Durable copper nanowires for flexible curvature sensors

• Tuning reaction-temperature intrinsically stabilizes copper nanowires without post-synthetic treatments. • Nanowires retain high electrical conductivity for over 60 days without protective coatings. • Temperature-engineered nanowires enable mechanically robust flexible curvature sensors with stable performance over 10,000 bending cycles. Metal nanowire-based flexible conducting surfaces (FCS) are vital for next-generation flexible and wearable sensors. Copper nanowires (CuNWs) offer a low-cost alternative to the expensive silver nanowires for fabricating FCS, yet their poor stability remains a significant challenge. In this study, we report the synthesis of ultralong CuNWs using a hydrothermal polyol method across a range of temperatures (120 - 180°C). The CuNWs synthesised at 160°C (CuNW-160) demonstrated the best performance. CuNW-160 films maintained stable conductivity for over 60 days in ambient conditions and thermal stability up to 140°C. A capacitive curvature sensor was fabricated using FCS made with CuNW-160, which maintained consistent performance over 10,000 bending cycles and still showed good curvature sensitivity after 75 days. This highlights the potential use of the copper nanowires by tuning reaction temperature for use in reliable, low-cost flexible electronics.