Purely viscous acoustic propulsion of bimetallic rods

Synthetic microswimmers offer models for cell motility and their tunability makes them promising candidates biomedical applications. Here we measure the acoustic propulsion of bimetallic micro-rods that, when trapped at nodal plane a MHz resonator, swim with speeds up to 300 microns per second. While past streaming predict that are more than one order magnitude smaller our measurements, demonstrate locomotion rods is driven by viscous, non-reciprocal mechanism relying on shape anisotropy akin used swimming cells reproduces data no adjustable parameters.