Investigation of droplet oscillation on a vibrating elastic plate

Behaviour of a sessile droplet on a vibrating elastic plate is investigated. We obtain experimentally the characteristics of droplet oscillation modes by two high speed cameras recording from side view and top view synchronously. Theoretical shapes and frequencies are compared with those measured in the experiments, and different regimes of the droplet oscillations are explained. Moreover, the circular patterns of the elastic plate oscillations, so-called “Chladni patterns”, were visualized. The radius variations of the nodal lines in the plate with the frequency of the external forcing are well predicted by our theoretical model. We further focus on the influence of the non-uniform amplitude of the plate oscillation on the droplet oscillatory behaviour. It is important to notice that a drop placed at a nodal line oscillates due to the pitch motion of the plate at this line but not due to the plate vertical vibration which is negligible at the nodal line. A droplet located either outside or inside the nodal lines behaves very differently, resulting in potential depinning of the contact line due to the gradient of the plate deflection.