Resonating Silicon Beam Force Sensor

A resonating silicon-beam force sensor is being developed using micromachining of silicon and IC-compatible processes. Results are reported here of measurements on the force-to-frequency transfer of bare silicon prototypes. The measurements with forces on the sensor beam up to 0.4 N show a frequency shift of 3.1 to 5.2 times the unloaded resonance frequency f. (fo = 3 to 5 kHz), depending on the exact dimensions. Considering these figures, we can predict a frequency shift of 18.3 to 27.6 kHz at the maximum load of 1.0 N for the measured samples. Due to the sample lay-out, a force transfer is present from the externally applied force to the actual pulling force on the sensor beam. Using a simple model to calculate this reduction, we obtain good agreement between the measurements and predictions.