3D μ-printing of polytetrafluoroethylene microstructures: A route to superhydrophobic surfaces and devices

Abstract Polytetrafluoroethylene (PTFE) is a fluoropolymer well known for chemical inertness and insolubility, as well as the extreme hydrophobicity that can be achieved. Nonetheless, those unique properties make PTFE difficult to process, PTFE components are usually fabricated from the powder, and later shaped using traditional machining processes. So, although 3D printing can provide flexibility, fast and economically production of on-demand parts, especially complex 3D geometries that are hard or impossible to fabricate by machining processes, attempts to introduce PTFE into 3D printing are extremely rare and difficult. Here, we report a 3D micro-printing (μ-printing) method based on digital ultraviolet (UV) lithography for fabrication of micrometer-scale 3D PTFE structures and investigate their superhydrophobic properties and applications. In this method, PTFE nanoparticles are dispersed in a photocurable solution of polyethylene glycol diacrylate (PEGDA) and then 3D printed into predefined microstructures by layer-by-layer UV projection exposures. Subsequent sintering process removes other polymer with relatively low decomposition temperature to leave pure PTFE microstructure. In the experiments, 3D PTFE microscaffolds for droplet lasers and electrostatic-driven biomimetic water striders have been demonstrated to show the wide applications of the micro/nano-structured superhydrophobic PTFE surfaces as well as the flexible microengineering ability of the 3D μ-printing method.