Functionalized glass coating for PDMS microfluidic devices
Soft Matter Keywords
Microfluidic devices can perform multiple laboratory functions on a single, compact, and fully integrated chip. However, fabrication of microfluidic devices is difficult, and current methods, such as glass-etching or soft-lithography in PDMS, are either expensive or yield devices with poor chemical robustness. We introduce a simple method that combines the simple fabrication of PDMS with superior robustness and control of glass. We coat PDMS channels with a functionalized glass layer. The glass coating greatly increases the chemical robustness of the PDMS devices. As a demonstration, we produce emulsions in coated channels using organic solvents. The glass coating also enables surface properties to be spatially controlled. As a demonstration of this control, we spatially pattern the wettability of coated PDMS channels and use the devices to produce double emulsions with fluorocarbon oil.
The authors here demonstrate a method to to treat PDMS microfluidic devices with photoreactive glass coatings with the ability to spatially control wetability.
To make the chemically resistant glass coating the authors:
- mix equal volumes of:
- Tetraethoxysilane (TEOS) (Sigma)
- Methyltriethoxysilane (MTES) (Sigma)
- Hydrochloric acid aqueous pH 2
- Ethanol (Sigma)
- Flow mixture into PDMS device that has been recently bonded via plasma treating
- Heat at 100C for 10s, flush with air then heat while continually flushing with air.
Photoreactive sol-gel coating
- Mix photoiniator silane using:
- Irgacure 2959 photoinitiator (Ciba)
- Hydroquinone (Sigma)
- Dibutyltin dilaurate (Sigma)
- Dry chloroform (Sigma)
- 3-(triethoxysily)propyl isocyanate (Sigma)
- Use photoiniator to make sol-gel coating
- Dissolve 0.5g of photoiniator-silane in 2mL of
- Add 1mL Methyltriethoxysilane, 1mL Tetraethoxysilane, Trifluoroethanol and 0.5mL Heptadecafluoro-1,1,2,2- tetrahydrodecyl)triethoxysilane
- Add 1mL pH 2 HCL and mix at 200C
- Fill freshly bonded device (plasma) with sol-gel coating and wait for 2 min.
- Place on 220C hotplate to vaporize solvent and deposit coating onto channel walls.
Spatially pattern hydrophillic areas
- Mix hydrophillic monomer solution
- Add 0.2mL of acrylic acid to 0.8mL of 5mM NaIO4, 1mL ethanol and 0.05g benzophenone in 0.5mL acetone.
- Fill channels with monomer
- Illuminate desired areas with diaphragm of Kohler illuminated microscope
- Photopolymerize desired areas by exposing to UV light for 2-10 mins (time inversely proportional to channel size
- Flush with water