Multiscale structural design and mechanical strain engineering for wettability transition on PS-sphere-based superhydrophobic coatings

The design and fabrication of superhydrophobic coatings with tunable wettability have significant implications for a wide range of applications, including self-cleaning and anti-icing. Achieving the transition from high-adhesion hydrophobic surfaces with the ‘rose petal-like effect’ to low-adhesion surfaces with the ‘lotus effect’ through the manipulation of surface microstructures remains a challenge. Hierarchical superhydrophobic surfaces were fabricated using polystyrene (PS) spheres of varying sizes, enabling the wetting transition from the Wenzel state to the Cassie state. The modulation of the size ratio among assembled microspheres enabled a remarkable transition in surface wettability, with the water contact angle increasing from 131.4° to 158.3° and the sliding angle decreasing from 180.0° to 7.3°, demonstrating the evolution from sticky to self-cleaning superhydrophobic states. Computational fluid dynamics (CFD) simulations were employed to elucidate the influence of microsphere size on the variations in contact angle and sliding angle during the construction of superhydrophobic surfaces. By applying uniaxial strain, the contact angle increased from 158.0° to a peak value of 165.0°, eventually reaching a steady state, demonstrating effective strain-induced modulation of surface wettability. This multiscale engineering approach, which integrates structural design with mechanical strain modulation, provides an effective strategy for developing intelligent coatings with adaptive wettability, paving the way for next-generation functional surface coatings.