Acoustically powered surface-slipping mobile microrobots

Significance Untethered microrobots have significant applications in medical interventions such as targeted drug delivery. Here, we present an acoustically propelled microrobot that uses a fast and unidirectional surface-slipping locomotion strategy to navigate on both flat and curved surfaces. The three-dimensionally microprinted microrobot contains a trapped spherical air bubble to harness acoustic waves for propulsion at incredibly high speeds, up to 90 body lengths per second with body length of about 25 µm, and it can be steered by external magnetic fields. The proposed microrobot has a thrust force of about two to three orders of magnitude higher than that of microorganisms, such as algae and bacteria, which is sufficient for navigation inside vascular capillaries with blood flow.