Design of Microscale Magnetic Tumbling Robots for Locomotion in Multiple Environments and Complex Terrains

This paper presents several variations of a microscale magnetic tumbling (TUM) robot capable of traversing complex terrains in dry and wet environments. The robot is fabricated by photolithography techniques and consists of a polymeric body with two sections with embedded magnetic particles aligned at the ends and a middle nonmagnetic bridge section. The robot's footprint dimensions are 400 m x 800 m. Different end geometries are used to test the optimal conditions for low adhesion and increased dynamic response to an actuating external rotating magnetic field. When subjected to a magnetic field as low as 7 mT in dry conditions, this magnetic microrobot is able to operate with a tumbling locomotion mode and translate with speeds of over 60 body lengths/s (48 mm/s) in dry environments and up to 17 body lengths/s (13.6 mm/s) in wet environments. Two different tumbling modes were observed and depend on the alignment of the magnetic particles. A technique was devised to measure the magnetic particle alignment angle relative to the robot's geometry. Rotational frequency limits were observed experimentally, becoming more prohibitive as environment viscosity increases. The TUM's performance was studied when traversing inclined planes (up to 60 degrees), showing promising climbing capabilities in both dry and wet conditions. Maximum open loop straight-line trajectory errors of less than 4% and 2% of the traversal distance in the vertical and horizontal directions, respectively, for the TUM were observed. Full directional control of TUM was demonstrated through the traversal of a P-shaped trajectory. Additionally, successful locomotion of the optimized TUM design over complex terrains was also achieved. By implementing machine vision control and/or embedding of payloads in the middle section of the robot, it is possible in the future to upgrade the current design with computer-optimized mobility through multiple environments and the ability to perform drug delivery tasks for biomedical applications.