Evaluation of atmospheric-pressure plasma parameters to achieve superhydrophobic and self-cleaning HTV silicone rubber surfaces via a single-step, eco-friendly approach

Abstract

Effective self-cleaning and superhydrophobic surfaces having superb water repellency are among the most widespread alternatives for eliminating surface contamination, corrosion resistance, reducing ice accumulation, etc. to enhance the life-span of various engineered materials. In this study, we developed a simple methodology, based on an atmospheric-pressure air plasma system, as a simple, environmentally friendly and industry applicable approach for fabricating superhydrophobic surfaces. Our approach is significant as the use of an atmospheric-pressure plasma system combined with compressed air as an eco-friendly plasma gas offers great potential for the industrialization of superhydrophobic surfaces for mass production. The creation of micro- and nano-structured surface roughness on a low surface energy high temperature vulcanized (HTV) silicone rubber substrate resulted in a static water contact angle (WCA) > 160° and a contact angle hysteresis (CAH) < 3°. Scanning electron microscopy (SEM) revealed the presence of the plasma-induced coral-like micro- and nano-structures responsible for the superhydrophobicity of the surfaces. We assessed the influence of plasma operating parameters on the water repellency of silicone rubber via a design of experiment (DoE) method to determine the near-optimal operating parameters; once established, we could assess the characteristics of the surfaces. In addition to the superhydrophobic surfaces, we also fabricated another surface, named a slippery hydrophobic surface, under specific plasma operating conditions. Superhydrophobic surfaces prepared at these optimal plasma operating conditions showed favorable water repellency and self-cleaning properties under both wet and dry conditions.