When a piece of a material called T erfenol-D is placed near a magnet, this special rare-earth-iron material will change its shape slightly. This phenomenon, called magneto striction effect, is used to make linear motors with micro-inch displacement capabilities. To run the actuator , a magnetostrictive rod, covered by a magnetic coil, is attached to two chassis . As the magnetic field changes, causing the rod to contract and expand, one chassis moves relative to the other. A similar concept is used with piezo crystal to create a linear motor with nano-inch displacements, including flexible actuators for robots.