Electrowetting Actuation Methods for Surface Morphology Control of Multifunctional Composites

摘要

able new system-level functionality by affecting surface airflow, heat transfer, andrnoptical reflectivity. NRL has been developing this capability with a new class of twophasern(solid-liquid) composites having both structural functionality and active surfacernroughness control. These ‘poro-vascular composites’ (PVCs) consist of polymerrnlaminates with an internal vascular network filled with a liquid and connected to anrnarray of pores on the surface. By controlling the shape and the height of the liquidrnmenisci in the pores, the overall surface morphology can be changed from bumpy tornsmooth to dimpled. It is proposed to control the liquid shape and height using arncombination of volume-displacement pumping and Electrowetting-on-Dielectricrn(EWOD), which is a convenient method to modify the liquid-solid contact angle withrnan applied voltage. The interrelated effects of surface tension, electrowetting forces,rnliquid-solid contact angle, pressure, and microfluidic flow are non-intuitive in PVCrngeometries. We present models of the relevant physical phenomena and apply them inrnthe design of liquid height / shape control in PVCs for several different scenarios,rnincluding a single electroded capillary, EWOD on the substrate surface, and EWODrninside the reservoir or a connected microchannel. We show that while there arernimplicit limitations, large contact angle changes can be achieved, particularly ifrnvolumetric pumping is included.