We present a parametric resonance-based mass sensor, comprised of a single-crystal silicon micro-oscillator with sensitivity at the pico-gram (10 -12 g) level when operating in air. This mass sensor detects mass change by measuring frequency shift at the boundary of the first order parametric resonance 'tongue'. High sensitivity is achievable due to the sharp jump in amplitude caused by parametric resonance at predictable drive frequencies. Pt deposition using focused ion beam and water vapor are used to change the mass of the testing oscillator. The results show that the sensitivity can be > 1 order higher than the same oscillator working at simple harmonic resonance mode. The effect of noise on mass sensing ability in this nonlinear dynamic system is considered as well.
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Zhang et al. (2004) studied this question.