Development of conducting polymer-based composites for flexible gas sensor devices

Abstract

In the realm of gas sensing technologies, there has been a remarkable upswing in demand for sensors that are not only flexible and wearable but also versatile, able to monitor a variety of environmental markers from pollutant levels to human respiratory rates. This dissertation delves into the exploration and advancement of these wearable, flexible gas sensors made from conducting polymers (CPs), emphasizing their potential when integrated with Carbon Nanotubes (CNTs) and two-dimensional (2D) materials, such as graphene and MXenes. For the first time, disposable masks, predominantly comprised of polypropylene (PP) fibers, were leveraged as flexible substrates for wearable sensing applications. When combined with conducting polymers and bolstered by CNTs or 2D materials, these disposable or discarded masks facilitate a straightforward synthesis process, leading to cost-effective and high-sensing performance (e.g., excellent sensitivity and selectivity, rapid response/recovery time towards target gas) nanocomposites. The pivotal discoveries of this dissertation include: Breath Analysis and Odor Detection: Our innovatively crafted wearable wireless Bluetooth sensors displayed exceptional promise in breath analysis, particularly in charting human respiratory rates. Furthermore, these sensors proved adept in identifying foul-smelling gases for potential health monitoring and detecting food degradation. Effects of External Factors: Through meticulous experimentation, we discerned the sensors' reactions under diverse conditions, such as varying synthesis sequences, gas concentrations, temperature shifts, humidity levels, component ratios, and even in different physical states like bending or folding. While these sensors might retain their sensitivity, subtle variations were noticed. These can be ascribed to the intrinsic qualities of the conducting polymers and their interplay with the embedded nanostructures. Sensing Mechanism Exploration: A thorough exploration into the sensing mechanism highlighted the collaborative roles, such as the formation of heterojunctions, enhanced conductivity, and increased specific surface areas, of the conducting polymer when integrated into a hybrid structure with other materials. This synergy not only boosted the sensor's capability but also provided insights into the dynamics of charge carrier transfers and their pivotal role in gas detection. The notable improvements in the performance of the fabricated flexible gas sensors underline the immense potential in melding conducting polymers with cutting-edge nanomaterials. Harnessing waste masks for such sophisticated purposes accentuates the potential for eco-friendly advancements in wearable technology. The potential applications of these enhanced sensors span medical diagnostics, environmental surveillance, and industrial safety measures. By leveraging the unique properties of conducting polymers and amalgamating them with nanostructures, we have developed advanced, flexible, wearable gas sensing devices, setting the stage for a future where these sensors are an integral part of our daily lives.