Highly sensitive flexible high-temperature sensor based on ITO/In2O3 for underwater hot spring monitoring

• • Sensitivity of 179.6 μV/°C during rapid cooling to 25 °C without applied pressure, and 175.21 μV/°C near 300 °C in silicone oil, enabling precise tracking of rapid thermal fluctuations in hot spring jets where conventional thin-film thermocouples (type T/K) exhibit sensitivities below 50 μV/°C. • • Maximum output variation of 5.76% under 20 MPa during cooling, demonstrating mechanical robustness essential for deployment in high-pressure deep-sea environments where sensor failure due to pressure-induced signal drift is a critical bottleneck. • • Stable operation after 10,000 mechanical bending cycles due to serpentine electrode design that reduces internal stress, addressing the structural fatigue that plagues rigid sensors on irregular rock surfaces and enabling conformal mounting. • • Average thermoelectric output variation of only 1.94% after 20 h continuous operation and 48 h immersion in seawater, confirming corrosion resistance and long-term stability required for extended monitoring campaigns in saline hydrothermal systems.