A Low-Profile Shear Force Sensor for Wearable Applications

The design, fabrication, and characterization of a low profile shear-force sensor for gait analysis is presented. An analytical model is used to estimate the behavior of the sensor. The sensor response is linear within the modeled range and has a predicted sensitivity of 0.012 pF/N, which is confirmed using a 3D FEM model of the electrical properties of the sensor. The capacitive sensor has a measured sensitivity of 0.0006 pF/N (x-axis) and 0.0003 pF/N (y-axis). When considering the readout electronics, this translates to a voltage/force sensitivity of 9.8 mV/N (x-axis) and 5.2 mV/N (y-axis). The range of the sensor was found to be more than 24 N. The 3D printed sensor is cylindrical with a footprint of ~3 cm² and a height of just 3.6 mm, making it suitable for in-sole shear-force measurements.