A Review of Evaluation, Principles, and Technology of Wearable Electromagnetic Harvesters

With the rapid advancement of artificial intelligence, the Internet of Things (IOT), and metaspace technology, smart wearables have become increasingly prevalent. These devices incorporate a variety of sensors, actuators, and signal transmission devices, making the energy supply a critical factor. It is essential to consider energy sources within the human body or in the surrounding environment. Mechanical energy harvesters play a crucial role in the energy supply of smart wearable devices based on piezoelectric, triboelectric, and electromagnetic effects. By exploring different modes of mechanical-to-electrical energy conversion, electromagnetic generators (EMGs) were focused on in this study due to their high conversion efficiency along with the ability to generate high current at low voltage and resistive impedance. The study covered the physical principles, evaluation, and current designs of electromagnetic generators (EMGs) used to convert human body motion into electric energy. However, it is worth noting that despite the advantages of EMGs, their heavy weight, large size, and complexity have limited their application in wearable electronic devices. This highlights the need for a future vision of smart wearable energy harvesters: a miniaturized, high-output, and flexible EMG. Such advancements would address the current limitations and contribute to the development of more efficient and practical wearable electronic devices. The concept of a miniaturized, high-output, and flexible EMG aligns with the demands of current development and emerging technologies like nanogenerators.