A Cymbal Transducer as a Single-Element Device for Enhanced Cavitation Generation

Cavitation driven by low-frequency ultrasound has been widely recognized as an effective method of transdermal drug delivery, but challenges remain regarding the size and efficiency of the sonicator. The cymbal transducer is a promising candidate for such applications; however, the conventional design is limited by its relatively low power output and difficulty in manufacturing with consistency, limiting its success in arrays and for extended treatment times. This study introduces a modified cymbal transducer, operating at 66.2 kHz, designed to offer higher output pressure and an easier fabrication process, while being compact (OD = 36 mm and Thk = 6 mm). The transducer was then characterized in terms of its vibration mode shape, acoustic pressure field, acoustic power, and cavitation performance captured through high-speed imaging and acoustic detection of bubble-collapse shockwave emissions. Furthermore, the device was employed to permeate fluorescent nanoparticles (10 kDa) into agar-based phantom. The new design is capable of outputting up to 3.05-MPa peak negative pressure (PNP) at its focal region (MI = 11.8), and spatial peak temporal average intensity (ISPTA) of 1.59 W/cm2, significantly surpassing other devices. High-speed shadow graphic imaging reveals superior cavitation performance that has not been demonstrated in prior studies. The transducer is also capable of delivering nanoparticles at a rate of 1.19 mm/min into the phantom. As a result, the modified cymbal proved to be not only a robust sonicator with potential for sonophoresis but also viable as a compact power ultrasonics source.