Anti-frosting characteristics of superhydrophobic-hydrophilic wettability switchable surfaces

Abstract

Combining hydrophobicity with hydrophilicity on hybrid surfaces generates unique phenomena in anti-frosting. However, limited attention has been paid to investigate the anti-frosting effects of wettability switchable surfaces in response to temperature changes. Herein, frosting and defrosting characteristics of thermo-responsive, wettability switchable surfaces are investigated. Specifically, the wettability switchable surfaces are successfully fabricated by coating a poly(ε-caprolactone) (PCL) layer onto the microstructured aluminum substrates, resulting in the wettability transition from superhydrophobicity with an apparent contact angle of water droplet as 152° in the surface temperatures under 60 °C to hydrophilicity with an apparent contact angle of water droplet as 63° in the surface temperatures over 60 °C. The wettability transition capabilities of the surfaces not only enable excellent frost retardation comparable to superhydrophobic surfaces in frosting process, but also realize fast full drying capabilities slightly shorter than superhydrophilic surfaces in defrosting process. The unique feature of wettability switchable surfaces represents an effort to combine the distinct advantages of superhydrophobic and superhydrophilic surfaces to realize anti-frosting functionalities.