Great new generation carbon microsphere-based composites: Facile synthesis, properties and their application in piezo-electric energy harvesting

In this work, new generation carbon microspheres (CMS) based rubber composites have been obtained for flexible electronics applications such as stretchable piezo-electric energy harvesting devices. The rubber matrix used was room-temperature-vulcanized silicone rubber (RTV-SR). Herein, the CMS was exploited as a source of reinforcement and conductive material for improving mechanical and electrical properties. For example, the compressive modulus was 2.1 MPa (virgin) and increased to as high as 3.3 MPa (5 phr CMS). Similarly, the Shore A hardness was 26 (virgin) and increased to 40 (5 phr CMS). The electrical properties were also influenced significantly with electro-chemical resistance of 22.05 k ohm (virgin) and decreased to 15.91 k ohm (5 phr CMS). CMS's XPS spectrum revealed a high carbon-to-oxygen atomic ratio (74.47 and 25.53 %). The carbon and oxygen -containing functional groups of CMS acted as a catalyst to improve interfacial interaction of the composites thereby leading to higher mechanical properties. These improved properties were explored in the real-time device and output voltage generation with high durability was tested. From measurements, it was found that the output voltage from the piezo-electric energy harvesting device was around 1.25 V and high durability of 0.5 million cycles was reported.