Transition of AC electroosmotic flow to chaos nearby electric double layer by frequency-dependent routes*

So far, most of the investigations on the velocity fluctuations of electroosmotic flow driven by periodic electric field (PEOF) are by theoretical and numerical analysis, which are based on conventional understanding, such as commonly used apparent viscosity, linear and 1D electric double layer (EDL) and linearized fluid dynamics. Although the influence of nonlinear and nonuniform electric field on electroosmotic flows has been developed for several years, due to the lack of experimental supports, our understanding of ACEO flows or even the most fundamental DC electroosmotic flows is far from complete. In present, based on the measurement using laser induced fluorescent photobleaching anemometer with ultrahigh spatial and temporal resolutions, the nonlinear velocity response of ACEO flow has been observed and experimentally investigated around electric double layer. Beside the influence of electric field intensity, it is also found that the transition of periodic flow to chaotic flow is frequency dependent. The frequency of AC electric field is also a control parameter of flow state and determines the routes to chaos.