Scalable rGO–Ni Hybrid Yarn Sensors for Durable and Sensitive Wearable Electronics

Wearable electronics, particularly strain sensors, are essential for applications in health monitoring and human-machine interfaces. However, challenges remain in achieving sensors that balance high sensitivity, mechanical flexibility, and durability under dynamic deformations and environmental stressors like washing and humidity. Existing materials often suffer from limitations in conductivity, mechanical flexibility, and long-term stability. This study introduces a novel hybrid composite sensor composed of reduced graphene oxide (rGO) and nickel (Ni) coatings on spandex-cotton (CoSP) yarn, encapsulated in polydimethylsiloxane (PDMS). The synergistic combination of rGO and Ni significantly enhances the sensor’s mechanical strength, electrical conductivity, and strain sensitivity. The PDMS coating further ensures long-term durability, protecting the conductive network from oxidation and degradation. The rGO–Ni–CoSP/PDMS composite exhibits a tensile strength of 534 MPa and an elongation at break of 595%. The sensor shows excellent piezoresistive behavior with a gauge factor of -6.11 at 100% strain and maintains over 90% of its initial conductivity after 50 wash cycles. Additionally, the sensor demonstrates stable, repeatable resistance changes after 15,000 stretching cycles, with negligible hysteresis, confirming its high reliability and durability. This research presents a significant advancement in wearable strain sensors, offering a robust, sensitive, and environmentally stable solution. The sensor’s ability to monitor physiological activities such as respiration, pulse, and muscle movements highlights its potential for applications in healthcare, wearable robotics, and personalized health monitoring. Additionally, a mathematical model was established and experimentally validated, providing predictive insight into the strain-dependent resistance behavior of the hybrid yarn sensor.