A fully-enclosed wrist-wearable hybrid nanogenerator for self-powered sensors

This paper presents a fully-enclosed wrist-wearable hybridized electromagnetic-triboelectric nanogenerator (FE-HNG) for scavenging energy from the low-frequency human wrist motion (≤ 5 Hz). The FE-HNG incorporates the rolling electrostatic induction and electromagnetic induction using a freely moving magnetic ball inside a hollow circular tube. A thin flexible flux concentrating material is introduced to increase the emf and enhances the electromagnetic output performance.

• Development of a fully-enclosed, wrist-wearable hybridized nanogenerator (FE-HNG).
• Effective energy harvesting from diverse and irregular low-frequency wrist motions.
• Introduction of a flexible flux concentrating material to enhance electromagnetic performance.
• Demonstrated ability to power a commercial wristwatch for over 23 minutes from just 5 seconds of motion.

The FE-HNG was fabricated as a fully-enclosed unit containing a freely moving magnetic ball in a circular tube to generate power through both electromagnetic and triboelectric effects. A flexible flux concentrating material was incorporated to boost the electromagnetic output. The device's performance was evaluated by its ability to harvest energy from various irregular wrist motions and its capacity to power a commercial electronic device.

The FE-HNG achieves an average power density of 0.118 mW cm⁻³ and can drive a commercial wrist-watch continuously for more than 23 minutes from just 5 seconds of wrist motion. This successful demonstration renders an effective approach for scavenging wasted biomechanical energy and provides a promising solution towards the development of sustainable power supply for wearable electronic devices and self-powered healthcare monitoring sensors.