Sensitivity enhancement of a microcantilever based DC current sensor by using its torsional modes

This paper investigated the current sensitivity of a resonant sensor based on a magnetically actuated piezoresistive microcantilever in different resonant modes, which were the first flexural mode and the first and second torsional modes. The sensor was based on the idea of measuring the electrothermally induced resonance frequency shift as a result of the Joule heating dissipated when the DC current flowed through the Wheatstone bridge on the microcantilever. Two theoretical models between the microcantilever's resonance frequency and the square of the applied DC current for the sensor operating under the flexural and torsional modes were established. From the experimental results, it can be seen that the current sensitivity of the first torsional mode is an order of magnitude greater than the first flexural mode, but less than that of the second torsional mode. In addition, the effect of the DC current's direction on the measured results should be taken into account before detecting the DC current. (paper)