Transparency and superhydrophobicity of cone-shaped micropillar array textured polydimethylsiloxane

Abstract

Transparent superhydrophobic surfaces have great potential for application to self-cleaning transparent windows. We suggest a fabrication method that combines laser beam machining and polymer casting. A UV nanosecond pulsed laser was used to machine arrays of holes into molds composed of 6061 aluminum alloy. Then, polydimethylsiloxane was cast into the laser-machined molds. To study the effects of the array geometry on superhydrophobicity and transparency, a series of micropillar arrays with different step sizes were fabricated. As a result, the critical step size at which the surfaces changed from hydrophobic to superhydrophobic was found to be approximately 80 μm. Cone-shaped micropillar arrays with 80 μm step size showed 175° maximum water droplet contact angle and were highly transparent throughout the 300–1000 nm spectral region. Sliding angle was observed to confirm the surfaces’ self-cleaning ability. This work opens up the possibility of mass production of superhydrophobic, transparent, self-cleaning surfaces.