Measurement of the lamella thickness during droplet impact onto differently wettable smooth surfaces using an extension of the LASER Pattern Shift Method with naturally occurring patterns.

This study shows that the LASER Pattern Shift Method (LPSM) is a powerful measurement technique for film thickness measurements. In this paper, the approach of the LPSM is extended, which is now able to measure the lamella thickness during droplet impacts on smooth surfaces using the naturally occurring air bubble shadows. With the help of this rather new measurement technique, the influence of different experimental parameters on the lamella thickness could be systematically assessed, e.g., the influence of impact velocity, liquid properties, and surface wettability. Upon comparing the obtained results to an analytical correlation in the literature, good agreement could be found for its validity range.