Nanotechnology is a promising therapeutic tool, but present implementations suffer from poor efficacy. My team and I are developing ultrasound-based micro/nanorobots with precise navigation capabilities that can overcome major limitations of existing nanodrugs. Ultrasound is safe, noninvasive, penetrates tissue, and is widely used in medicine, thus ultrasound-based propulsion will provide a much-needed means for advancing microrobot technology and its therapeutic applications.¬

We designed an ultrasound-propelled, microbubble-based microrobotic system inspired by the sticking and rolling of white blood cells along vessel walls. Our robots self-assemble in the presence of ultrasound into a microswarm that requires no prior fabrication and can morph freely, enabling navigation of complex vasculature networks. These swarms can execute up-, down-, and cross-stream motion against flow rates comparable to those in human veins and have been tested in zebrafish embryos; we now aim to move into mouse models. As our robots are based on contrast agents used for imaging, they support real-time visualization, tracking, and directed navigation. Beyond novel strategies for targeted drug delivery, including within solid tumours, our swarms have potential use in diseases such as cerebrovascular accidents and myocardial infarction. Finally, the relative inexpense of ultrasound allows these microrobots to be utilized in limited-resource settings such as developing nations.