Development and characterization of graphene-based sensors and evaluation of multi sensing suitability for wearable applications

This thesis presents a comprehensive study on graphene-based sensors for multi-sensing wearable healthcare applications. Indeed, graphene-based nanocomposites consisting on a polyvinylidene fluoride (PVDF) matrix loaded with graphene nanoplatelets (GNPs) have been employed for the realization of advanced wearable sensors, focusing on cost-effectiveness, multi-functionality, and adaptability across a range of fields, from biomedical monitoring to wearable technology. The research begins with the synthesis of cost-effective graphene based nanofillers, a critical step aimed at making the composite material affordable without compromising its functionality. Through controlled synthesis methods, GNPs with properties suitable for integration into the PVDF matrix have been produced, optimizing the composite final properties and chemical stability. Detailed characterization of the PVDF/GNP composite was conducted to assess its electrical, thermal, and mechanical properties, establishing a foundation for its multi-sensing capabilities. A major contribution of this thesis is the design and fabrication of a multi-modal electrode that simultaneously captures electrocardiogram (ECG) and respiration signals, a novel approach to non-invasive physiological monitoring. This electrode leverages the PVDF/GNP composite's high sensitivity and adaptability, providing a seamless solution for real-time acquisition of multiple biosignals, which holds promise for future applications in wearable healthcare devices. In addition to biomedical applications, we investigated the thermoelectric properties of the PVDF/GNP composite, aiming to develop a robust and efficient thermal sensor. The thermal conductivity of the composite was optimized through careful control of GNP loading, enabling the sensor to detect and respond to temperature changes with high accuracy. This thermoelectric sensor is designed to be low-cost and scalable, making it suitable for applications in environmental monitoring and temperature-sensitive systems. Further, the PVDF/GNP composite was utilized in the development of a force sensor capable of detecting pressure and force changes with high sensitivity. To demonstrate the practical application of this force sensor, we developed a smart insole prototype that integrates the PVDF/GNP force sensor for real-time monitoring of pressure distribution across the foot. This smart insole has significant potential in gait analysis, rehabilitation, and sports science, as it can provide valuable insights into foot pressure dynamics and assist in the development of personalized treatment and training programs. Overall, this thesis demonstrates the PVDF/GNP composite's versatility, highlighting its adaptability for diverse sensor applications and its potential to drive advancements in low-cost, high-performance sensor technologies. The findings contribute to the growing field of flexible electronics and sensor materials, with implications for biomedical devices, environmental sensors, and wearable technologies. By combining in-depth material characterization with innovative sensor design, this research paves the way for future developments in multifunctional, affordable sensor systems that address a broad range of societal and industrial needs.