Piezoresistive Sensors Fabricated with Conductive Textiles for Monitoring the Step Rate with Read-Out Electronics and Wireless Connection to a Smart Watch

Soft sensors made with conductive smart textiles have been developed for connecting with the environment, increasing operator safety, entertainment and physiological parameter monitoring. This paper describes the fabrication processes for smart textiles with conductive fibers made with different types of metal filaments and explains the design choice for pressure measurements with soft sensors. This new type of materials is investigated for the design of a removable insole sensor for step rate monitoring. The main components integrated into the wearable device are a piezoresistive sensor, a low power analog front-end and a wireless connection with a smart watch device. The dynamic behavior of the piezoresistive is characterized and the output voltage waveform is processed to estimate the step rate per second. The advantage of a customize graphical user interface on the display of the smart watch allowed easy monitoring of the step rate from theaverage pressure variation on the sensorized insole during walking and running. The paper demonstrates that this sensor technology can be used to design different types of piezoresistive sensors with multiple elements to record dynamically the spatial distribution of foot pressure.