Ultrasound‐Controlled Swarmbots Under Physiological Flow Conditions

Abstract

AbstractNavigation of microrobots in living vasculatures is essential in realizing targeted drug delivery and advancing non‐invasive surgeries. Acoustically‐controlled “swarmbots” are developed based on the self‐assembly of clinically‐approved microbubbles (MBs). Ultrasound is noninvasive, penetrates deeply into the human body, and is well‐developed in clinical settings. This propulsion strategy relies on two forces: the primary radiation force and the secondary Bjerknes force. Upon ultrasound activation, the MBs self‐assemble into microswarms, which migrate toward and anchor at the containing vessel's wall. A second transducer, which produces an acoustic field parallel to the channel, propels the swarms along the wall. Noting that human arteries have a blood flow 5–19 cm s−1, powerful features of cross‐ and upstream swarmbot navigation are demonstrated against physiologically‐relevant flow rates that reach 16.7 cm s−1. Additionally, controlled navigation of swarmbots is shown within mice blood and under pulsatile flow conditions of 100 beats per minute (bpm); an adult human heart at rest executes between 60 and 100 bpm. This capability represents a much‐needed pathway for advancing preclinical research.