Figure 5. Drop bouncing behaviour on a concave surface.

Selected snapshots showing a drop (D₀=2.9 mm) impacting on the concave surface (with a diameter of curvature D=8.0 mm) at We=7.9 both from the side view (a) and plan view (b). After spreading to its maximum extension in the azimuthal direction at 3.0 ms, the drop continues its spreading in the axial direction and reaches its maximum spreading at 6.6 ms. It finally bounces off the surface after a contact time of 10.3 ms, reduced by ∼40% compared with that on a symmetric surface. More details are shown in Supplementary Movie 3.