Reversible wettability transition between superhydrophilicity and superhydrophobicity through alternate heating-reheating cycle on laser-ablated brass surface

Abstract Functional surfaces with reversible wettability transition between superhydrophobicity and superhydrophilicity have attracted much attention due to their potential applications in self-cleaning, anti-icing, anti-fogging, anti-biofouling, and oil-water separation, along with smart membranes, sensors, and microfluidic devices. In order to achieve such transition, the surface wettability or intrinsic Young contact angle must be able to reversibly change upon being stimulated by external factors. Meanwhile, the surface structure must have sufficient ability to magnify this change in the surface wettability. For metals, metallic oxides and some other materials, the surface wettability can be changed by controlling adsorption and decomposition of airborne organic compounds on these surfaces via different methods such as ultraviolet irradiation, long-term storage at room temperature and heating treatments and their combinations. In this study, we reported for the first time that such transition can be realized on a laser-ablated brass surface by using alternate heating-reheating cycles. Our study demonstrated that the reversible change in the Young contact angle of the substrate material caused by the adsorption and decomposition of airborne organic compounds and a great reduction in the width of the Wenzel region separating the Cassie-Baxter region and the full wetting region caused by the micro/nano-scale hierarchical structure are responsible for the observed transition.