Splashing impact of a single drop onto very thin liquid films

Liquid films with thicknesses on the order of 1 mm were commonly used for the study of drop impingement onto a wetted surface. This is because films thinner than 1 mm are difficult to generate and measure due to capillary meniscus. In this work a novel method to produce thin films of well-defined thickness has been developed. Also a reliable process with minimum uncertainty to determine film thickness was proposed. New splashing phenomena were observed for drop impact onto thin films. It is found that the critical splash level (the threshold Weber number) is insensitive to film thickness for a given solid surface if the film is sufficiently thin. It is also shown that the critical splash level increases with liquid viscosity.