Experimental investigation of chaotic induced-charge electro-osmosis

Near-surface chaotic induced-charge electro-osmosis (ICEO) was numerically predicted on a metallic cylinder some years ago [Davidson et al., "Chaotic induced-charge electro-osmosis, " Phys. Rev. Lett. 112, 128302 (2014)]. However, no systematic experimental investigation has yet been conducted on this problem. In this paper, we experimentally observed that ICEO is stable in weak electric fields and becomes chaotic in strong electric fields. Unlike the numerical prediction, the observed chaotic ICEO is irregular and unstable across the whole velocity field. The chaotic ICEO flow pattern varies significantly with time. The chaos degree grows upon increasing the electric field. Moreover, the critical electric field at which the ICEO transits from the stable to chaotic state shows a dependence on the sodium chloride concentration and electric field frequency. The new findings can contribute to the understanding of ICEO and facilitate the development of ICEO-based micro- and nano-fluidic applications.