A Rigid-Flexible Conformable WSN With Near-Zero Standby Power Based on RF Energy Wake-Up

Wireless sensor nodes (WSNs) operating with low-duty-cycle consume considerable energy during hibernation state due to high standby power, significantly limiting their lifespan. This study highly integrated a flexible antenna, a matching network, a rectifier, and an embedded wireless sensor to constitute a conformable WSN with a compact size of 65× 54 mm. The proposed WSN realizes periodical wake-up by radio frequency (RF) energy transmission that reduces the standby current to 12 nA. A flexible asymmetric dipole antenna is designed to harvest RF energy and make the WSN conformable to curved surfaces with radii exceeding 50 mm. The experimental results indicate the WSN has a maximum wake-up distance of 17.38 m from an RF energy source and a lifespan of 2.7 years under bihourly data acquisition cycles when powered by a 3.7 V, 50 mAh battery. The proposed WSN reduces reliance on the hazardous, inefficient manual maintenance by eliminating battery replacement, significantly enhancing practicality in the application of the Internet of Things (IoT).