Magnetic-based motion control of sperm-shaped microrobots using weak oscillating magnetic fields

We experimentally demonstrate that using oscillating weak magnetic fields a sperm-shaped microrobot (which we refer to as MagnetoSperm) can swim using flagellar propulsion and slide on a surface under water. The sperm morphology allows the MagnetoSperm to mimic the locomotion mechanism of a living sperm cell. The MagnetoSperm is designed and developed with a magnetic head and a flexible tail to provide a magnetic dipole moment and propulsion, respectively. The head oscillates under the influence of controlled oscillating weak magnetic fields (∼5 mT). This oscillation generates a thrust force in the flexible tail, and hence allows the MagnetoSperm to overcome the drag and friction forces during swimming and sliding on a surface, respectively. Point-to-point open- and closed-loop control of the MagnetoSperm are accomplished using an electromagnetic system under microscopic guidance. This motion control is done in two cases, i.e., swimming in water and sliding on a surface. At oscillating magnetic field of 5 Hz and 45 Hz, the MagnetoSperm swims at an average swimming speed of 32 μm/s (0.1 body lengths per second) and 158 μm/s (0.5 body lengths per second), respectively. At the same frequencies, the MagnetoSperm slides on the bottom of a petri-dish at an average speed of 21 μm/s (0.07 body lengths per second) and 6 μm/s (0.02 body lengths per second), respectively.