A 8 mm, 0.26 gram motor has also been developed that can provide 0.054 N-cm of torque 2 . Piezoelectric rotary motors are also available commercially from Shinsei and Canon. One possible actuator design with a piezoelectric rotary motor is shown in figure 4 . The motor winds a spring up. The other end of the spring is held by a pin.
All insulators are electrostrictive and produce a strain under an applied electric field.
Magnetostrictive Actuators Like the Piezoelectric effect where the material deforms under an applied electric filed, a magnetostrictive material deforms in a magnetic field. Induced strains and maximum stresses are on the same order of magnitude as piezoelectrics. One major disadvantage of magnetostrictive actuators is the need for a device to produce the magnetic fields. This device is typically a coil wrapped around the material. This makes the device bulky and losses in the coils can be high.