Propulsion and Rotation of Microrobot Based on a Force on a Magnetic Material in a Time-Varying Magnetic Field Using a Wireless Power Transfer System

In this article, a microrobot capable of creating propulsion force and receiving electrical energy using a wireless power transfer (WPT) system is proposed. As a source of propulsion and rotation for the microrobot, we use the force and torque of magnetic material in a time-variant magnetic field generated by the transmitting coil of the WPT system, with a specifically designed magnetic material which produced even greater force under the same volume. While microrobot propulsion based on the Lorentz force is closely related to the magnitude of the induced current, because the force of the magnetic material in the proposed design is independent of the induced current, it is more practical for miniaturization of the microrobot. Additionally, the proposed model is able to use the LC resonance frequency, and a magnetic material located in the receiving coil introduces a higher coupling coefficient between the transmitting coil and the receiving coil. These characteristics make the proposed microrobot suitable for powering through a WPT system. The feasibility of the proposed model was initially investigated by theoretical analysis and then verified in simulation and an experiment. In the experiment, the fabricated microrobot 4.5 × 2.0 × 2.0 mm
³
in size achieved a power transfer efficiency rate of 4.5% at 103 kHz with a propulsion speed of 7.5 mm/s and rotating motion.