Evaporation control of sessile water drops by soft viscoelastic surfaces

In this paper the evaporation of sessile water drops on soft viscoelastic substrates is investigated. We demonstrate how the deformation of the substrate close to the triple-phase contact line influences the evaporation of a sessile drop by using surfaces with similar wettability, but different viscoelastic properties. We show that water drops on soft surfaces (Young's modulus similar to 0.02 MPa) evaporate faster than those on hard surfaces (Young's modulus similar to 1.5 MPa). The faster evaporation rates on soft surfaces can be related to a different dynamic evolution of the receding contact angle, which is a direct consequence of the substrate deformation close to the triple-phase contact line. By adjusting the substrate softness we are able to control the transition between constant contact radius and constant contact angle evaporation modes.