Photothermal actuation of VO2:Cr-coated microcantilevers in air and aqueous media

A silicon cantilever coated with a Cr-doped vanadium dioxide (VO2) thin film was photothermally actuated with a red pulsed laser in order to study its dynamic performance in air and in water. Very high cantilever vibration amplitudes were obtained in air (similar to 46.8 mu m) up to 500 Hz, while in water a decrease in amplitude was observed from the starting pulse frequency of 1 Hz with relatively high amplitudes (-3 dB) up to similar to 10 Hz. Although fluid drag was found to have no effect on the cantilever response through the measured frequency range in either media, numerical simulations show that heat dissipation through the anchor and the surrounding fluid was the cause of the amplitude reduction observed. These results suggest the use of Cr-doped VO2-coated cantilevers as optically driven actuators with high deflections in liquid media.