Wearable Image‐Based Colorimetric Sensor for Real‐Time Gas Detection with High Chromaticity

Abstract Flexible gas sensing technologies are essential for a wide range of environments and applications, from wearable devices to large‐scale industrial systems. Among various approaches, colorimetric sensing stands out for its distinct advantages, including energy‐free operation, intuitive visual feedback, and high resistance to environmental disturbances. Leveraging ultrathin resonators, colorimetric sensing achieves enhanced chromaticity and angular stability. In this study, a flexible colorimetric gas sensor is introduced based on a resonator array integrated with polyvinyl alcohol (PVA). This sensor achieves nearly 100% coverage of the standard RGB color gamut, enabling precise and visually distinguishable gas detection. Fabricated on a flexible substrate, it demonstrates remarkable angular robustness, maintaining consistent color under incident light angle variations of up to 60°. This capability, combined with rapid response times of 180 ms for PVA swelling and 210 ms for shrinking, highlights the sensor's adaptability for diverse applications, including wearable devices and industrial‐scale monitoring. Furthermore, the sensor is evaluated under various volatile organic compounds (VOCs) and imaging conditions, showcasing its potential for image‐based analysis and accurate VOC detection. Notably, it demonstrated the ability to detect VOC concentrations that are indistinguishable using a single sensor by simultaneously analyzing data from four sensor arrays.