High-sensitivity and durable MWCNT@CuNp/silicone rubber flexible strain sensor for human motion detection and composite structural monitoring

Flexible strain sensors have attracted wide attention in various applications, such as wearable electronic devices, human motion detection, and soft robotics, due to their ability to measure mechanical deformation with a high degree of adaptability. In this study, we developed a silicon-based flexible strain sensor with a three-layer sandwich structure consisting of a silicon rubber substrate and MWCNT@CuNPs conductive material. The mixing of multi-walled carbon nanotubes (MWCNTs) and copper nanoparticles (CuNPs) aims to improve the electrical conductivity, sensitivity, and mechanical stability of the sensor. The sensor using MWCNT@CuNp material shows a sensitivity improvement of about 200 compared to the SR@MWCNT@AgNp sensor, indicating superior electromechanical performance. The MWCNT@CuNp sensor test results show that the sensor has a measuring factor (GF) of 8.09 with high linearity (R² = 0.99) in the 0�80 strain range. Mechanical durability tests showed that the sensor was able to withstand up to 1,200 loading and unloading cycles without significant performance degradation, proving its reliability for applications with repetitive strain. In addition, this sensor shows potential to be applied to various systems that require high sensitivity, good linearity, and superior mechanical durability. This sensor can not only be used in electronic skin to detect finger, wrist, elbow, and knee movements but also plays a role in monitoring strain changes in PLA/fiber glass/PLA composite materials during bending tests. These capabilities open opportunities for MWCNT@CuNPs sensors to be integrated in various engineering applications and smart material technologies. © 2025 Elsevier B.V.