Figure 2
From: Long-range spontaneous droplet self-propulsion on wettability gradient surfaces
Surface design and wettability characterization. The size of all the SiO2 stripe is 1 mm × 90 μm × 2 μm. (a) Top view schematic of the gradient surface. From left to right, the pattern densities are 0, 0.33, 0.40, 0.50, 0.59, 0.71, 0.91, 1, and the space between SiO2 stripes are 180 μm, 135 μm, 90 μm, 63 μm, 36 μm, 9 μm, 0 μm, respectively. (b) Undercut structure of solid-liquid contact region. (c) The static contact angle (SCA) and hysteresis contact angle (HCA) of water droplet on each region of the gradient surfaces.
