Wed December 18th 2013
Seminar Spontaneous Wetting and Drop Impact on Soft Substrate
Longquan Chen


Wetting phenomena on soft substrates are commonly encountered in our daily life, from washing hands, to painting a wall, to lubricating our eyes several times per minute. However, wetting dynamics on soft substrates is still not well understood. The first part of this presentation will focus on the spontaneous wetting on soft substrates. It was found that the early rapid spreading of liquids on soft substrates is similar to that on rigid surfaces. The dynamics is independent on the substrate softness, and is dominated by inertia and capillary forces. However, the duration of the inertial wetting is normally shorter on soft substrates than that on rigid surfaces, and it depends on substrate softness. This is because inertia lessens and viscoelastic dissipation in the soft substrate dominates the wetting as spreading proceeds. In the second part of the talk, drop impact phenomena on soft substrates will be introduced. It was observed that water droplets can bounce off nonsuperhydrophobic soft substrates between lower and upper impact velocity limits. The secret of the rebound drops is due to the formation of an air film at the interface on the deformable substrate when the impact velocity is larger than the lower limit. With a larger impact velocity, an air bubble is entrapped from the cavity formed during the spreading of the droplet on the substrate. This air bubble coalesces with and releases the air film beneath the droplet when the impact velocity is larger than the upper limit, which leads to the wetting of soft substrate and the sticking of droplets.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing