Rotating electroosmotic flows in soft parallel plate microchannels

Abstract

We present a theoretical investigation of rotating electroosmotic flows (EOFs) in soft parallel plate microchannels. The soft microchannel, also called as the polyelectrolyte-grafted microchannel, is denoted as a rigid microchannel coated with a polyelectrolyte layer (PEL) on its surface. We compare the velocity in a soft microchannel with that in a rigid one for different rotating frequencies and find that the PEL has a trend to lower the velocities in both directions for a larger equivalent electrical double layer (EDL) thickness λFCL (λFCL = 0.3) and a smaller rotating frequency ω (ω < 5). However, for a larger rotating frequency ω (ω < 5), the main stream velocity u far away from the channel walls in a soft microchannel exceeds that in a rigid one. Inspired by the above results, we can control the EOF velocity in micro rotating systems by imparting PELs on the microchannel walls, which may be an interesting application in biomedical separation and chemical reaction.