Island-shaped micro-cracks evolution in ultrathin film enables ultra-sensitive for strain sensors under high temperatures

The advancement of high temperature resistant thin film strain sensors is crucial for detecting surface strain changes in aerospace turbine engines and launch vehicles. However, the strain sensitivity under high temperature thin film strain gauges is generally low, resulting in minimal resistance change under unit strain. In this regard, we proposed a thin film (thickness:∼500 nm) strain sensor, consisting of a composite structure including indium tin oxide with unconventional ratio (5–5 ITO, In₂O₃:SnO₂ = 50:50 wt%) and Pt. Surprisingly, the strain sensor demonstrates ultrahigh sensitivity (gauge factor (GF) > 120, maximal GF = 178), rapid response time (0.12 s), as well as long cycling durability (10 h) under an operating temperature of 500 °C. The outstanding dynamic strain response and long-term temperature cycling stability of sensor originate from the micro-cracks in the sensitive film. The 5–5 ITO thin film produces island-like gaps with stress concentration in high-temperature environments, leading to a significant increase in resistance. Meanwhile, the top layer Pt structure covers the 5–5 ITO film, which aids in better recovery of micro-cracks, enhancing sensor repeatability and cycle durability. With its rapid response time, high sensitivity, and consistent performance at high temperatures, our strategy for this sensor holds great promise for applications in monitoring under extreme environment conditions.