Highly sensitive flexible high-temperature sensor based on ITO/In2O3 for underwater hot spring monitoring
Underwater hot spring monitoring demands sensors that withstand temperatures exceeding 200 °C, rapid thermal fluctuations, and corrosive seawater while maintaining flexibility for deployment on irregular rock surfaces. This study presents a flexible high-temperature sensor utilizing conductive indium tin oxide (ITO) and sensitive In2O3 as sensing layers, deposited on polyimide and encapsulated with PET. Simulation and experimental results demonstrate a sensitivity of 179.6 μV/°C during rapid cooling from various temperatures to 25 °C without applied pressure, with a maximum output variation of 5.76% under 20 MPa. The serpentine electrode structure reduces internal stress, enabling stable output after 10,000 bending cycles. The sensor operates stably from 30 to 300 °C in air, water, seawater, and silicone oil, achieving an output voltage of 41.91 mV and sensitivity of 175.21 μV/°C near 300 °C in silicone oil. In seawater, continuous operation for 20 h and immersion for 48 h resulted in an average output variation of only 1.94%, confirming corrosion resistance and long-term stability. These metrics address the limitations of rigid thermocouples and low-temperature flexible sensors, offering a viable solution for in situ temperature monitoring in extreme underwater thermal environments.