Multifunctional Electronic Devices Based on Conductive Natural Materials

Abstract

The demand for stretchable and flexible multifunctional electronic devices, based on conductive nanomaterials, is rapidly increasing due to their interesting applications as human body movement detection, robotics, human-machine interface, and heaters. There still exists a great challenge to manufacture these devices through a scalable, cost effective and environmentally friendly fabrication methods and materials. In this Ph.D. research, the development of multifunctional electronic devices based on biodegradable natural materials and carbon particles (graphene nanoplatelets (GNPs) and carbon black (CB)) through simple and mass-producible methods of coating is presented. In particular, the coating technique to reach highly conductive yarns or fabrics is one of the main goals. For this purpose, various coating techniques, including electrophoretic deposition (EPD), a new coating technique based on ultrasonication, spray coating, and stirring technique were utilised to obtain highly conductive natural materials. A systematic study on the enhancement of electrical conductivity of natural fibre yarns/fabrics was conducted with consideration of the most effective parameters in each coating technique. Various chemical characterisations and morphology study were also used to support the obtained results. Conductive natural materials in the form of yarns or fabrics were then incorporated into a highly stretchable elastomer (Ecoflex) to be utilised as strain sensors and heating devices. The electromechanical characterisations for the developed devices showed their outstanding sensing performance with high stretchability and high sensitivity (gauge factors up to about 102,000) for monitoring various human body movements, sound signal recognition, and sensitive pressure sensors with high durability and fast response time. Furthermore, the electrothermal characteristics of the developed devices exhibited their excellent performance, working at high temperatures (approximately 240 °C) with low input power. Considering the advantages including simple fabrication processes, cost-effectiveness and environmental friendliness for the developed lightweight multifunctional devices, it can be said that they can have potential applications in green electronic devices, healthcare, and human-machine interaction platforms (e.g. gaming).