Optical scanner based on a NiMnGa thin film microactuator

An optical scanner of 9 $\times$ 3 $\times$ 5 mm$^3$ size is presented, which is driven by a microactuator of Ni$_2$MnGa. The microactuator is fabricated by magnetron sputtering of a Ni$_2$MnGa thin film and subsequent photochemical micromachining. For operation of the scanner, a novel mechanism is proposed, which is based on the antagonism of magnetic and shape recovery forces. Thus, large bending forces in both actuation directions and low biasing forces can be generated simultaneously in a single microdevice. This mechanism is used to realize a large scanning angle of 50 deg. The dynamics of motion is characterized by heat-transfer times. Typical heating and cooling time constants are 2 and 16 ms, respectively. Below a critical frequency of about 55 Hz, the scanning angle is independent of the actuation frequency