Printed Piezoresistive Strain sensors for Wearable Systems

Printed strain sensors are on high demand for flexible electronics and smart wearables. They are expected to exhibit high Figure of merits in terms of sensitivity, reliability, cost effectiveness, ease of fabrication etc. However, it is challenging to meet these attributes simultaneously. In this paper, we present a simple yet efficient method to fabricate the printed piezoresistive strain sensors with composite of carbon-based and silver-based pastes. The composite paste containing 80% and 20% by volume of carbon and silver paste was printed on poly vinyl chloride (PVC) substrate to realize the piezoresistive strain sensor over an area of 20 mm x 2 mm. The electromechanical characterization of the sensor demonstrated sensitivity of the order of 80% ($\Delta$R/R) with good repeatability and stability. The piezoresistive behaviour of presented printed composite material is owing to the modulation of electrical conductivity and conduction path by the minor inclusion of highly conductive silver fillers in a slightly less conductive carbon matrix. Finally, the strain sensor was integrated on the finger of a vinyl glove and response was monitored with finger movements. The obtained results point towards the potential use of the sensor for flexible electronics, robotics and smart wearable devices.