EVAPORATIVE DEPOSITION ON SUPERHYDROPHOBIC SURFACES

摘要

Sessile droplets containing colloidal suspensions of latex particles in water are evaporated on temperature-controlled superhydrophobic surfaces of varying geometry. The transient droplet shape and wetting behavior under evaporation are analyzed as a function of surface temperature and morphology. Throughout the evaporation process, the solid-liquid interface is characterized by a constant contact radius evaporation mode (CCR), a constant contact angle evaporation mode (CCA), or a mixed mode of both CCR and CCA. The total evaporation time can be significantly reduced via substrate heating as compared to diffusion-limited evaporation at thermal equilibrium. To describe the spatial distribution of the particle residues left on the surfaces, qualitative and quantitative evaluations of the depositions are presented. The results show that droplet evaporation on superhydrophobic surfaces driven by either diffusion or substrate heating, suppresses particle deposition at the contact line -the so-called 'coffee ring effect' - and signifies the ability to control the location of solute deposits.