Aging Effects on Oxidized and Amine-Modified Poly(dimethylsiloxane) Surfaces Studied with Chemical Force Titrations: Effects on Electroosmotic Flow Rate in Microfluidic Channels

Abstract

Poly(dimethylsiloxane) (PDMS) has been used extensively as a substrate material for microfluidic devices because of its low cost and the ease with which micron-sized features can be molded. PDMS, however, has disadvantages compared to other materials including high hydrophobicity and minimal surface charge. Surface modification by Telsa coil oxidation can be utilized to augment these properties by yielding a hydrophilic surface that is capable of possessing a significant zeta potential at high pH's. However, the modification is only temporary because the hydrophilic surface begins to revert back to its original hydrophobic form, exhibiting a 75% decrease in flow associated with the surface modification in less than 24 h. We show that derivatizing the PDMS surface with (aminopropyl)triethoxysilane following oxidation yields a surface that is more hydrophilic than the native material. Using a combination of chemical force microscopy (CFM) and electroosmotic measurements, we show that this surface is still m...