Rigid-flexible thin-film thermocouple temperature sensing and applications

<p indent="0mm">Applications in key hot-end components of aero-engines, advanced manufacturing processes, high-power electronic devices, and wearable systems have created an urgent need for temperature measurement with high spatiotemporal resolution, strong environmental adaptability, and <italic>in-situ</italic> integration capabilities. Thin-film thermocouples (TFTCs), with their advantages of thinness, small heat capacity, fast response speed, arrayability, and <italic>in-situ</italic> fabrication, have become an important technological means for temperature sensing under extreme and complex operating conditions. This review systematically reviews the research progress on the temperature measurement principles, material systems, structural design, and typical applications of rigid and flexible TFTCs from a “rigid-flexible” perspective. For rigid TFTCs, the review focuses on their current application status in high-temperature scenarios such as hot-end components of aero-engines, battery systems, and machining temperature measurement. It summarizes the research progress in improving the upper limit of temperature measurement and service reliability through the development of new thermoelectric materials, the design of protective and transition layers, and thermal stress optimization. For flexible TFTCs, the review systematically focuses on their advantages in wearable health monitoring, electronic skin, and temperature measurement of complex curved surfaces. This review focuses on analyzing the impact of flexible substrates, structural design, and packaging methods on the stability and durability of TFTCs, and summarizes the latest progress in novel flexible high-temperature resistant substrates and additive manufacturing processes. Building upon this foundation, the paper further outlines the key challenges faced by TFTCs in high-temperature stability, interface reliability, multi-field coupling operation, and system-level integration, and provides an outlook on their future development in novel thermoelectric materials, rigid-flexible composite structures, multi-parameter integration, and intelligent sensing systems. This paper can provide a reference for the design optimization and engineering application of TFTC temperature sensors.