Roughness-engineered potential wells for controllable ultrasonic cavitation: Multistage bubble capture–release mechanism revealed by multiscale experiments and simulations

Controlling cavitation dynamics is essential for optimizing ultrasonic-assisted processing, targeted energy release, and damage mitigation. Here, we propose a structural strategy for tunable cavitation control using roughness-engineered surfaces that generate geometry-induced potential wells. Titanium alloy walls with varying porosity were fabricated via triply periodic minimal surface designs to systematically modulate roughness. High-speed imaging revealed that moderate roughness stabilizes bubble aggregation above the surface, whereas smooth walls fail to retain bubbles and excessive roughness induces perturbation-driven release. Specifically, in the 20 % porosity sample at t = 0.78 ms, multiple larger clusters formed at the center region of the wall, displaying asymmetric shapes and stretched edges, significantly increasing bubble retention time. Molecular dynamics simulations demonstrated that van der Waals–dominated short-range adsorption and localized low-energy zones extend bubble residence time, enabling stable capture. Excessive roughness, however, disrupts potential well uniformity, triggering asymmetric collapse and directed energy release. Integrating experimental and simulation results, we establish a multistage “capture–perturbation–collapse–release” framework for surface-induced cavitation control. This approach could potentially enable targeted cavitation control in ultrasonic cleaning, precision machining, and erosion prevention.