Drastic and Fast Changes in Stress/Strain of Photothermally Actuated VO₂-Coated Microcantilevers

The time-dependent response of a 300 μm-long VO₂-coated silicon micro-cantilevers photothermally driven over the film’s insulator-to-metal transition (IMT) by laser light pulses was studied and tip displacements of ∼ 80 μm were found for driving frequencies over 100 Hz, while displacements of ∼ 10 μm were found for frequencies close to 1.2 kHz, with no performance degradation after millions of pulses. Additionally, the deflection of a 250 μm-long VO₂-coated silicon micro-cantilever as a function of temperature heated through a Peltier heater was studied. The main mechanism limiting amplitude was found to be the time required for heat transport during heating and cooling. Hence, wireless actuation in this manner is expected to be even faster for smaller cantilevers.