Microfluidic devices with flexible optically transparent electrodes

1. A microfluidic integrated optoelectronic tweezers (OET) apparatus, comprising:

an upper polydimethylsiloxane (PDMS) chamber with an embedded single-walled nanotube (SWNT) thin film electrode; and

a lower photoconductive OET surface, the photoconductive OET providing a lower electrode.

2. An apparatus according to claim 1 , wherein the lower electrode comprises:

an indium tin oxide (ITO) layer;

a 50-nm heavily doped n-F hydrogenated amorphous silicon (n+a-Si:H) layer over the ITO layer;

a photoconductive 1-μm undoped hydrogenated amorphous silicon (a-Si:H) layer over the n+a-Si:H layer; and

a 100-nm silicon dioxide layer over the undoped a-Si:H layer.

3. An apparatus according to claim 2 , wherein the silicon dioxide layer facilitates bonding with PDMS.

4. An apparatus according to claim 1 :

wherein the PDMS chamber comprises a PDMS channel;

wherein the channel has a top surface; and

wherein the SWNT embedded PDMS thin film electrode is fabricated on the top surface of the PDMS channel.

5. An apparatus according to claim 2 :

wherein for operating this device, an alternating current (AC) bias is applied to the embedded SWNT thin film electrode and the lower OET photoconductive electrode;

wherein when light beams illuminate the a-Si:H layer, virtual electrodes are turned on to create non-uniform electric field between the lower light-patterned virtual electrode and embedded SWNT thin film electrode for dielectrophoresis (DEP) manipulation; and

wherein when a virtual electrode is turned on by a projected light beam, cells or particles experiencing DEP forces are moved away or attracted to the light pattern.

6. The apparatus of claim 1 , further comprising:

an upper control PDMS channel, wherein at least a portion of the upper control PDMS channel is located above a region where at least a portion of the upper PDMS chamber is located.

7. A method for fabricating a polydimethylsiloxane (PDMS) microfluidic channel with an embedded single-walled nanotube (SWNT) thin film electrode, comprising:

preparing a SWNT solution;

collecting an SWNT network from the solution with an anodic aluminum oxide (AAO) filter;

preparing a PDMS stamp as a mold for a microfluidic chamber, the PDMS stamp having an upper mold surface;

contacting the AAO filter with the upper mold surface of the stamp, wherein the SWNT network is transferred onto the upper mold surface;

spin coating a thin layer of PDMS over the SWNT network;

forming a thicker layer of PDMS over the thin layer, wherein the thin and thicker layers bond after curing and form a molded structure with a PDMS microfluidic channel; and

removing the molded structure from the mold;

wherein the SWNT network is transferred and embedded into the PDMS microfluidic channel.

8. An electrokinetic microfluidic device, comprising:

a first wall comprising a flexible mesh transparent electrode;

a second wall; and

a chamber between said first wall and said second wall, said chamber configured to hold a liquid;

wherein an electric field can be created in said chamber by placing a biasing voltage source between said transparent electrode and said second wall, said electric field providing an electrokinetic mechanism for moving said liquid or a particle in said liquid in said chamber.

9. The device of claim 8 :

wherein said chamber is partially defined by a flexible material disposed on said second wall; and

wherein said transparent electrode is flexible and embedded in said flexible material.

10. The device of claim 9 , wherein said flexible material partially defining said chamber is sufficiently flexible to allow said chamber to be pinched closed.

11. The device of claim 10 :

wherein said transparent electrode is sufficiently flexible to flex with said flexible material as said chamber is pinched closed; and

wherein said transparent electrode remains electrically conductive as said chamber is pinched closed.

12. The device of claim 9 :

wherein said second wall comprises a photoconductive layer disposed on a conductive layer; and

wherein said biasing voltage source can be connected to said conductive layer.

13. The device of claim 9 , wherein said flexible material comprises a polydimethylsiloxane (PDMS) material.

14. The device of claim 13 , wherein said second wall further comprises an outer material that facilitates bonding with said PDMS material.

15. The device of claim 9 , wherein said transparent electrode is a thin film electrode.

16. The device of claim 9 , wherein said transparent electrode comprises nanoparticles.

17. The device of claim 16 , wherein said nanoparticles comprise nanotubes or nanowires.

18. The device of claim 8 , wherein said second wall comprises a photoconductive layer responsive to light passed through said transparent electrode to create virtual electrodes that induce dielectrophoresis (DEP) forces sufficient to move a particle in said liquid.

19. The device of claim 8 , wherein said second wall comprises:

a photoconductive layer; and

an optoelectronic wetting surface that is an inner surface of said chamber.

20. The device of claim 19 , wherein said photoconductive layer of said second wall is responsive to light passed through said transparent electrode to create virtual electrodes that induce dielectrophoresis (DEP) forces that move a droplet of said liquid in said chamber.

21. The device of claim 8 , wherein said second wall comprises an array of fixed electrodes each selectively connectable to said biasing voltage source.

22. The device of claim 21 , wherein said second wall further comprises an insulating material covering said fixed electrodes.

23. The device of claim 8 , wherein said transparent electrode is a thin film electrode.

24. The device of claim 8 , wherein said transparent electrode comprises nanoparticles.

25. The device of claim 24 , wherein said nanoparticles comprise nanotubes or nanowires.

26. The device of claim 8 , wherein said transparent electrode comprises clusters of nanoparticles.

27. The device of claim 8 , wherein said transparent electrode comprises nanoparticles embedded in a flexible material.

28. The device of claim 27 , wherein said flexible material is a polymer or a silicone.

29. The device of claim 8 , wherein said transparent electrode comprises a combination of nanowires and nanoparticles embedded in a flexible material.

30. The device of claim 8 further comprising a biasing voltage source between said transparent electrode and said second wall.

31. The device of claim 9 , wherein said transparent electrode comprises clusters of nanoparticles.

32. The device of claim 9 , wherein said transparent electrode comprises nanoparticles embedded in a flexible material.

33. The device of claim 32 , wherein said flexible material is a polymer or a silicone.

34. The device of claim 9 , wherein said transparent electrode comprises a combination of nanowires and nanoparticles embedded in a flexible material.