Resonating cantilever-based microbiochemical sensors usually consist of a vibration actuating system and a vibration detecting system, which complicates the sensor design and fabrication. We present a new idea for testing the cantilever's vibration without an exclusive detector. The amplitude of vibration can be detected by measuring the third harmonic of the actuating current, and the cantilever's resonance frequency can be consequently obtained. The change of the resonance frequency provides information about the biochemical reaction, which alters the mass of the cantilever and its natural frequency. A system model based on the idea is established and an approximate solution is given. The relation between the vibration state and the third harmonic is discussed, and a corresponding simulation is performed. The system sensitivity is evaluated. Both theoretical and simulation results show that the amplitude of the third harmonic of the actuating current can be used as a criterion to determine the cantilever's vibration state. The idea promises a simpler mechanical structure, thus a cheaper sensor. Sensors based on this idea would also be robust to atrocious environments because the material of the cantilever can be chosen from a wide range.
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