Integrated cantilever sensors with a torsional resonance mode for ultraresoluble on-the-spot bio/chemical detection

Torsion-mode resonance is built in an integrated cantilever sensor for ultraresoluble detection of specifically bio/chemical mass adsorption. The superior mass resolution of the torsion-mode cantilever to a conventional bending-mode one is verified by energy-dissipation analysis and Q-factor simulation. With integrated transverse piezoresistance for frequency-shift signal readout and Lorentz force for resonance excitation, the torsion-mode sensor is optimally designed for high sensitivity. The microfabricated torsion-mode sensor is measured with a high close-loop Q factor in air. By Allan-variance analysis for the measured frequency stability, 23 fg resolution is obtained for the torsion-mode sensor, which is much improved compared to the 313 fg for the conventional flexure-mode sensor. The torsional sensor is used to recognize biotin-avidin specific combination, resulting in 443 Hz frequency shift for 50 mu M streptavidin solution. (c) 2007 American Institute of Physics.