Surface Modification of PDMS for Control of Electroosmotic Flow: Characterization Using Atomic and Chemical Force Microscopy

Abstract

We describe the oxidation of the PDMS surface to form ionizable groups using a discharge from a Tesla coil and subsequent chemical modification to augment electroosmotic flow within polymeric microfluidic devices. The flow performance of oxidized, amine-modified and unmodified PDMS materials has been determined and compared to conventional glass devices. Results with different substrate materials correlates well with expected flow modifications as a result of surface modification. Oxidized PDMS devices were found to support faster electroosmotic flow (EOF) (twice that of native PDMS) similar to glass while those derivatized with APTES showed slower flow rates compared to native PDMS substrates as a result of masking surface charge. Chemical force microscopy has been utilized to monitor and measure the efficacy of surface modification yielding information about the acid/base properties of the modified and unmodified surfaces. Results demonstrate that the surface of PDMS micro-devices can be manipulated to control EOF characteristics using a facile surface derivatization methodology allowing surfaces to be tailored for specific microfluidic applications.