Vibration-based surface treatment considering viscous penetration length

Abstract

Functional surfaces can be made to produce various effects by modifying the surfaces of materials. To make functional surfaces for various industrial fields various methods have been used to modify and control the wettability of the surface. In this study, we focused on treating the wettability of a liquid film surface by applying vertical high-frequency vibration. Especially, the relationship between the vibration and the coating film thickness was carefully investigated, to ensure the maximum roughness control in thin liquid films. For surface roughness analysis, three methods were used. First, we measured the contact angle using high speed camera. In results, as frequency increases, contact angle decreases while as voltage increases, contact angle increases. Second, we measured surface roughness using displacement sensor. As a result, both surface wavelength and amplitude decreased as frequency increased. Third, we analyzed the surface shapes of the samples produced with differing viscosity, frequency, and voltage of the applied vibration. As a result, as frequency increases, or viscosity or voltage decrease, the change in the surface shape decreases. It means the surface roughness is decreased. We found that it was necessary to optimize the liquid film thickness in consideration of the damping effect or viscous penetration length when performing surface treatment using vibration. These findings confirm that it is necessary to optimize the process by taking into account the vibration, viscosity and film thickness for proper film surface treatment, and that surface treatment using the vibration method can be productively used in various industrial fields.