Optimizing electroosmotic pumping rates in a rectangular channel with inserted baffle plates

• Main Authors: Anison K. R. Lai, 賴冠叡
• Other Authors: Chien-Cheng Chang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/55qmks

博士 === 國立臺灣大學 === 應用力學研究所 === 106 === The Helmholtz-Smoluchowski (H-S) velocity is known to be an accurate and useful formula for estimating the electro-osmotic (EO) flow rates in a simple micro-channel with a thin electric-double layer. However, in case the channel cross section is not so simple, the usefulness of H-S velocity could be sharply limited. A fundamental interest representing this situation would be a rectangular channel with built-in baffle plates or flow channel with groove walls, where baffle plates may develop a different normalized zeta potential α on the surface other than those on channel walls β. In this study, semi-analytical solutions are pursued under the Debye Hückel approximation (DHA) to obtain EO pumping rates of the three different channel structures. First is EO flow in a rectangular channel with vertical baffle plates, abbreviated as vertical plate (VP) problem; second would be EO flow in a rectangular channel with horizontal baffle plates, abbreviated as horizontal plate (HP) problem; third is EO flow in a rectangular channel with groove walls, abbreviated as groove wall (GW) problem. The three distinguished problem are investigated in a case when EO flow is either driven along or transverse to the plates or grooves, thus distinguishing longitudinal EO pumping (LEOP) and transverse EO pumping (TEOP). In particular, we examine how the EO pumping rates deviate from those predicted by the H-S velocity, and a diagram of optimal EO pumping rates on the α−β plane in introduced that accounts for the general features of the analysis.