On the Utilization of the Escape Phenomenon to Realize New Mass Detectors

In this work, we demonstrate the concept of a new type of mass sensor detector. The detector is designed to act as a switch that is triggered if the measured mass exceeds a threshold value. The basic idea of the proposed switch is based on utilizing the escape phenomenon that the nonlinear electrostatic force introduces to the dynamics of a capacitive microcantilever. The detector is excited electrostatically with a frequency near the primary or the sub-harmonics (twice the natural frequency) resonances a way from the instability frequency band (escape phenomenon). By absorbing a threshold mass of a target material, the natural frequency of the cantilever will change in a way that it starts to oscillate in the unstable zone and hence hits the substrate. This action could be utilized to activate, for example, an alarming system indicating that the measured material has exceeded the allowable threshold mass (concentration) value.