Fig. 4.

Miniaturized ultrasonic transducers. (A) An ultrasonic transducer for non-invasive ultrasound transdermal drug delivery. (Adapted from [157], copyright 2018 IOP Publishing). (B) Piezoelectric single crystal ultrasonic transducer for endoscopic drug release to the gastric mucosa. (Adapted from [51], copyright 2021 IEEE). (C) Piezoelectric microtransducers for localized cavitation. (Adapted from [158], copyright 2023 The Author(s)). (D) An ultrasonic transducer that is capable to produce both therapeutic and diagnostic ultrasound in a single device, demonstrated for thermal ablation and high-resolution imaging. (Adapted from [159], copyright 2021 by the authors). (E) Low frequency ultrasound applicator for chronic wound treatment. (Adapted from [161], copyright 2019 IEEE).