Advances in Nanostructured Functional Hydrogels for Energy Harvesting

Nanostructured functional hydrogels have recently emerged as highly versatile and promising materials for sustainable energy harvesting because of their tunable chemical composition, inherent mechanical flexibility, and outstanding ionic conductivity. Their unique three-dimensional polymer networks provide abundant space for the integration of nanostructures, which can significantly improve charge transport pathways, mechanical stability, and responsiveness to a wide range of external stimuli such as pressure, temperature, or humidity. By tailoring molecular design and incorporating functional nanomaterials, these hydrogels can be engineered to achieve superior electrochemical and mechanical performance. This review highlights recent progress in the rational design, fabrication strategies, and advanced applications of nanostructured functional hydrogels in energy harvesting technologies, with particular focus on triboelectric nanogenerators (TENGs), piezoelectric devices, and bioenergy systems. Finally, current challenges, emerging trends, and opportunities for developing next-generation hydrogel-based energy harvesters are critically discussed.