Synthetic microswimmers offer models for cell motility and their tunability makes them promising candidates for biomedical applications. Here, we measure the acoustic propulsion of bimetallic microrods that, when trapped at the nodal plane of a MHz acoustic resonator, swim with speeds of up to $300\mu \mathrm{m}{\mathrm{s}}^{-1}$. While past acoustic streaming models predict speeds that are more than one order of magnitude smaller than our measurements, we demonstrate that the acoustic locomotion of the rods is driven by a viscous, nonreciprocal mechanism relying on shape anisotropy akin to that used by swimming cells and that reproduces our data with no adjustable parameters.

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• Flow-structure interactions
• Locomotion
• Swimming
• Living matter & active matter
• Self-propelled particles