Electrowetting study of jumping droplets on hydrophobic surfaces

Abstract

Recent studies have shown that jumping-droplet-enhanced condensation has higher heat transfer than state-of-the-art dropwise condensing surfaces by -30-40%. Jumping-droplet condensation occurs due to the conversion of surface energy to kinetic energy during the coalescence of microscale droplets, resulting in droplet ejection from the condenser surface. This conversion of energy is fundamentally studied by using electrowetting to decrease the equilibrium contact angle, increasing droplet surface area. Releasing the voltage allows the droplet to release excess surface energy, causing the droplet to jump off the surface. In contrast with previous work, droplets were initially held at a static deformed state. Here, jumping from the surface from this static electrowetting-induced state is demonstrated for the first time. Releasing the voltage caused droplets to jump as high as -2 mm with a maximum conversion efficiency between surface and potential energy of -5%.