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.

Review of the Applications of Micro/Nanorobots in Biomedicine

“…Besides, an acoustic levitation module was installed to suspend the microrobots in the fluid, and an electromagnetic coil system was set up to drive them. 192 In addition, computer-designed algorithms can be utilized to control the swarm motion of microrobots. The particle swarm optimization algorithm designed by Villa et al has the advantages of fewer parameter adjustments and less memory usage.…”

“…(h) Schematic illustration of magnetic helical microrobot’s lateral drift reduction via acoustic levitation. Reproduced with permission from ref . Copyright 2020 AIP Publishing.…”

“…As shown in Figure (h), Xu et al proposed a reliable propulsion method by applying a sound field to suspend the microrobot on the substrate to reduce unwanted lateral drift. Besides, an acoustic levitation module was installed to suspend the microrobots in the fluid, and an electromagnetic coil system was set up to drive them …”

Micro/Nanorobots for Medical Diagnosis and Disease Treatment

“…In addition, the magnetic field can also control the movement of micro/nanorobots, together with other physical fields. Xu et al [ 31 ] proposed a reliable propulsion method to reduce excess lateral drift during the entire motion by applying ultrasonic waves to the substrate, which is a novel and effective strategy to further improve motion control, as long as an electromagnetic coil system is established to drive the spiral robot.…”

Recent progress in magnetic applications for micro- and nanorobots

“…Therefore, research on MNRs has become the pursuit of many researchers [5]. In recent years, a variety of driving methods for MNRs have been proposed, such as light [6][7][8][9], acoustics [10][11][12], magnetic fields [13][14][15][16][17][18][19][20], self-electrophoresis and self-thermophoresis, bubbles, and many other forms [21]. As a biofriendly approach, the penetration of biological tissues without damage and free movement in the microbial environment can be achieved with magnetic fields, which has become a highlight of research in the field of MNRs.…”