Engineering Ultrasound Fields to Power Medical Micro/Nanorobots

Increasing demand for precision medicine devices has led to the development of self-propelled nano/microdevices capable of operating at small scale while performing biomedical tasks. This work intends to highlight the most recent advances on ultrasound propelled micro/nanorobots and provide an insight into the challenges and their future applications. Diverse types of acoustic fields have been used to power microrobots. Focused ultrasound (FU) is capable of concentrating acoustic energy in a single zone, optimal for applications where high penetration or localized actuation is required. In addition, standing wave ultrasound (SWU) robots work on nodal planes, have demonstrated multiple advanced biomedical tasks, suitable for lab-on-a-chip applications. Finally, traveling wave ultrasound (TWU) employs tunable resonant elements responding to specific frequencies, holding great promise for in-vivo applications. Methods to propel microrobots with acoustic field are presented: FU, SWU, and TWU. Including their setup, design, propulsion mechanism, and applications.