Single-sided light-actuated microfluidic device with integrated mesh ground
View Patent ↗Single-sided optoelectrowetting (SSOEW)-configured substrates are provided, as well as microfluidic devices that include such substrates. The substrates can include a planar electrode, a photoconductive (or photosensitive) layer, a dielectric layer (single-layer or composite), a mesh electrode, and a hydrophobic coating. Fluid droplets can be moved across the hydrophobic coating of such substrates in a light-actuated manner, upon the application of a suitable AC voltage potential across the substrate and the focusing of light into the photoconductive layer of the substrate in a location proximal to the droplets. Walls can be disposed upon the substrates to form the microfluidic devices. Together the walls and substrate can form a microfluidic circuit, through which droplets can be moved.
1. A substrate comprising:
a planar electrode;
a photoconductive layer;
a dielectric layer comprising at least a first layer of dielectric material;
a mesh ground electrode; and
a hydrophobic coating;
wherein the photoconductive layer is interposed between the planar electrode and the dielectric layer, with a bottom surface of the photoconductive layer adjoining a top surface of the planar electrode and a top surface of the photoconductive layer adjoining a bottom surface of the dielectric layer;
wherein the mesh ground electrode adjoins the dielectric layer, and wherein at least the first layer of dielectric material is interposed between the mesh ground electrode and the photoconductive layer;
wherein the planar electrode and the mesh ground electrode are configured to be connected to an AC voltage source; and
wherein, when the planar electrode and the mesh ground electrode are connected to opposing terminals of the AC voltage source, the substrate is capable of applying an opto-electrowetting (OEW) force to aqueous droplets in contact with the hydrophobic coating.
2. The substrate of claim 1 , wherein the substrate forms all or part of the base of a microfluidic device.
3. The substrate of claim 1 , wherein the photoconductive layer comprises hydrogenated amorphous silicon (a-Si:H).
4. The substrate of claim 1 , wherein the dielectric layer comprises a metal oxide.
5. The substrate of claim 4 , wherein the dielectric layer has a thickness of at least 125 nm and/or an impedance of about 10 kOhms to about 50 kOhms.
6. The substrate of claim 1 , wherein the dielectric layer further comprises a second layer of dielectric material, with a bottom surface of the first layer of dielectric material adjoining the photoconductive layer and a top surface of the first layer of dielectric material adjoining a bottom surface of the second layer of dielectric material.
7. The substrate of claim 6 , wherein the mesh ground electrode is interposed between the first layer of dielectric material and the second layer of dielectric material.
8. The substrate of claim 6 , wherein the first layer of dielectric material and the second layer of dielectric material both comprise a metal oxide.
9. The substrate of claim 6 , wherein the dielectric layer has a thickness of about 125 nm to about 175 nm and/or an impedance of about 10 kOhms to about 50 kOhms.
10. The substrate of claim 1 , wherein the mesh ground electrode comprises wires that are arranged in a lattice shape.
11. The substrate of claim 10 , wherein the mesh ground electrode comprises gold or aluminum.
12. The substrate of claim 10 , wherein the mesh ground electrode comprises aluminum that has an oxidized outer surface.
13. The substrate of claim 10 , wherein the mesh ground electrode has a linear fill factor β less than or equal to 10%.
14. The substrate of claim 13 , wherein wires of the mesh ground electrode have a pitch of about 200 microns to about 500 microns.
15. The substrate of claim 1 , wherein the hydrophobic coating has a bottom surface that adjoins at least a portion of a top surface of the dielectric layer, and optionally, wherein the bottom surface of the hydrophobic coating further adjoins a top surface of the mesh ground electrode.
16. The substrate of claim 15 , wherein the hydrophobic coating comprises an organofluorine polymer having at least one perfluorinated segment.
17. The substrate of claim 15 , wherein the hydrophobic coating comprises a densely packed monolayer of amphiphilic molecules covalently bonded to molecules of the dielectric layer.
18. The substrate of claim 17 , wherein the amphiphilic molecules of the monolayer each comprise:
a siloxane group, and wherein the siloxane groups are covalently bonded to the molecules of the dielectric layer;
a phosphonic acid group, and wherein the phosphonic acid groups are covalently bonded to the molecules of the dielectric layer; or
a thiol group, and wherein the thiol groups are covalently bonded to the molecules of the dielectric layer.
19. The substrate of claim 18 , wherein the amphiphilic molecules of the monolayer comprise long-chain hydrocarbons having a chain of at least 16 carbons.
20. The substrate of claim 18 , wherein the amphiphilic molecules of the monolayer comprise fluorinated carbon chains.
21. The substrate of claim 20 , wherein the fluorinated carbon chains have the chemical formula CF3-(CF2)m-(CH2)n-, wherein m is at least 2, n is at least 2, and m+n is at least 9.
22. The substrate of claim 18 , wherein the hydrophobic coating is patterned such that select regions are relatively hydrophilic compared to the remainder of the hydrophobic coating.
23. A microfluidic device comprising:
a base comprising the substrate of claim 1 ; and
walls disposed on a top surface of said base;
wherein the base and the walls together define a microfluidic circuit.
24. The microfluidic device of claim 23 further comprising a cover, wherein the cover is disposed on the walls.
25. The microfluidic device of claim 23 , wherein the microfluidic circuit comprises at least one microchannel and a plurality of chambers, wherein each chamber opens off of one microchannel of the at least one microchannel.
26. A method of moving a droplet in a microfluidic device of claim 23 , the method comprising:
disposing a droplet of an aqueous solution on a top surface of the base of the microfluidic device;
applying a AC voltage potential between the planar electrode and the mesh ground electrode;
directing structured light at a position on the top surface of the base, in a location proximal to the droplet; and
moving the structured light relative to the microfluidic device at a rate that induces the droplet to move across the top surface of the base.
27. The method of claim 26 , wherein the AC voltage potential is about 10 ppV to about 80 ppV.
28. The method of claim 27 , wherein the AC voltage potential has a frequency of about 1 kHz to about 1 MHz.
29. The method of claim 27 , wherein the AC voltage potential has a frequency of about 5 kHz to about 100 kHz.
30. The method of claim 27 , wherein the AC voltage potential is about 30 ppV to about 50 ppV.