Smart material yields programmable tilting micro mirror
VO2 undergoes a temperature-driven metal-insulator transition near room temperature with a concomitant change in crystal symmetry – the so-called Mott transition. The partnership was able to use VO2 thin films create complex mirror support structures to create a programmable tilting mirror.
The nature of such transition-metal oxides is that they require little energy to drive the transition and less than more conventional actuation technologies.
The present VO2-based MEMS mirror device is operated electrothermally through integrated resistive heaters, and the behavior is characterized across the VO2 phase transition, which occurs at a temperature of ~68 degrees C and spans about 10 degrees C.
The maximum vertical displacement of the mirror platform is 75micron and it occurs for an input voltage of 1.1V. This translates to an average power consumption of 6.5mW per mirror actuator and a total power consumption of 26.1mW for the entire device. The studies included in this paper are key for future device improvements and further development of MEMS mirror actuation technology, which could include the use of the hysteresis of VO2 for programming tilting angles in MEMS mirrors.
During testing the Mott-MEMS mirror showed vertical movements and tilt angles of 75 micrometers and 5.5 degrees, respectively. The material displayed hysteretic behaviour, meaning the response to force or stimuli was dependent on the previous response. Going forward the researchers can predict how the device will react to certain electrical signals and they can “program” the devices for specific responses.
“The actuation of such devices using smart phase-change materials represents a new operating principle that enables their programming and reduces power consumption,” said Nelson Sepulveda, a professor of electrical and computer engineering at Michigan State University, in a statement issued by Wright-Patterson Air Force Base.
Moving forward, the research will focus on developing programmable MEMs mirrors and improving the device design to allow for better device control and larger movements. The team is also investigating VO2 for use in variable optical attenuators.
www.wpafb.af.mil
www.msu.edu
Paper in Journal of Microelectromechanical Systems
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