Development and calibration of the LASER Pattern Shift Method for measuring the lamella topology during drop impact on walls

Spreading behavior of droplets impinging on flat walls have been and still are often investigated. However, the experimental investigation of the lamella thickness and shape is very difficult due to the outer rim hiding the inside. For these investigations a new measurement method was developed measuring the lamella height profile along one axis. Additionally, this method can be used for time-resolved monitoring of lubricating films and component spacing in the range of a few micrometers up to several millimeters. This paper validates the proposed technique presenting the derivation of the describing equation and the experimental setup. For validating the thickness measurement of the lamella during a droplet impact, the time dependent film thickness of an evaporating isopropanol film with an initial thickness of approximately 300μm is measured. The results of the newly proposed method using a LASER line as pattern are compared to a commercial system based on confocal chromatographic interference (CCI) and an analytical solution for the mass transfer.