Bouncing droplets on nonsuperhydrophobic surfaces

It is known that impinging droplets can rebound off superhydrophobic while tend to wet hydrophilic and hydrophobic surfaces. In this work, we show that water droplets can bounce off nonsuperhydrophobic soft surfaces between lower and upper impact velocity limits. The cause for the rebound of the droplet is hypothesized as the formation of an air film at the interface due to the deformability of the surface when the impact velocity is larger than the lower limit. At large impact velocity, an air bubble is entrapped from the cavity formed during the spreading of the droplet on the surface. This air bubble coalesces with and releases the air film beneath the droplet when the impact velocity is larger than the upper limit, beyond which the surface becomes wetting and the rebound of droplets is not observed.