Paddling Mechanisms of Water-Beetle Type Magnetic Micromachines

Two kinds of swimming microrobots, which imitate the propulsive mechanisms of water beetles, have been developed for amusement use. Each of them includes one or two magnets and a propulsive mechanism composed of two legs with paddles. When alternating magnetic fields are applied, the magnet oscillates angularly due to magnetic torque and drives the propulsive mechanism. The relation between thrust and angle of the power stroke was first examined using a simple model swimming in the direction of the magnetic field. As a result, we found that the movable area of the legs should be confined to the hind half of the body. Based on this result, we fabricated a second model that swims in the direction perpendicular to the magnetic field. When alternating magnetic fields of 2. 4 kA/m at 3-10 Hz were applied using the coil wound around the water tank, the second model successfully swam at a speed of several cm/s and showed lifelike behavior.