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.