Electroosmotic flow-switchable poly(dimethylsiloxane) microfluidic channel modified with cysteine based on gold...

Area of Science:

• Microfluidics
• Surface Chemistry
• Analytical Chemistry

Background:

• Poly(dimethylsiloxane) (PDMS) microfluidic channels are widely used but often require surface modifications for specific applications.
• Controlling electroosmotic flow (EOF) is crucial for efficient separations in microfluidic devices.
• Cysteine immobilization offers unique surface properties for chemical and biological applications.

Purpose of the Study:

• To develop an electroosmotic flow (EOF)-switchable microfluidic channel using poly(dimethylsiloxane) (PDMS) modified with cysteine.
• To investigate the reversibility and stability of the EOF switching behavior.
• To demonstrate the utility of the modified channel for separating small molecules.

Main Methods:

• Layer-by-layer assembly of poly(diallyldimethylammonium chloride) (PDDA) and gold nanoparticles on PDMS.
• Immobilization of cysteine onto the gold nanoparticle surface.
• Characterization using infrared spectroscopy/attenuated total reflection, contact angle measurements, and EOF measurements.
• Electrophoretic separation of analytes.

Main Results:

• Reversible switching of EOF direction (cathodic-anodic) was achieved by varying the pH of the running buffer.
• The modified channel surface demonstrated high reproducibility and good stability.
• Successful separation of dopamine/epinephrine and arginine/histidine was performed on the chip.
• EOF magnitude showed limited variation at pH > 6.0 or pH < 4.0.

Conclusions:

• The developed cysteine-modified PDMS microfluidic channel provides a robust platform for pH-controlled EOF switching.
• The channel exhibits stable and reproducible performance, suitable for microscale separations.
• This technology offers a versatile tool for manipulating fluid flow in microfluidic systems.