Hybrid integration of flexible temperature and humidity sensors with crosstalk decoupling for wearable physiological monitoring

Accurate, synchronous monitoring of respiratory and cutaneous temperature and humidity is essential for assessing pulmonary function and exercise-induced metabolic status. However, miniaturized flexible sensors often suffer from temperature-humidity crosstalk, which degrades measurement reliability. Here, we present a flexible temperature-humidity sensor that achieves crosstalk decoupling through hybrid integration of thermoelectric temperature sensing and capacitive humidity sensing, combined with algorithmic compensation. A 3D interconnected copper-constantan thin-film thermocouple is fabricated on a polyimide substrate for temperature measurement. On the same substrate, a capacitive humidity sensor is constructed using laser-induced graphene interdigital electrodes and a graphene oxide sensing layer. Leveraging the intrinsic immunity between ionic and electronic conduction mechanisms, together with compensation algorithms, real-time decoupled sensing is achieved. The device exhibits an average humidity sensitivity of 31 pF/%RH (relative humidity) and a temperature sensitivity of 29.88 µV/°C, with fast response and recovery. A flexible printed circuit-based acquisition module with wireless transmission is further developed for wearable operation. Demonstrations in respiration monitoring and exercise metabolic assessment scenarios confirm the reliable capture of temperature-humidity dynamics, highlighting the potential of the proposed sensor for wearable healthcare applications.