Fast Locomotion of Microrobot Swarms with Ultrasonic Stimuli in Large Scale

In recent years, the acitve motion of micro-nano machines has received wide attention due to its potential applications in biomedicine, biosensing, pollution control and other fields. However, the rapid manipulation of microrobot swarms in a large range is still an unmet challenge. With merits of simple structure, rapid response, and biocompatibility, ultrasonic power has been emerging as one of the most suitable methods to accomplish locomotion for microrobots. Here we demonstrate a fast moving strategy of microrobot swarms with ultrasonic stimuli in a relatively large scale. Both aggregation and dispersion patterns are conducted in a manipulation reservoir with 6 mm in diameter. The aggregation of microrobot swarms is achieved by acoustic radiation force caused by acoustic pressure gradient, which drives the microrobots migrate towards the nearest sound pressure node. The dispersion behavior of the microrobots is driven by the acoustofluidics, which is caused by the localized traveling wave motion of the vibrating substrate under ultrasonic stimuli. Both modes of swarming are completed in several seconds, indicating the great promise for rapidly steering microrobot assembly in diverse potential applications.