Modification of poly(dimethylsiloxane) microfluidic channels with silica nanoparticles based on layer-by-layer...

Area of Science:

• Microfluidics
• Surface Chemistry
• Analytical Chemistry

Background:

• Poly(dimethylsiloxane) (PDMS) is a common material for microfluidic devices.
• Native PDMS surfaces are hydrophobic, limiting their use in aqueous electrokinetic applications.
• Achieving stable and controllable electroosmotic flow (EOF) in PDMS microchips is crucial for efficient separations.

Purpose of the Study:

• To develop a simple and reproducible method for creating a hydrophilic PDMS microchip.
• To enhance the electroosmotic flow (EOF) stability and reproducibility in PDMS microchannels.
• To evaluate the performance of the modified PDMS chip for electrophoretic separations.

Main Methods:

• Coating PDMS microchannels with poly(diallyldimethylammonium chloride) (PDDA) and silica nanoparticles.
• Characterization using contact angle measurements and charge-coupled device (CCD) imaging.
• EOF measurements and electrophoretic separation of dopamine and epinephrine.

Main Results:

• The modified PDMS surface became hydrophilic, with a water contact angle decreasing from 113° to 64°.
• EOF values on the coated PDMS chip were comparable to glass chips above pH 7.0.
• The coated PDMS chip exhibited excellent stability and reproducibility (RSD of 0.57% for EOF).
• High-resolution separation of dopamine and epinephrine was achieved, with theoretical plates up to 1.40 x 10^5 /m.

Conclusions:

• A simple silica nanoparticle coating effectively renders PDMS hydrophilic and stable.
• The modified PDMS microchip provides stable and reproducible EOF, suitable for high-performance separations.
• This method offers a cost-effective approach to improve PDMS-based microfluidic devices for analytical applications.