Low-Cost Diaper Wetness Detection Using Hydrogel-Based RFID Tags

There is an opportunity to utilize wearable, consumer-oriented sensors for self-health monitoring and preventative medicine. Disposable diaper with built-in lowcost, disposable moisture sensors is one such product. Diaper users include infants, elderly, disabled individuals, and hospital patients. Event-based alerting can enhance care of this population by improving incontinencemanagement, preventing rashes and infections, and avoiding embarrassment. Collected data can be used to optimize change intervals, thereby reducingwaste and expense. In this article,we realize a novel disposable sensor for moisture detection leveraging the material properties of the water absorbing polymer gel common to most diapers. We demonstrate a functional UHF RFID moisture monitor based on hydrogel sensing and propose a hybrid sensor design utilizing metal and hydrogel optimized for a specific diaper geometry. The proposed sensor design achieves a 1-meter read range, a bend radius of <; 20mm, is insensitive to sensor orientation relative to the reader, and is lower-cost than sensors with metallic antennas. We detail design considerations for integration with manufacturing processes and conclude by exploring possible future applications enabled by hydrogel sensing.