Enhanced Sensitivity of Mass Detection Using the First Torsional Mode of Microcantilevers

Using higher resonant modes of microcantilevers promises higher sensitivity in the bio/chemical molecular detection. Compared with the first flexure modes, the first torsional mode can provide an improved mass-sensing resolution due to the higher quality factor. For the accurate characterization of the torsional mode and further detection of the multi-mass attached to the microcantilevers, models based on the Rayleigh-Ritz method, considering the attaching positions of the micro and nano objects adhered to the microcantilevers is developed. An ragweed pollen, as target mass are located on different positions on a commercial microcantilever for the contrastive experiments of the first and second flexure and the first torsional resonances in the air. From experimental vibration spectrums of the "cantilever-object" system, we can get that the mass sensitivity of the torsional mode is an order higher than the conventionally used the first flexural mode. The torsional mode can offer significantly enhanced mass sensitivity within the realm of existing microcantilever technology.