MEMS Force Sensor in a Flexible Substrate Using Nichrome Piezoresistors

MEMS force sensors embedded in flexible polyimide substrates are reported, motivated by the need to monitor force and pressure on nonplanar surfaces for structural health monitoring. Details of the fabrication, measured preliminary results, and figures of merit are described. The sensors showed an average piezoresistive gauge factor of 1.75. The average value of normalized Hooge noise coefficient K_1/f was found to be 1.89×10^-10. The sensitivity was measured to the range from 0.266 to 2.248 V/N with an average sensitivity of 1.25 V/N. The noise equivalent force was calculated to the range from 8.83 to 46.56 μN with an average value of 20.47 μN for the force sensors in a noise frequency bandwidth from 1 to 8 Hz.