A Miniature Flexible-Link Magnetic Swimming Robot with Two Vibration Modes: Design, Modeling and Characterization

In this letter, we report a miniature swimming robot that consists of a nonmagnetic V-shaped head, an I-shaped tail attached with a magnet and a flexible link for interconnection of the rigid head and tail. The use of a flexible link enables the robot to exhibit two different vibration modes by tuning the input frequencies of the applied oscillating magnetic field with uniform field strength. When the input frequency is below 15 Hz, the head and tail show similar and large vibration amplitudes, and the net centrifugal force mainly contributes to the forward propulsion of the robot in fluid. While with high input frequencies (i.e., larger than 30 Hz), the flexible link can filter away high-frequency signals to efficiently avoid the passive vibration of the nonmagnetic head. Simultaneously, the magnetic tail vibrates with relatively large amplitude and generates forward propulsion force for the robot. To understand the whole-body-vibration and tail-vibration behaviors, an analytical model has been developed. Moreover, swimming performances of this robot, i.e., the propulsion force and swimming velocity, are characterized on the substrate-water interface. Finally, we demonstrate two-dimensional manipulation of tiny objects by utilizing the two vibration modes of the robot.