High-intensity focused ultrasound (HIFU) is commonly used for cavitation-induced localized material erosion, typically in the kHz range for breaking biological material for medical applications. HIFU also shows potential for highly localized sampling, with higher frequencies offering better focusing but higher cavitation thresholds. Dual-frequency methods enhance cavitation erosion by lowering the cavitation threshold, usually using two transducers at different kHz ranges. To improve cavitation erosion in the MHz range, this study used one transducer with two MHz signals close in frequency, creating an amplitude-modulated wave with a kHz beat frequency, achieving localized material removal with a reduced cavitation threshold. We studied the effects of frequency mixing on ink removal from microscope slides using one focusing transducer in the MHz regime (4.25 MHz and 4.35 MHz). We compared cavitation erosion marks from frequency mixing and single-frequency sonication. The results show that frequency mixing using a single focused transducer in the MHz regime can enhance material removal.
