Wetting dynamics under periodic switching on different scales: characterization and mechanisms

The development of substrates with a switchable wettability is proceeding and the limit of switching frequencies and contact angle differences between substrate states has developed in the past years. In this paper we investigate the behavior of a droplet on a homogeneous substrate, which is switched between two wettabilities for a large range of switching frequencies. Here, we are particularly interested in the dependence of the wetting behavior on the switching frequency. We show that results obtained on the particle level via molecular dynamics simulations and on the continuum level via the thin-film model are consistent. Predictions of simple models as the molecular theory of wetting (MKT) and analytical calculations based on the MKT also show good agreement and offer deeper insights into the underlying mechanisms. We study the dynamics of droplets on switchable substrates using continuum and particle-based models and compare the results to the molecular kinetic theory of wetting. The figure shows the switching scheme employing the periodic wettability change.