Photomanipulation of a Droplet by the Chromocapillary Effect

摘要

Operations (driving, mixing, and handling) with small amounts of liquid usually rely on complex architectures that involve active (pumps and valves) and passive (channels) elements. Manipulation of liquid droplets by light is thus a promising yet challenging alternative. The most common strategy toward this goal uses solid surfaces with specific photosensitive surface properties. When a liquid droplet is deposited on such substrates, illumination by light induces a gradient of wettability to result in simple and low-speed motion (ca. 30 μm s~(-1)) of the droplet. Herein we show that light can be used to create a wavelength-dependent interfacial tension gradient at a liquid/liquid interface, thus inducing an interfacial flow that is able to generate droplet motion in the opposite direction to the gradient.