A flexible sensor based on a multilayer polymer/AgNW composite film for temperature and strain sensing

Flexible sensors with high sensitivity and mechanical robustness are essential for emerging applications in wearable electronics and health monitoring. This study presents a multifunctional flexible sensor based on a PVA/PDMS/PVA/AgNW composite film fabricated via an in situ method. By incorporating polyvinyl alcohol (PVA) layers on both sides of a polydimethylsiloxane (PDMS) substrate, the multilayer structure effectively addresses the mechanical limitations of single-layer polymer films, which are prone to surface fractures under minimal stress. The composite films exhibit tunable sensing performance. Films prepared with a 7 wt% PVA solution exhibit reproducible responses over repeated heating-cooling cycles, with a rapid response time of 0.87 s upon heating. In contrast, films fabricated with a 3 wt% PVA solution show enhanced sensitivity to mechanical deformation, attributed to stress-induced wrinkling that improves stretchability and reversible deformability under repeated bending cycles. The in situ fabrication method enables lower resistance and better patterning compared to conventional ex situ approaches. Furthermore, the films exhibit excellent conformability to irregular surfaces, biocompatibility, and stable dynamic performance, as demonstrated by real-time finger-bending tests. This work provides a versatile platform for designing flexible sensors capable of detecting both temperature and strain, with potential applications in wearable physiological monitoring, smart electronics, and multifunctional sensing systems.