Test and fabrication of piezoresistive sensors for contact pressure measurement

The use of contact pressure sensors has become popular in various engineering disciplines in recent years. They are used in characterization of vehicle tires, bearings, wind tunnels, prosthesis design, ergonomic analysis among other areas. These sensors are fabricated with materials that have certain properties such as piezoelectricity, piezoresistance and variable capacitance; however, the most used characteristic is the piezoresistive effect. This paper describes the fabrication of three different sensors using piezoresistive materials. Furthermore, a comparative technical study including a commercial sensor as a benchmark is done with the aim of selecting a suitable material when measuring contact pressure. The repeatability and hysteresis of each sensor were evaluated in a response to load test realized several times. A time drift test with a dead load was also performed for evaluating stability. Materials such as piezoresistive fabric or ink show to be suitable for applications where deformation and flexible sensors are required, Velostat is the least accurate but suitable for basic applications and in which a high resolution is not needed. Finally, some recommendations are given regarding the type of material to be used in pressure sensors for engineering applications, particularly in the biomedical field.