A Fully Printed Cobalt-Based Metal-Organic Framework Humidity Sensor for Wearable Sweat-Rate Monitoring in Industrial Settings

In the context of Industry 5.0, the possibility of reliably monitoring the physiological well-being of industrial workers represents a growing priority. Focusing on the exploitation of non-invasive wearable devices, this study introduces a fully printed, flexible humidity sensor designed for continuous sweat-rate monitoring. The solution was specifically designed to work in low-perspiration conditions, which are common during near-rest or at-rest states. The device integrates inkjet-printed silver interdigitated electrodes coated with a Cobalt-based metal-organic framework active layer, which provides high sensitivity through efficient water-binding kinetics. Laboratory characterization confirmed a linear response between 50% and 95% relative humidity (RH), with an average sensitivity of 0.06 Log(Ω)/% RH. In vivo validation demonstrated that the proposed solution effectively captures the skin-sensor microclimate humidity (ranging from 80% to 95% RH) and closely correlates with the tonic phase of Electrodermal Activity signals. These findings supported the validation of the proposed platform as a reliable, pump-free microfluidic solution for tracking the subtle transition from basal perspiration to active sweat production.