Sodium hydroxide treatment of PDMS based microfluidic devices

Abstract

We discuss the use of aqueous NaOH as a facile surface treatment method to control the electroosmotic flow in PDMS microchannels. Flushing of PDMS/PDMS and glass/PDMS microchannels with 1 M NaOH for 24 h leads to a doubling of the electroosmotic flow. This high flow rate is comparable to the flow rates achieved by treating PDMS microchannels with O₂ plasma. Contact angle measurements and ATR-FTIR analysis show that the surface chemistry of the NaOH treated PDMS differs from O₂ plasma treated PDMS. An important advantage of the NaOH treated surfaces is the enhanced stability, irrespective of whether the devices are stored in air or water.