Shikuan Yang

Surface nano-patterns on substrates are the fundamental structures of various nano-devices. Template-based surface nano-patterning techniques are highly efficient methods in realizing different surface nano-patterns. The time-saving and low-cost fabrication processes of the template-based surface patterning are highly desirable for industry in fabricating different kinds of nano-devices. This tutorial review summarizes the recent advancements in the field of template-based surface nano-patterning, especially focusing on three templates prepared using self-assembly processes: ultra-thin alumina membranes, monolayer polystyrene sphere arrays, and block copolymer patterns. The basic concepts, the general fabrication processes, the structure-related properties, and the device applications of these template-based surface nano-patterning techniques are introduced.

Enhancing the mobility of liquid droplets on rough surfaces is of great interest in industry, with applications ranging from condensation heat transfer to water harvesting to the prevention of icing and frosting. The mobility of a liquid droplet on a rough solid surface has long been associated with its wetting state. When liquid drops are sitting on the top of the solid textures and air is trapped underneath, they are in the Cassie state. When the drops impregnate the solid textures, they are in the Wenzel state. While the Cassie state has long been associated with high droplet mobility and the Wenzel state with droplet pinning, our work challenges this existing convention by showing that both Cassie and Wenzel state droplets can be highly mobile on nanotexture-enabled slippery rough surfaces. Our surfaces were developed by engineering hierachical nano- and microscale textures and infusing liquid lubricant into the nanotextures alone to create a highly slippery rough surface. We have shown that droplet mobility can be maintained even after the Cassie-to-Wenzel transition. Moreover, the discovery of the slippery Wenzel state allows us to assess the fundamental limits of the classical and recent Wenzel models at the highest experimental precision to date, which could not be achieved by any other conventional rough surface. Our results show that the classical Wenzel eq (1936) cannot predict the wetting behaviors of highly wetting liquids in the Wenzel state.