Acoustic levitation applied for reducing undesired lateral drift of magnetic helical microrobots

Abstract

Magnetic helical microrobots can be effectively propelled via a controlled rotating magnetic field, and they have shown great potential in various biomedical applications. However, lateral drift caused by fluidic drag imbalance makes it hard for microrobots to achieve precise directional motion control, limiting their applications to perform practical tasks. Herein, we propose a reliable propulsion method to reduce the undesired lateral drift through levitating the microrobots from the substrate with the application of an acoustic field. We correlate the lateral drift with the total drag in the horizontal direction, which is mainly determined by the distance between the microrobots and the bottom. Theoretical analysis and simulation results suggest that a higher position from the substrate leads to a smaller lateral drift. We set up an acoustic levitation module to levitate the microrobots in fluids and an electromagnetic coil system to drive them. Experiments with and without acoustic levitation were carried out in contrast to analyze the lateral drift in motion under magnetic actuation. The results show that acoustic levitation can significantly reduce the undesired lateral drift of the helical microrobots, which would be a novel and effective strategy for further improving motion control.