Superhydrophobic, mechanically durable, highly transparent surface covered with CuO/PDMS composite nano-tips using one-step wet oxidation process of Cu/PDMS multilayer

In this study, a mechanically durable, transparent, and superhydrophobic CuO/polydimethylsiloxane (PDMS) composite nano-tips surface was fabricated by a wet oxidation process of a Cu/PDMS multilayer structure. A growth mechanism for the CuO/PDMS composite nano-tips was proposed accounting for the superhydrophobic characteristics of the CuO/PDMS nanostructured surface: During wet oxidation, as CuO nanowires form and grow, the PDMS surface in contact with Cu is dragged up along the CuO nano-tips surface, eventually becoming a CuO/PDMS nanocomposite superhydrophobic surface. The fabricated CuO/PDMS nano-tips surface showed superhydrophobicity with a water contact angle of 158 degrees, and optical transmittance of up to 93.8 % in the 400-700 nm wavelength range. Additionally, the mechanical durability of the fabricated surfaces was also investigated. Repeated touching force (-1.0 kgf), stretching (-100 %), and bending (-100 degrees) 1000-cycle test results confirm the mechanical durability of the CuO/PDMS nanostructured surface. As a mechanically durable, transparent, and superhydrophobic film, the CuO/PDMS nanostructured surface was used as protective film for a touch screen. This study offers novel insights into the durability of artificial superhydrophobic surfaces and the synthesis methods of metal oxide-polymer nanocomposites.