Development of a CNT/Bi2S3/PVDF composite waterproof film-based strain sensor for motion monitoringl

An innovative flexible electronic device was developed by integrating functionalized carbon nanotubes, bismuth sulfide nanostructures, and a polyvinylidene fluoride matrix to create a highly water‐resistant strain detection platform. The fabricated film exhibited a remarkable static water contact angle of 141°, with only a 3–4° reduction after 48 hours of immersion, confirming its excellent hydrophobic performance. Mechanical testing revealed a tensile strength of 43.2 MPa and maintained over 96% of its original strength following 1000 bending cycles, thereby demonstrating outstanding durability under repetitive deformation. Electrical characterization showed an initial conductivity of 12.3 S/m and a baseline resistance near 98 Ω, with less than a 5% change observed during cyclic loading. Furthermore, the device achieved a gauge factor of 76 within the linear strain region up to 60%, indicating high sensitivity to applied stress. Dynamic performance assessments recorded rapid response and recovery times of 0.12 and 0.15 seconds, respectively, enabling real-time monitoring of mechanical variations. In practical demonstrations, the sensor delivered distinct resistance increments of 35% during full finger flexion and 28% during wrist movements. Long-term evaluations conducted over 60 days under fluctuating temperature (15 °C to 35 °C) and humidity conditions (40% to 90% RH) showed a normalized response variation of less than 3%. These quantitative results confirm that the proposed device offers a balanced combination of mechanical robustness, electrical stability, and rapid responsiveness, making it a promising candidate for next-generation wearable electronics and health monitoring applications. These findings lay a robust foundation for further exploration and optimization in advanced flexible devices.