Magnetically Responsive Superhydrophobic Surface with Reversibly Switchable Wettability: Fabrication, Deformation, and Switching Performance

Responsive surfaces with reversibly switchable wettability have attracted widespread attention due to their diverse range of potential applications in the past few years. As a representative example, the magnetically actuated dynamic regulation structured surfaces provide a convenient and unique approach to achieving remote control and instantaneous response. However, (quasi)quantitative design strategies and economical fabrication methods with high precision for magnetically responsive surfaces with both superhydrophobicity and superior wetting switchability still remain challenging. In this work, a manufacturing technique for high-aspect-ratio magnetically responsive superhydrophobic surfaces (MRSSs) via the integration of micromilling, replica molding, and coating modification is proposed. The geometrical parameters of magnetic micropillar arrays (MMAs) on the surface are specially designed on the basis of the Cassie-Wenzel (C-W) transition critical condition in order to guarantee the initial superhydrophobicity of the surface. Benefiting from the reconfigurable microstructures of MMAs in response to magnetic fields (i.e., shifting between upright and curved states), the wettability and adhesion of MRSSs can be reversibly switched. The smart wetting controllability presented on MRSSs is proven to be largely determined by the geometrical parameters and deformation capacity of the micropillars, while the visible wetting switching is mainly ascribed to the variation in wetting regimes of droplets. The modification of the superhydrophobic coatings on the micropillar top is also demonstrated to be capable of further enhancing the initial hydrophobicity and switchable wettability of surfaces, producing water droplets with a volume of 4-6 μL to exhibit the reversible switch from low adhesive superhydrophobicity to high adhesive hydrophilicity. In addition to providing an alternative fabrication strategy, this work also presents a set of design concepts for more applicable and sensitive MRSSs, offering a reference to both fundamental research and practical applications.