A kind of novel reflective grating microcantilever based on SOI was designed and fabricated for biosensing. For
measuring the extremely low deflections of the microcantilever, a high precision optical readout approach based on
diffraction spectrum balancing feedback control was presented. The read out system include a PI M-038 precision
motorized rotation stage, a CCD, a 650 nm laser, a fiber, a min fiber GRIN collimator and lens. The practical
measurement resolution of the system is up to 1x10-4 deg, that is to say, for a length of 250um microcantilever, the tip
measure resolution is up to 0.043nm.
Microcantilever as state-of-art sensor platforms has been widely investigated. Optical Fiber biosensors have the potential
to provide cost-effective, real time, continuous, in situ measurements. The micro cantilever was fabricated on single
crystalline SOI wafer using a series of side definitions and backside wet/dry etchings. Since the micro cantilevers are to
be used as biosensor, 50 nm Au layer was deposited for the immobilized of bimolecular on the cantilever surface and for
reflecting the beam of light back into the fiber, the different light intensities means different bimolecular concentrations.
The lamp-house is 1310 nm super luminescent LED. Single mode fiber with gradient index lens as a collimator and 3dB
50:50 optical coupler was used to transmit light. PINFET was used to convert the reflecting the light intensities into
electronic signal. The test results demonstrated that the optical fiber reflective read out microcantilever biosensor has
high sensitivity, high dynamic response, a greatly reduced size and high precision.