Direct Laser Writing of Multishaped VO₂ Microactuators Based on Freestanding VO₂ Film

Abstract

Microactuators that convert external stimuli such as heat, light, current, and magnetic field into mechanical motion are essential components in microelectro‐mechanical systems. To date, microactuators have been fabricated mainly using conventional microfabrication technologies and inorganic thin films, but although such technologies facilitate the mass production of microdevices, they are expensive and lack flexibility when either preparing only a few devices or facing special needs. Laser‐direct‐writing is an effective complement to microfabrication, but is seldom used in the construction of inorganic microactuators. In this work, a laser‐direct‐writing technique on the freestanding vanadium dioxide (VO2) film for fabricating microactuators with arbitrary shapes is developed. The precision of the laser direct writing attained 2 µm under ultralow pulse energy of 52 pJ. The pulse energy is two orders of magnitude lower than that needed for patterning VO2 film and other semiconductor materials on substrates. The overall performance of the resulting VO2 microactuators is comparable with that of those fabricated by conventional microfabrication technologies, but the fabricating efficiency and flexibility are increased. Such a fabrication strategy can also be used to fabricate other smart microdevices, such as strain sensors and photodetectors.

Recent Advances of VO2 in Sensors and Actuators

“…The electrical power applied to structures to ensure the switches was up to an order of magnitude different between the considered studies. Some studies, such as [ 83 ], showed similar deformations regardless of the actuation type. However, in others, for example in [ 80 ], the displacement due to electrical heating was almost ten times smaller than the displacement due to global heating.…”

“…Good performance was achieved in [ 84 ] by integrating a resistance sensor into the structure itself, which allowed for self-sensing of the actual actuator deformation and using a PID controller to more precisely control the actuator deflection. The highest deformation of 75% [ 83 ] and 60% [ 82 ] corresponded to the smaller devices. In both studies, the devices had a bent shape with a relatively high curvature and flattened, fully or partially, when voltage was applied.…”

“…Direct laser writing was used in [83] to produce a microactuator. To achieve this, a VO2 film was laser patterned, then the achieved microbelt structure was detached from Two actuation methods were proposed for the actuator: electrical or light actuation.…”

“…The information about the sizes and displacements of the considered structures were compiled as Figure 11. (Cabrera, 2014) [81], [82], [83], and (Merced, 2015) [84].…”

“…Two longer devices showed a moderate displacement of 23% [81] and 18% [84]. Good performance was achieved in [84] by integrating a resistance sensor into the structure itself, (Cabrera, 2014) [81], [82], [83], and (Merced, 2015) [84].…”