Selective High-Frequency Mechanical Actuation Driven by the VO2 Electronic Instability

Relaxation oscillators consist of periodic variations of a physical quantity triggered by a static excitation. They are a typical consequence of nonlinear dynamics and can be observed in a variety of systems. VO₂ is a correlated oxide with a solid-state phase transition above room temperature, where both electrical resistance and lattice parameters undergo a drastic change in a narrow temperature range. This strong nonlinear response allows to realize spontaneous electrical oscillations in the megahertz range under a DC voltage bias. These electrical oscillations are employed to set into mechanical resonance a microstructure without the need of any active electronics, with small power consumption and with the possibility to selectively excite specific flexural modes by tuning the value of the DC electrical bias in a range of few hundreds of millivolts. This actuation method is robust and flexible and can be implemented in a variety of autonomous DC-powered devices.

High-frequency mechanical actuation of a microelectromechanical system (MEMS) device from a DC electrical bias is achieved by employing VO₂, a material exhibiting a combined electrical and structural phase transition at 65 °C. The DC bias triggers spontaneous and repetitive phase transitions on a micrometric region that works as engine to power the movement of the MEMS around its mechanical resonances.

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