Steady state physical modelling for optimizing capacitive tactile sensors thermal sensitivity

Capacitive tactile pressure sensors are increasingly used in ergonomic testing and medical devices, specifically for human body measurement and characterising human interactions with their environment, where temperature coefficients are important considerations. New wearable and flexible sensor designs appear regularly in the literature however they rarely discuss why respective designs are improvements over predecessors, or any sensor performance optimisations for their intended applications. This lack of clear design rationale in the literature leads to inefficient design iterations and suboptimal sensor performance as designs are seemingly ‘trial and errored’. This work analytically models the steady state mechanics of a simple commercial-off-the-shelf capacitive tactile sensor, SingleTact™ S15-4.5N, with nominal base temperature sensitivity of 0.2% FSR/°C, using multi-objective optimisation on the critical factors to minimise the temperature coefficient. This work investigates the governing factors for the temperature coefficients via sensitivity analysis on the experimentally validated model, providing novel design insight. By optimizing the design parameters within practical bounds, improvements of 16.16%, 16.47%, and 14.74%, can be achieved for the baseline, sensitivity, and linearity (steady state) temperature coefficients respectively. The model is shown to be useful in determining dominant factors controlling the steady state temperature coefficients as well as estimating sensitivity to manufacturing tolerances. This approach will be used on more complex designs in future to ensure optimal application performance, and assess the impact of manufacturing constraints on sensor performance to the benefit of manufacturers and end users alike