MEMS cantilever sensor array oscillators: Theory and experiments

This paper demonstrates that an array of cantilever sensors can be operated simultaneously at resonance using a single actuator and a single photodetector. Self-sustained oscillations (SSOs) of cantilevers can be achieved in a feed-back loop using gain saturation mechanism in the electronics. Multiple cantilevers require separate saturation mechanisms and separate sensing electronics for each channel. We introduced optical non-linearity using diffraction gratings at the tip of each cantilever which provide separate saturation non-linearity, enabling a single detector based oscillator array. Two-cantilever SSO operation is investigated analytically, and the multiple frequency oscillation criteria are established. Cross-coupling between the oscillation frequencies has been investigated by using this multi cantilever model. The proposed model will be helpful to design dynamic-mode MEMS (Micro-electro-mechanical systems) cantilever sensor arrays with the desired functionality and cross-talk levels. This multiple SSO operation can be used in conjunction with dense cantilever arrays for various biosensor applications. Moreover, the model can also be useful to understand the operation of any kind of multiple simultaneous oscillator systems, which employs a single feed-back loop. We also present experimental results that confirm our model.