Droplet Migration Characteristics on Liquid-Infused Surfaces by Mechanical Vibration

In industrial applications such as condensation heat transfer, frost suppression, and fog collection, the droplet in the Wenzel state exhibits a strong adhesion to the surface, hindering its migration. To prevent the wetting transition and improve droplet migration, a novel method by combining wettability gradients, liquid infusion, and mechanical vibration is proposed in this paper. A curved microgrooved surface with gradient wettability is fabricated via photolithography on a silicon wafer, and then, silicone oil is infused to form the liquid-infused surface. Subsequently, a vertical vibration is applied to induce droplet deformation, enhancing directional migration. To characterize droplet deformation, the maximum deformation coefficient (β_m) is introduced, and it consistently varies with the average migration velocity (v_avg). The effects of vibration parameters, surface area fraction, droplet volume, and surface tension on v_avg and β_m are analyzed. Results indicate that the vibration deformation of droplets changes with vibration frequency. At the resonance frequency, the droplet exhibits significant stretching and spreading, resulting in a marked increase in v_avg. Furthermore, there exists an optimal amplitude at the resonance frequency. Additionally, reducing the solid area fraction significantly weakens contact line pinning, further increasing the v_avg and β_m. As the droplet volume and surface tension increase, both v_avg and β_m increase. Experimental results and theoretical analysis reveal a linear correlation between β_m and CaOh^-1. This work provides theoretical and technical insights into controlling droplet migration, offering a new perspective for optimization in industrial applications.