Highlighting Recent Progress in Fiber Energy Harvesters: From Working Principles to Future Perspectives

As electronics proliferate through the rise of the internet of things (IoT) and artificial intelligence (AI), the need for sustainable, decentralized power source is growing. Energy harvesting-converting ambient sources such as vibration, heat, or electromagnetic waves into electricity-offers a promising solution for powering distributed, low-power, or wearable electronic systems. However, the practical deployment of most energy harvesters has been significantly limited by the processability issues associated with the inherent brittleness of conventional materials. In contrast, fiber-based energy harvesters offer superior flexibility and stretchability due to their intrinsic deformability and multidirectional bending capabilities, presenting a compelling alternative to conventional energy harvesters. This review systematically summarizes the fabrication processes and performance characteristics of fiber energy harvesters, categorizing them by the origin of the energy source-mechanical, optical, and thermal. In particular, various design considerations based on the working principles of fiber energy harvesters are retrospectively analyzed to provide guidelines for developing next-generation fiber energy harvesters. Additionally, current challenges and future research directions are discussed, highlighting the potential of fiber-based platforms to enable next-generation wearable electronics.