Fig. 1: Experimental method.

a The experimental setup, schematised here, featuring a high-speed camera (159090 fps) and a 2.5 MHz high-intensity focused US (HIFU) transducer, allows the study of a water-submerged superhydrophobic surface placed at the focus of co-axial optical and acoustic fields. The response of the plastron to an amplitude-modulated (AM) US pulse takes the shape of interfacial perturbations travelling along the gas-water interface from the acoustic focal point, the ripples with same coherence forming patterns of concentric circles, schematised in (b). c An exemplary image acquired by Scanning Electron Microscopy shows the details of a superhydrophobic sample with pillar spacing s = 25 μm and height h = 25 μm. d For the same pillar geometry, the wave frequency as a function of the applied AM frequency always exhibits a 2:1 ratio, demonstrating the control of the frequency of the produced plastronic waves. e The axisymmetric field of acoustic pressure produced by the HIFU transducer was measured in a free field (in the absence of a superhydrophobic surface) using a needle hydrophone. f The radial waves at the gas-water interface (s = 25 μm, h = 25 μm) are optically assessed from the top-view refraction patterns induced by the moving gas-water interface. The wave analysis based on the tracking of the wavefronts, i.e., the wave lines of same phase, normally done in polar coordinates (Details in SI, Figs. S10 and S11), is here conceptualised on an unprocessed high-speed footage.