Sensitivity enhancement of a resonant mass sensor based on internal resonance

There exist numerous vibration modes in a resonant structure, and these modes can interact with each other. Here, the internal resonance between the fundamental mode and higher order modes is observed in a polyvinylidene fluoride piezoelectric membrane as a resonant mass sensor. Higher order modes draw energy from the fundamental one and vibrate at integer times of the fundamental mode's frequency. The resonance frequency shift of the fundamental mode can thus be magnified integer times through internal resonance. The sensitivity of the resonant mass sensor, defined by the resonance frequency shift caused by mass change, is enhanced based on this mechanism. The sensing characteristics are experimentally studied with a concentrated mass load attached to the sensor. The sensitivity improvement of directly using higher order modes and detecting the internal resonance response is tested and compared in our experiment. An 11 times sensitivity magnification is achieved with the internal resonance method, which has an obvious advantage over the higher order method.