Ultrasound Imaging and Tracking of Micro/Nanorobots: From Individual to Collectives

The rapid development of untethered micro/nanorobots enables them to be applied in biomedical tasks, such as targeted delivery, localized diagnostics, and minimally invasive surgery. However, many challenges remain before applying these tiny machines to perform therapeutics and intervention in a living body. Among them, one critical issue is the integration of medical imaging systems with micro/nanorobotics to acquire precise feedback in vivo. Ultrasound imaging, as one of the widely used mature imaging technologies, shows great potential for providing real-time feedback of micro/nanorobots in 2-D and 3-D space. In this mini-review, the recent progress and challenges on the imaging and tracking of micro/nanorobots using established medical ultrasound imaging technologies are surveyed and summarized. The limitations together with future research opportunities in the real-time navigation of micro/nanorobots in vivo and their collectives are discussed.