Facile Fabrication of Highly Flexible and Sensitive Strain Sensors Based on UV-laser-reduced Graphene Oxide with CuO Nanoparticles for Human Health Monitoring

Applications of graphene-based materials in wearable devices have garnered significant attention owing to their excellent mechanical and electrical properties. However, graphene fabrication is hindered by its inherent structural characteristics, which necessitates the development of alternative materials for strain sensors. In this study, a novel flexible resistive-type strain sensor composed of a unique three-dimensional conductive carbon network was fabricated using a UV pulsed laser. Using a 355-nm UV pulsed laser, composites based on UV laser-reduced graphene oxide (UV-LRGO) with CuO nanoparticles on a PDMS substrate (Cu/UV-LRGO/PDMS) were selectively fabricated via direct laser writing. This fabrication method offers a contact-free, environmentally sustainable, and cost-effective approach, providing a streamlined one-step process that eliminates the necessity for toxic chemicals, thermal reduction, and complex protocols. The composites were meticulously characterized via various spectroscopic techniques. Notably, the proposed sensor exhibited robust performance, withstanding 7,200 stretching-relaxing cycles and accommodating strains of up to 25%, while also exhibiting a high strain gauge factor (~ 1026 GF). This work introduces a straightforward strategy for fabricating flexible strain sensors with high sensitivity and remarkable repeatability for human health monitoring, and observations including wrist pulses, finger banding, and facial eyebrow movements can be effectively monitored.