Enhanced mass sensing using torsional and lateral resonances in microcantilevers

We present a method to detect, with enhanced sensitivity, a target mass particle attached eccentrically to a microcantilever by measuring multiple three-dimensional modes in the microcantilever vibration spectrum. Peaks in the spectrum reveal a complex coupling between the bending, torsional, and lateral motions and detailed finite element models assist in their interpretation. The mass sensitivities of the torsional and lateral mode frequencies are an order of magnitude greater, and their Q factors significantly higher, than that of the conventionally used fundamental bending mode. These modes offer significantly enhanced mass sensing capabilities within the realm of existing microcantilever technology. (C) 2004 American Institute of Physics.