Measurement of the Resonant Frequency of Nano-Scale Cantilevers by Hard Contact Readout

It is shown that detection of the resonant frequency of a nano-scale cantilever is possible by measuring the time average current flowing from an electrode to the cantilever during hard contact occurring twice every cycle of the cantilever vibration. The electronic detection method is insensitive to unavoidable stray capacitances in the system and provides very high resolution using simple low bandwidth off-chip electronics. Moreover, the detection method does not suffer from the common problem in electronic detection methods, where the strong actuation signals often contaminate the detected signal. The readout method is thereby ideally suited for portable sensor systems.