Urine-Powered Batteryless Sensor Node With Printed Harvesters and Sensors for Smart Diapers

As the global population ages, caregivers encounter significant challenges in monitoring wet diapers and assessing the volumes of voided fluids in adult incontinence products. Recent advancements in smart-diaper technology address these issues, but challenges persist with integrating electronics, frequent removal and reapplication, and managing batteries. This study presents a batteryless urine-powered IoT sensor node using printed energy harvesters (EH) and capacitive sensors integrated with an ultralow-power integrated circuit for disposable smart diapers. Coplanar capacitive sensors and electrochemical EH are printed on the flexible substrate using environment-friendly materials. An ultralow power frontend interface is developed, which is powered by the harvested energy from urine. Laboratory measurements validate the functionality of on-chip electronics and the performance of in-diaper sensors and EH. The system demonstrates effective energy harvesting by maintaining a stable regulated voltage of 1.1 V with urine volumes of 90 ml or more, powering the front-end electronics continuously for 6 h. The proposed system successfully demonstrated the detection of multiple urination events in the diaper and quantified the voided volume as low as 30 ml. The results demonstrated in this work pave the way for cost-effective, disposable, and environmentally friendly solutions for smart diapers, enhancing both efficiency and comfort for caregivers and elderly individuals.