Highly sensitive and wrappable room temperature wireless gasochromic and chemiresistive dual-response H2 sensors using spray coating

Developing highly reliable, sensitive and room temperature operation hydrogen (H2) sensors is essential to adapt successfully to the H2 economy. Despite the development of various H2 sensors, detecting leaks and pinpointing their precise location remains challenging because of the highly diffusive nature of H2 and environmental factors such as the wind direction. This study reports the development of room temperature, wireless, dual-signal, wrappable, chemiresistive, and eye-readable gasochromic H2 sensors using solution-based and low temperature annealed SnO2/WO3 films on polyimide substrate. These sensors can be wrapped around any point source, such as flanges, rendering the early detection and pinpointing of H2 leaks. An optimized spray-coated gasochromic WO3 film achieves a color change value (ΔE) of 11 with a 6 s response time at 4% H2 and low eye detectable limit of 0.2%. Simultaneously, because a patterned spray-coated gasochromic layer does not interfere with the active area of a SnO2-based chemiresistive sensor, the resistance value of the sensor changes by more than 11,000 times at 1% H2 with a wide concentration range from 0.005% to 2% of H2 at room temperature. Such a sensor can be easily applied to various nonplanar surfaces, while the Bluetooth system integration enables wireless monitoring via smartphones. Our study provides a simple strategy to develop wrappable dual-signal wireless sensors for reliable detection and monitoring of H2 leaks at room temperature.