Effect of carbon nanofiber on compressive piezoresponsive properties of polymer nanocomposites

Abstract

The compressive piezoresponse is the response of a material against applied pressure, mostly in terms of converting the compressive mechanical energy to resistance (Piezoresistive) and electrical energy (Piezoelectric). This investigation focuses on the Compressive Piezoresponsive sensing mechanism for bio-sensing application of gait monitoring utilizing the ground contact force of foot strike data. Though metals and ceramics dominate in this field, wearable application is limited by their lack of compression and flexural properties. Some of them like lead based compounds also have toxicity issues on skin contact. Polymers have the potential to overcome these limitations. They are good candidates as new developing sensors and thus they are emerging in the field of piezo bio-sensor applications and in health monitoring applications. The piezoresponsive properties of polymers can be enhanced in its nanocomposite form to match its performance to commercial metal and semiconductor sensors used in this field. Carbon nanofiber (CNF) is an affordable conducting nanomaterial which can improve the electrical conductivity of polymers as well as the piezoresistive and piezoelectric responses of a polymer. The CNF has high mechanical strength and electrical conductivity. CNF composites are applied in many fields such as electrical devices, batteries, super capacitors and sensors to enhance the current and voltage responses in polymers. In this study, the effect of CNF on piezoresistive property of Thermoplastic polyurethane (TPU) and piezoelectric property of synthetic (Polyvinylidene fluoride (PVDF)) and natural (Silk fibroin (SF)) polymers has been researched. CNF significantly improves the electrical conductivity of TPU making it suitable for compressive piezoresistive applications. It also builds a staggered conducting path to facilitate easy transfer of charge and thereby, enhances the piezoelectric newline