Prototyping of Superhydrophobic Surfaces from Structure-Tunable Micropillar Arrays Using Visible Light Photocuring

A new approach is reported to fabricate micropillar arrays on transparent surfaces by employing the light-induced self-writing technique. A periodic array of microscale optical beams is transmitted through a thin film of photo-crosslinking acrylate resin. Each beam undergoes self-lensing associated to photopolymerization-induced changes in the refractive index of the medium, which counters the beam's natural tendency to diverge over space. As a result, a microscale pillar grows along each beam's propagation path. Concurrent, parallel self-writing of micropillars leads to the prototyping of micropillar-based arrays, with the capability to precisely vary the pillar diameter and inter-spacing. The arrays are spray coated with a thin layer of polytetrafluoroethylene (PTFE) nanoparticles to create large-area superhydrophobic surfaces with water contact angles greater than 150° and low contact angle hysteresis. High transparency is achieved over the entire range of micropillar arrays explored. The arrays are also mechanically durable and robust against abrasion. This is a scalable, straightforward approach toward structure-tunable micropillar arrays for functional surfaces and anti-wetting applications.