100 μm or less.
8. The microfluidic device of claim 1 wherein the width of the second microfluidic channel is greater than a width of the first microfluidic channel.
9. The microfluidic device of claim 1 further comprising an actuation fluid within the second microfluidic channel.
10. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width:depth aspect ratio of between about 2:1 and 20:1.
11. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width:depth aspect ratio of between about 3:1 and 15:1.
12. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width ranging from 0.2 to 500 μm.
13. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width ranging from 1 to 250 μm.
14. The microfluidic device of claim 1 wherein the one of the first or second microfluidic channels exhibits a width ranging from 10 to 200 μm.
15. The method of claim 1 , wherein the deflectable membrane is an elastomer with a Young's modulus of 50 Pa to 10 MPa.
16. The method of claim 1 , wherein the deflectable membrane is an elastomer with a Young's modulus of about 1 MPa.