Dynamics of VO2:Cr coated microcantilevers in aqueous media

Three silicon micro-cantilevers coated with a Cr-doped vanadium dioxide (VO₂:Cr) thin film were photothermally actuated with a pulsed red laser in order to study its dynamic performance in air and in water. Micro-cantilever vibration amplitudes with a magnitude similar to that of DC operation were obtained in air up to 600 Hz. In water, a decrease in amplitude started at ~100 Hz, but it did not go below -3 dB until a few hundreds of Hz. Deflection transients of all micro-cantilevers were also measured in both media. This revealed that, in water, the deflection response to the laser pulses is greatly hampered by the amount of time required for the micro-cantilevers to heat. However, in air, there was no apparent difference in the transients between heating and cooling. These results suggest the use of VO₂:Cr coated micro-cantilevers as optically driven actuators with large deflections in liquid media suitable for biological based applications.