Optical MEMS chemical sensor array

A method for sensing a change in mass of a microbridge in a sensor, comprising the steps of:

• applying a continuous wave laser beam with a continuous wave laser to the microbridge, the microbridge being excited into resonance at its natural frequency by the continuous wave laser beam;
• receiving optical energy at a wavelength close to a resonant wavelength of a Fabry-Perot microcavity, the Fabry-Perot microcavity formed by etching a movable reflective minor into a region of the microbridge and by etching a fixed reflective mirror in a region spaced apart from the microbridge, wherein the fixed reflective minor is fixed to a substrate and the two minors are interconnected by an optical waveguide;
• the movable reflective mirror and fixed reflective minor reflecting optical energy to a receiver;
• interferometrically determining a change in reflectivity of the Fabry-Perot microcavity, the change in reflectivity indicating a change in resonant frequency of the microbridge due to increased mass of the microbridge resulting from sorption of a target chemical by a layer of chemoselective material disposed on the microbridge;
• and
• varying at least one of:
• the continuous wave laser power or the laser wavelength, wherein the laser power and wavelength modify a laser induced optical force acting on the microbridge, and wherein the optical force modifies a mechanical Q-factor of the microbridge.