Wearable Humidity Sensor Using CsCuI Metal Halides with Hydroxyl Selective Phase Transition for Breath Monitoring.

The low-dimensional metal halide CsCuI exhibits unique electrical and chemical properties. Notably, it undergoes a phase transition to CsCuI upon exposure to hydroxyl (-OH) gas, resulting in significant changes in its electrical characteristics. In this study, we developed a highly selective semiconductor-based gas sensor utilizing CsCuI. The material was synthesized on an AlO substrate with carbon electrodes using a solution-based process, enabling gas sensing based on its electrical properties. The sensor was further integrated into an Arduino-based real-time monitoring system for wearable applications. The final system was mounted onto a face mask, enabling the real-time detection of human respiration. This research presents a next-generation sensor platform for real-time respiratory monitoring, demonstrating the potential of CsCuI in advanced wearable bio-gas sensing applications.