Self-assembled biomimetic superhydrophobic hierarchical arrays

Abstract

Here, we report a simple and inexpensive bottom-up technology for fabricating superhydrophobic coatingswith hierarchical micro-/nano-structures, which are inspired by the binary periodic structure foundon the superhydrophobic compound eyes of some insects (e.g., mosquitoes and moths). Binary colloidalarrays consisting of exemplary large (4 and 30 lm) and small (300 nm) silica spheres are first assembledby a scalable Langmuir–Blodgett (LB) technology in a layer-by-layer manner. After surface modificationwith fluorosilanes, the self-assembled hierarchical particle arrays become superhydrophobic with anapparent water contact angle (CA) larger than 150 . The throughput of the resulting superhydrophobiccoatings with hierarchical structures can be significantly improved by templating the binary periodicstructures of the LB-assembled colloidal arrays into UV-curable fluoropolymers by a soft lithographyapproach. Superhydrophobic perfluoroether acrylate hierarchical arrays with large CAs and small CA hysteresiscan be faithfully replicated onto various substrates. Both experiments and theoretical calculationsbased on the Cassie’s dewetting model demonstrate the importance of the hierarchical structure inachieving the final superhydrophobic surface states