Browsing by Author "Hyvönen, Jere"

High-intensity and -amplitude focused ultrasound has been used to induce cavitation for decades. Well known applications are medical (lithotripsy and histotripsy) and industrial ones (particle cleaning, erosion, sonochemistry). These applications often use low frequencies (0.1-5 MHz), which limits the spatial precision of the actuation, and the chaotic nature of inertial cavitation is rarely monitored or compensated for, constituting a source of uncertainty. We demonstrate the use of high-frequency (12 MHz) high-intensity (ISPTA=90 W/cm2 ) focused-ultrasound- induced cavitation to locally remove solid material (pits with a diameter of 20 µm to 200 µm) for non- contact sampling. We demonstrate breaking cohesion (aluminium) and adhesion (thin film on a substrate, i.e. marker ink on microscope glass). The eroded surfaces were analyzed with a scanning acoustic microscope (SAM). We present the assembly and the characterization of a focused ultrasound transducer and show quantification of the effect of different sonication parameters (amplitude, cycle count, burst count, defocus) on the size and shape of the resulting erosion pits. The quantitative precision of this method is achieved by systematic calibration measurements, linking the resulting erosion to acoustic parameters to ensure repeatability (sufficient probability of cavitation), and inertial cavitation monitoring of the focal echoes. We discuss the usability of this method for localized non-contact sampling.