Wheatstone bridge piezoresistive sensing for bulk-mode micromechanical resonator

A balanced wheatstone bridge technique for piezoresistive detection in micromechanical resonators is demonstrated. Two identical beam resonators, which vibrate in the length extensional mode with 180^° phase shift, are connected in serial to compose a wheatstone bridge. With the differential actuation configuration, this approach eliminates the capacitive feedthrough signal, which may heavily bury the piezoresistive signal of the resonator in traditional piezoresistive sensing approach. The proposed technique is experimentally validated. Experimental results show that the capacitive signal embedded in the piezoresistive sensing approach is nearly eliminated. This method provides an effective way for purely piezoresistive sensing of micromechanical resonators.