Wetting morphologies and their transitions in grooved substrates

Abstract

When exposed to a partially wetting liquid, many natural and artificial surfaces equippedwith complex topographies display a rich variety of liquid interfacial morphologies. In thepresent article, we focus on a few simple paradigmatic surface topographies and elaborateon the statics and dynamics of the resulting wetting morphologies. It is demonstrated thatthe spectrum of wetting morphologies increases with increasing complexity of thegroove structure. On elastically deformable substrates, additional structures in theliquid morphologies can be observed, which are caused by deformations of thegroove geometry in the presence of capillary forces. The emergence of certain liquidmorphologies in grooves can be actively controlled by changes in wettability andgeometry. For electrically conducting solid substrates, the apparent contact anglecan be varied by electrowetting. This allows, depending on groove geometry, areversible or irreversible transport of liquid along surface grooves. In the case ofirreversible liquid transport in triangular grooves, the dynamics of the emerginginstability is sensitive to the apparent hydrodynamic slip at the substrate. Onelastic substrates, the geometry can be varied in a straightforward manner bystretching or relaxing the sample. The imbibition velocity in deformable grooves issignificantly reduced compared to solid grooves, which is a result of the microscopicdeformation of the elastic groove material close to the three phase contact line.