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Study of Oscillating Electroosmotic Flows with High Temporal and Spatial Resolution

Zhao, Wei, Liu, Xin, Yang, Fang, Wang, Kaige, Bai, Jintao, Qiao, Rui, Wang, Guiren
Analytical chemistry 2018 v.90 no.3 pp. 1652-1659
electric field, electroosmosis, fluorescence, photobleaching, temporal variation, velocimetry
Near-wall velocity of oscillating electroosmotic flow (OEOF) driven by an AC electric field has been investigated using a laser-induced fluorescence photobleaching anemometer (LIFPA). For the first time, an up to 3 kHz velocity response of OEOF has been successfully measured experimentally, even though the oscillating velocity is as low as 600 nm/s. It is found that the oscillating velocity decays with the forcing frequency ff as ff–⁰.⁶⁶. In the investigated range of electric field intensity (EA), below 1 kHz, the linear relation between oscillating velocity and EA is also observed. Because the oscillating velocity at high frequency is very small, the contribution of noise to velocity measurement is significant, and it is discussed in this manuscript. The investigation reveals the instantaneous response of OEOF to the temporal change of electric fields, which exists in almost all AC electrokinetic flows. Furthermore, the experimental observations are important for designing OEOF-based micro/nanofluidics systems.