Improving the Electrokinetic Properties of PDMS With Surface Treatments

Abstract

PDMS (Polydimethylsiloxane) is widely used as a microfluidic chip material for various applications due to its desirable properties [1, 2]. However PDMS has several drawbacks that limit its utilization in a number of microfluidic applications [1–4]. Properties such as the hydrophobic nature, sample absorption, and low electrokinetic properties (low zeta potential) are some issues that must be considered before using PDMS for numerous applications [3]. In many PDMS based chips electroosmotic pumping is used for fluid flow and sample transport along the microchannel networks. Simplicity of implementation in microfluidic chips, fast response time, and the plug-like velocity profile are the major advantages of electroosmotic flow compared to other fluid pumping techniques [2]. This type of flow utilizes the formation of electric double layer (EDL) in microchannels and the movement of ions under an applied external electric field. Thus, the surface properties of the channel material and liquid properties (ionic concentration, pH, and viscosity) play major roles in electroosmotic pumping for different solutions in microchannels.