Spontaneous Adsorption-Induced <i>Salvinia</i>-like Micropillars with High Adhesion
Zhen Shi, Zejun Zhang, Wei Huang, Hang Zeng, Vilko Mandić, Xin Hu, Lizhong Zhao, Xuefeng Zhang
Abstract
Superhydrophobic surfaces with high adhesion provide high potential for underwater applications. Inspired by Salvinia leaf, here, we have reported a simple method for fabricating adhesive Salvinia-like micropillars via photolithography and spontaneous adsorption of organic molecules from the atmosphere. With continuous hydrocarbon adsorption on sputtered cerium dioxide (CeO2) films, the surface gradually evolved and eventually became chemically heterogeneous. Huge wetting contrast from superhydrophilic to superhydrophobic over exposure time was observed; meanwhile, the wetting mode changed from the Wenzel (W) state to Cassie-Baxter (C-B) state. As a result, hydrophobic hydrocarbons (C–C/C–H) and trapped air between adjacent pillars contributed to the high apparent contact angle (CA), while the hydrophilic domains of C–O/O═C–O and CeO2 on the top layer made the surface highly adhesive with water droplets. In comparison with traditional fluorinated superhydrophobic surfaces, CeO2-coated surfaces showed high adhesive force with water droplets and can be used as a “mechanical hand” for water droplet transport. The adsorption-induced Salvinia-like micropillars with high adhesion may find many other droplet-based applications in microfluidic fields.