Characterization of the state of a droplet at a micro-textured silicon wafer using a finite difference time-domain (FDTD) modeling method

In this study, we introduce a finite difference time domain method to study the propagation and reflection of an acoustic wave on smooth and micro-textured silicon surfaces in interaction with droplets in different states. This will enable numerical investigations of interfaces composed of periodically distributed well-defined pillars. One type of transducer was modeled generating longitudinal wave. Three configurations were studied: the Cassie state, the Wenzel state and a composite state for which the droplet collapsed into the middle height of the pillars. After analysis of the displacement along y direction in the silicon wafer, we were able to show that a longitudinal wave is sensitive to the detection of the state of the droplet. The first experimental results made it possible to show a good agreement between modeling and experiments.