Curvature-mediated dynamics of photothermal cavitation bubbles at solid–liquid interfaces

Cavitation bubbles at solid–liquid interfaces are central to microfluidic actuation, biomedical manipulation, cleaning, and erosion. So far, the effect of surface curvature on cavitation bubbles remains insufficiently understood. Here, we investigate photothermal cavitation bubbles generated on a planar gold-nanoparticle substrate and on microspheres of varying diameters using high-speed imaging and numerical simulations. Bubbles on both surfaces exhibit similar early expansion, producing strong transient pressure that dominates the peak force and impulse. Planar walls promote stable hemispherical attachment with pronounced necking collapse, whereas spherical surfaces induce curvature-controlled transitions from partial attachment to full encapsulation. These curvature-dependent effects arise primarily during collapse, when curved interfaces reshape pressure gradients, modify reentrant inflow, and alter collapse morphology. These behaviors scale with the ratio of the maximum bubble width to microsphere diameter, which governs near-wall flow asymmetry, shifts collapse-induced pressure focusing, and determines both the transient force and accumulated impulse transmitted to the surface. Furthermore, a mathematical model was developed to establish quantitative relationships between the accumulated impulse, bubble size, and interface curvature for both planar and spherical surfaces, and its validity was confirmed through numerical simulations. Overall, these results establish a unified framework for curvature- and size-dependent cavitation dynamics.