Continuously tuning the resonant characteristics of microcantilevers by a laser induced photothermal effect

Abstract

Microcantilever sensors are ultrasensitive devices with miniaturized size and fast responding capability. However, they are generally designed to operate in a very narrow frequency range, which has limited their applications. We present here an all-optical technique that enables efficient actuation and rapid tuning of the vibration behaviors of microcantilevers. In particular, the resonant frequency of a microcantilever beam can be continuously tuned remotely by a laser induced photothermal effect to cover a large range with boosted vibration amplitude, beneficial for improving the detection threshold for force and mass. The underlying principles for photothermal actuation and elastic nonlinearity are discussed in detail. A verification experiment proves its potentials in detecting acoustic waves with frequencies far from the initial resonant frequency of the microcantilever.