Ferromagnetism can offer strong magnetic interaction as the fundamental working principle in a wide range of magnetic actuating applications. This dissertation demonstrates the design, fabrication, and testing of three types of untethered insect-scale robots by using soft and hard ferromagnetic materials, including robust crawling robots on the solid ground, fast-moving swimming robots in the liquid, and the smallest untethered flying robots in the air. Specifically, untethered soft crawling robots of 11 mm in length driven by magnetic anisotropy are designed and constructed by a molding process using self-assembled iron filing mesh as the soft ferromagnetic material. By applying an external alternating magnetic field at the resonant frequency of the robot, untethered crawling movements are realized with a speed of ~0.19 cm/s at 2.5 Hz and 46 mT. The soft crawling robot is robust to be still functional after being crushed by a car.
An insect-scale swimming robot with a weight of 46 mg is fabricated by a 3D printing process and equipped with two permanent hard magnets of NdFeB. A single axis alternating magnetic system is utilized as the external powering source for controllable mobility and stability in water to achieve a vertical moving speed of 19.1 body length per second and perform key maneuvering functions such as upwards, downwards and stationary motions as well as designated movements toward targeted locations.
The single-axis driving mechanism is then used to power untethered insect-scale flying robots of 9.4 mm in the wingspan size in the air with self-stabilized and navigable aerial travels as compared to state-of-art works of flying robots in similar sizes, including hovering, turning, object hitting, and collision survivability. Furthermore, by adding an infrared detecting sensor to a 110-mg flying robot, the system can perform environmental light survey during an untethered flight. The wireless drive mechanism, system operation principle, and flight characteristics can be optimized for further advancements and miniaturizations toward practical applications
