Food-Based Highly Sensitive Capacitive Humidity Sensors by Inkjet Printing for Human Body Monitoring

Electronic sensors for human body health and activity monitoring applications still face challenges, such as nonbiodegradability and high production costs. As a kind of electronic device with noncontact characteristics, humidity sensors are playing an increasingly important role in monitoring human health. In this work, the humidity sensors were prepared by depositing edible sodium carboxymethyl cellulose (CMC) ink on a biodegradable substrate polylactic acid (PLA) via an inkjet printing technology, which not only effectively reduces the risk of pollution to the human body but also greatly reduces the production costs. The humidity sensor based on CMC has ultrahigh sensitivity (56424%), short response time (0.5 s), good cyclic stability, and exhibits excellent performances in real-time monitoring applications for human breathing and noncontact fingertip movement. Therefore, our research will contribute to the large-scale preparation of high-performance, environmental friendly, and low-cost humidity sensors, and the development of monitoring technology in human health.