Modulating Wetting States of Molten Aluminum Droplets on SiO₂ Surfaces via Vertical Sinusoidal Vibrations

Vibration affects the wetting behavior of droplets, and it is feasible to use vibration to modulate the adhesion characteristics of droplets. In this paper, the effect of vertical sinusoidal vibrations on the wettability of molten aluminum droplets on the substrate surfaces of smooth and with nanopillars is investigated. The increase in the frequency or amplitude of the vibration leads to a rise in the interfacial potential energy between the molten droplets and the substrate, which in turn leads to the occurrence of the Wenzel-Cassie transition. Once the vibration frequency reaches the threshold values, the molten droplets leave from the substrate, that is, dewetting occurs. The molten droplets in the Wenzel state undergo a Wenzel-Cassie transition before dewetting occurs. A phase diagram describing the frequency thresholds at which the molten aluminum droplets undergo dewetting and the Wenzel-Cassie transition at different amplitudes is plotted. For a specific amplitude, the frequency of vibration required for dewetting to occur in molten aluminum droplets in the Young state is lower than that in the Wenzel state. The needed vibrational frequency for dewetting or the Wenzel-Cassie transition decreases with increasing amplitude.