1 Bioprobes, Department of Micro- and Nanotechnology, Technical University of Denmark2 Department of Micro- and Nanotechnology, Technical University of Denmark3 MicroNano Tribology and Modeling, Department of Micro- and Nanotechnology, Technical University of Denmark4 Center for Individual Nanoparticle Functionality, Center, Technical University of Denmark5 Experimental Surface and Nanomaterials Physics, Department of Physics, Technical University of Denmark6 Center for Intelligent Drug Delivery and Sensing Using Microcontainers and Nanomechanics, Center, Technical University of Denmark
We present a method for microcantilever resonant frequency detection. We measure the direct current from an intermittent contact once every vibration cycle between the conducting cantilever and a counterelectrode at a low bias voltage with respect to the cantilever, while the excitation frequency and amplitude are varied. The result is an almost "digital" detection of the resonant frequency. A relative frequency resolution Delta f/f of 1/80 000 with high signal to noise ratio in ambient conditions is demonstrated. The detection method can be applied to portable sensor systems with very high frequency nanoelectromechanical cantilevers using simple off-chip electronics.