Micro-structured Surfaces Inspired from Nature: Fabrication, Characterization and Application

Surfaces that control fluids are significant in self-cleaning, liquid-transport and cell-directing. They are significantly observed on biological surfaces that control wettability and adhesion by means of micro-/nano-structures, and have aroused interest in foundational and biomimetic research. The present work suggests a mass-producible and large-scale fabrication method of superhydrophobic polymeric surfaces by means of templating process using polystyrene (PS) cups, an environmental wastage, which can maximize productivity and cost effectiveness. Here we report on the replication of surfaces of Strelitzia reginae, Colocasia esculenta, Borassus flbellifier, Local sotinag leaves onto thin polymeric films using a template technique. The replication was carried out on polystyrene (PS) film using poly (dimethyl siloxane) (PDMS) molds. The wettability properties of the replicated surfaces were investigated in comparison with those of the original leaves by virtue of contact angle measurements and their corresponding microstructures were analyzed by means of scanning electron microscopy (SEM). Water droplets easily slip or roll down on such surfaces, showing low hysteresis properties. In this paper, we also study the evaporation process of a sessile droplet on different artificially prepared micro-structured PS surfaces, including smooth PS surfaces. The micro-structured surface has an array of high-aspect-ratio micro-wires and is implemented by using a simple template-based fabrication method. It possesses superhydrophobicity allowing the liquid droplets to remain in the ‘fakir’ state throughout the evaporation processes. Sessile droplets of distilled water and water/methanol binary mixture test liquids with their contact angles and base diameters are monitored. The results show that the micro-structures play a critical role in the droplet dynamics during evaporation. This investigation will be helpful to design a novel fluid-controlling surface that can be extended to applications such as self-cleaning, liquid-transport and cell-directed projects.

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