Wettability-Switchable Azobenzene Inverse Opal Film via Interfacial Engineering

Precise control of surface wettability and droplet dynamics is essential for the development of intelligent interfaces and fluidic devices. However, most existing systems suffer from limited wettability modulation, an irreversible response, or complex fabrication. Herein, we report an azobenzene inverse opal film capable of reversible wettability and adhesion switching under alternating UV/vis irradiation. The wettability was governed by both photoinduced molecular reorientation and surface topography changes. Upon trans-cis photoisomerization, the surface energy increased from 22.0 to 33.5 mJ/m2, accompanied by a rise in the sliding angle from 17° to 25° and a transition in the continuous sliding behavior from rolling to pinning. Importantly, the dynamic modulation was repeatable, fatigue-resistant, and strongly dependent on the crosslinking density of the polymer network. The as-prepared film demonstrated programmable droplet mobility, enabling reversible switching between droplet rolling and pinning. This study addressed the challenge of achieving controllable and reversible wettability on solid surfaces without lubricants or complex lithography and offered a promising strategy for developing smart coatings, self-cleaning materials, and photonic fluidic devices.