Dynamic equilibrium in time-varying oscillating sessile droplet subjected to vertical vibration

We have studied the motion of liquid drops on an aluminum surface subject to vertical vibrations. By combining with a laser Doppler vibrometer (LDV) system, a novel experimental setup was utilized to study the droplet’s motion. At sufficiently low oscillating amplitudes, the drops are pinned to the surface at beginning, after applied higher voltage, the drops began spreading motion and reached a dynamic re-equilibrium state. Images taken with a fast camera show that process, and the equilibrium equation described the droplet’s behavior. Force analysis revealed the interplay between capillary, friction, and vibration forces during spreading state. A derived governing equilibrium equation allowed for fit the experiment data of droplet radius after the dynamic motion. The research has potential applications in microfluidic devices and surface wettability control.