Surfaces, including microfluidic channels, with controlled wetting properties
The present invention generally relates to coating materials, including photoactive coating materials. In some aspects of the invention, a sol-gel is provided that can be formed as a coating on a microfluidic channel. One or more portions of the sol-gel can be reacted to alter its hydrophobicity, in some cases. For instance, in one set of embodiments, a portion of the sol-gel may be exposed to light, such as ultraviolet light, which can be used to induce a chemical reaction in the sol-gel that alters its hydrophobicity. In one set of embodiments, the sol-gel can include a photoinitiator, that upon exposure to light, produces radicals. Optionally, the photoinitiator may be conjugated to a silane or other material within the sol-gel. The radicals so produced may be used to cause a polymerization reaction to occur on the surface of the sol-gel, thus altering the hydrophobicity of the surface. In some cases, various portions may be reacted or left unreacted, e.g., by controlling exposure to light (for instance, using a mask). Such treated surfaces within a microfluidic channel may be useful in a wide variety of applications, for instance, in the creation of emulsions such as multiple emulsions.
1. An article, comprising:
a sol-gel coating comprising a photoinitiator coated on at least a portion of a microfluidic channel,
wherein a first portion of the sol-gel coating is relatively hydrophobic, and a second portion of the sol-gel coating is relatively hydrophilic.
2. The article of claim 1 , wherein the microfluidic channel is defined within a microfluidic device comprising polydimethylsiloxane.
3. The article of claim 1 , wherein the microfluidic channel is defined within a microfluidic device comprising glass.
4. The article of claim 1 , wherein the coating comprises a silane.
5. The article of claim 1 , wherein the coating comprises a fluorosilane.
6. The article of claim 1 , wherein the coating comprises a moiety comprising a thiol.
7. The article of claim 1 , wherein the photoinitiator is Irgacure 2959.
8. The article of claim 1 , wherein the sol-gel coating has a thickness of no more than about 10 micrometers.
9. The article of claim 1 , wherein at least a portion of the sol-gel coating comprises acrylic acid.
10. A method, comprising:
exposing at least a portion of a microfluidic channel to a sol;
causing at least a portion of the sol to gel within the microfluidic channel to form a sol-gel coating comprising a photoinitiator; and
altering the hydrophobicity of a first portion of the sol-gel coating without altering the hydrophobicity of a second portion of the sol-gel coating.
11. The method of claim 10 , wherein causing at least a portion of the sol to gel comprises heating the sol.
12. The method of claim 10 , wherein causing at least a portion of the sol to gel within the microfluidic channel to form a sol-gel coating comprises leaving the sol undisturbed for a time of at least about an hour.
13. The method of claim 10 , wherein causing at least a portion of the sol to gel comprises vaporizing the solvent within the sol.
14. The method of claim 10 , wherein altering the hydrophobicity of the first portion of the sol-gel coating comprises exposing the first portion to a solution comprising a monomer.
15. The method of claim 14 , further comprising causing at least a portion of the monomer to polymerize to the sol-gel coating, thereby altering the hydrophobicity of the first portion of the sol-gel coating.
16. The method of claim 10 , wherein altering the hydrophobicity of the first portion of the sol-gel coating comprises exposing at least a portion of the sol-gel to ultraviolet light.
17. The method of claim 10 , further comprising reacting at least a portion of the microfluidic channel to produce silanols.
18. The method of claim 17 , wherein reacting at least a portion of the microfluidic channel to produce silanols comprises exposing at least a portion of the microfluidic channel to an oxygen plasma.
19. The method of claim 10 , wherein the sol is pretreated by treating the sol in the absence of the microfluidic channel such that some condensation within the sol occurs.
20. The method of claim 19 , wherein the sol is pretreated by heating the sol.
21. The article of claim 1 , wherein the coating comprises heptadecafluorooctylsilane.
22. The article of claim 1 , wherein the coating comprises heptadecafluorosilane.
23. An article, comprising:
a sol-gel coating at least a portion of which comprises acrylic acid coated on at least a portion of a microfluidic channel,
wherein a first portion of the sol-gel coating is relatively hydrophobic, and a second portion of the sol-gel coating is relatively hydrophilic.
24. The article of claim 23 , wherein the microfluidic channel is defined within a microfluidic device comprising polydimethylsiloxane.
25. The article of claim 23 , wherein the microfluidic channel is defined within a microfluidic device comprising glass.
26. The article of claim 23 , wherein the coating comprises a silane.
27. The article of claim 23 , wherein the coating comprises a fluorosilane.
28. The article of claim 23 , wherein the coating comprises a moiety comprising a thiol.
29. The article of claim 23 , wherein the sol-gel coating has a thickness of no more than about 10 micrometers.
30. The article of claim 23 , wherein the coating comprises heptadecafluorooctylsilane.
31. The article of claim 23 , wherein the coating comprises heptadecafluorosilane.
32. The article of claim 23 , wherein the acrylic acid is chemically bonded to the sol-gel coating.
33. The article of claim 23 , wherein the portion of the sol-gel coating comprising acrylic acid is less hydrophobic than a portion of the sol-gel coating free of acrylic acid.