Hydrophobic/superhydrophobic reversible smart materials via photo/thermo dual-response dynamic wrinkled structure

Superhydrophobic materials have attracted considerable scientific interest owing to their excellent properties such as self-cleaning ability, which are attractive for real-world applications. However, challenges still exist in realising smart superhydrophobic surfaces with reversible properties. Although there are many studies on reversible surfaces, most of them have tedious preparation processes or are difficult to achieve, in which the structure requires continuous stimuli to be maintained. Hence, we propose a novel and simple strategy to obtain superhydrophobic/hydrophobic reversible smart materials. Anthracene-terminated photo/thermo dual-response polyurethane was prepared as a dynamic substrate whose wrinkled structure could appear and disappear reversibly through dimerisation and depolymerisation of the anthracene groups. Thereafter, modified SiO2 sol was applied as the hydrophobic coating because the aggregation of SiO2 produces micro-nano structures on the surface wrinkles. The good synergistic effects of the wrinkles and nanoparticles enhance the roughness, realising superhydrophobic materials. These smart materials can reversibly convert into a hydrophobic or superhydrophobic wetting state, induced by UV exposure or heating, in which both states stable under normal conditions. Moreover, these superhydrophobic materials have many attractive properties, such as self-cleaning, durability, and environmental friendliness. The novel method used to fabricate dynamic wrinkles also has many potential applications in other areas such as triboelectric nanogenerator reversible switching of adhesion, and dynamic microfluidic channels.