Enhanced sensitivity of mass detection using the first torsional mode of microcantilevers

Compared with the first flexure mode, higher resonant modes of the microcantilever-based mass sensor promise enhanced sensitivities in bio/chemical mass detection due to higher quality factors. Therefore, the first torsional mode is employed in our research for improved resolution of mass detection. Aiming at accurate characterization of the first torsional mode and further detection of the multi-mass attached to the microcantilevers, a model based on the Rayleigh–Ritz method, considering the attaching positions of the micro/nanoobjects adhered to the microcantilever, is presented. A ragweed pollen, as a target mass, was located at different positions on a commercial microcantilever for the contrasting experiments of the first and second flexures and the first torsional modes of the 'cantilever–object' system in air. Experimental results show that the mass sensitivity of the first torsional mode is an order higher than that of the first bending mode within the realm of existing commercial microcantilevers. The proposed model was further validated by the multi-mass detection results