Characterising a high-end ultrasonic toothbrush for its use as a low-cost well sonicator

Overview & Synopsis

Well sonication setups for ultrasound-assisted drug and gene delivery typically comprise multiple single-element ultrasound transducers of centre frequency greater than 1 MHz that are positioned underneath, inside or attached to Petri dishes containing cell mixtures. The number of parallel experiments is limited to the amount of output channels on the power amplifier feeding into the transducers, most commonly four to six. So-called ultrasonic toothbrushes contain a single transducer element, a signal generator, and an amplifier per unit. The brush head and handle base fit inside a Petri dish. In this study, a high-end ultrasonic toothbrush was characterised for its use as a well sonicator. The device was clamped in an aquarium filled with degassed water, whilst the acoustic field was measured at variable positions with a wide-band bullet hydrophone and the physical brush displacement was recorded with a high-speed camera operating at 4 kHz. The device was transmitted quasi-continuous pulses at a 97% duty cycle of narrowband 421-kHz fundamental frequency and 842-kHz second harmonic. In free-air measurements, temperatures rose less than 2K over 1 hour of nonstop sonication. The highest peak-negative pressures measured corresponded to mechanical indices less than 0.1. showing potential for well sonication below the cavitation threshold.