Sodium hydroxide treatment of PDMS based microfluidic devices

Area of Science:

• Materials Science
• Surface Chemistry
• Microfluidics

Background:

• Controlling electroosmotic flow (EOF) is crucial for microfluidic devices.
• Polydimethylsiloxane (PDMS) is a common material for microchannels, but its surface properties can change over time.
• Oxygen plasma treatment is a standard method to enhance EOF in PDMS.

Purpose of the Study:

• To investigate aqueous sodium hydroxide (NaOH) as a facile surface treatment for PDMS microchannels.
• To evaluate the impact of NaOH treatment on electroosmotic flow (EOF).
• To compare the stability and surface chemistry of NaOH-treated PDMS with oxygen plasma-treated PDMS.

Main Methods:

• PDMS/PDMS and glass/PDMS microchannels were treated with 1 M NaOH solution for 24 hours.
• Electroosmotic flow rates were measured.
• Contact angle measurements and Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) spectroscopy were used to analyze surface chemistry.
• Stability of treated surfaces was assessed after storage in air and water.

Main Results:

• NaOH treatment resulted in a doubling of the electroosmotic flow in PDMS microchannels.
• The achieved flow rates were comparable to those obtained with oxygen plasma treatment.
• Surface analysis revealed differences in surface chemistry between NaOH-treated and O2 plasma-treated PDMS.
• NaOH-treated surfaces exhibited enhanced stability when stored in air or water.

Conclusions:

• Aqueous NaOH is an effective and simple method for enhancing EOF in PDMS microchannels.
• NaOH treatment offers a stable alternative to oxygen plasma for modifying PDMS surface properties.
• The enhanced stability of NaOH-treated surfaces is advantageous for microfluidic device longevity.