Keywords: biomimicry; dewetting; micropattern; sol-gel; water condensation; wettability
Dewetting of thin polymer films has been extensively investigated as a way to generate patterned surfaces. In this paper, the controlled dewetting of sol-gel thin films induced by solvent annealing is reported. The key factors that control the dewetting process are identified and patterns with tunable diameter between 5 and 80 mu m and tunable height between 1 and 10 mu m are fabricated on a large scale. By changing the chemistry of the sol-gel system, patterns with wetting contrast, consisting of hydrophilic bumps on a hydrophobic layer, are realized. These surfaces are inspired by the exoskeleton of the Namib desert beetle and are amenable to application in atmospheric water capture, as they facilitate condensation and allow for water droplets to roll off at low critical volumes (6-8 mu L), similar to the value predicted for the Namib desert beetle. The approach presented is simple, scalable, and can be applied to a wide range of substrates including glass. Transparent micropatterns are realized with high transmittance in the visible range, suitable for fabrication of coatings on windows or microlens arrays.
