Steering magnetic micropropellers along independent trajectories

Multi-microrobot control is highly promising for the assembly of matter on the microscale, in situ sensing, targeted drug delivery or nanosurgery. Magnetic micropropellers can be powered and steered by external magnetic fields and therefore represent a promising microrobotic actuation mechanism. However, the simultaneous actuation of multiple propellers along independent trajectories has yet to be realized. This is challenging, specifically because all propellers are steered by the same fields. We identify here an optimal control strategy based on a thorough theoretical analysis of multi-microrobot control. Based on analytical results and simulations, we estimate the limitations to the achievable control precisions due to diffusion, errors in the field application, and interactions between propellers. We find that control precisions of a few micrometers might be achievable.