Abstract

We describe a new approach for the parallel reading of the dynamical response of micromechanical oscillators in array using an interferential imaging method coupled to a multichannel lock-in detection. The mechanical responses and the resonance frequencies of each oscillator are deduced from the images of their oscillation amplitude and phase versus the excitation frequency. The goal is the detection of femtogram mass changes through the measurement of induced resonance frequency changes between loaded oscillators and reference oscillators. A measurement of the phase change for a frequency close to the resonance frequency f is a sensitive and reliable method to determine the frequency shift Δf. In this study bare and gold-covered SiO₂ cantilevers have been used as oscillators and a phase measurement sensitivity of 10^-3 rd has been achieved. Such a value is equivalent to a sensor mass change sensitivity better than 100 femtograms. The fields of application extend from DNA microchips to environmental sensors.

© 2001 OSA/SPIE