Visualization of Flows around a Wide Au-Coated Beam in Valving Motion Understood as AC Electroosmosis

Recently, bio-inspired devices have attracted much attention. In particular, elastic valves using AC electroosmosis (ACEO) hold promise for the development of artificial cilia in future microfluidic applications because of their simplicity and high-performance multi-functionality. However, direct evidence of ACEO-driven large valving motion has not been obtained yet. In this study, we report experiments that a wide Au-coated plastic-film beam shows large valving motion in water. By visualizing the flow fields during the motion, we show that the large valving motion of the wide Au-coated beam is understood to be due to ACEO occurring at the edge of the beam. Furthermore, we found that the wide beam was elevated largely by the effect of the vortex flow (understood to be the flow due to ACEO at the beam edge) and the incoming lift flow into the rearward region of the valve. We believe that our findings contribute significantly to realizing new artificial cilia.