A Frequency-Modulated Tripedal Soft Magnetic Robot With Diverse Motion Modalities for Ingestible Applications

Soft robots driven by the external magnetic field can be widely applied in medical areas to realize noninvasive diagnosis and treatment. These robots gain advantages in flexibility, untethered remote control, and safe human interaction. Thus, they can achieve functions such as endo-imaging, drug delivery, and biopsy. However, developing a multi-functional magnetic-driven soft robot to carry out various medical missions remains challenging. In this work, we design a tripedal soft magnetic robot with three radial-magnetized cylindric permanent magnets embedded in three soles. The diverse motion modalities as the prerequisites to realize multi-functionality are explored in this work. The motion generation of the devised robot is investigated by applying an external uniform magnetic field. The motion modalities for movement include butterfly crawling (along the x and y axis), scorpion crawling, and rolling. We develop the different control signals from a three-directional magnetic field in various shapes, frequencies, amplitudes, and offsets for our tripedal soft magnetic robot. At different frequencies, the robot exhibits different behaviors in terms of speed and trajectory under different moving modalities. The motion trajectory of the robot in its designated direction shows a wave-like upward trend. The maximum velocity of the butterfly crawling and scorpion crawling motion at the frequency of 1 Hz is measured to be 5.30 mm/s and 9.06 mm/s. The robot can overcome obstacles such as polyps and wrinkles using the scorpion crawling and rolling mechanisms. Aiming at the potential medical application such as biopsy, we designed the leg raising modality ranging from a low frequency to a high frequency (0.02 Hz, 0.1 Hz, 0.5 Hz) using different control signal profiles (step, cosine, inverse exponential).