Cellulose fiber-based, yarn-based, and textile-based hydroelectric nanogenerators: a mini-review

Research into hydroelectric nanogenerators that use cellulose-based fibers, yarns, and textiles as core substrates has increased in response to the development of wearable electronic devices and the growing urgency to address environmental problems. Hydroelectric nanogenerators produce electric power by streaming water through active materials on the surfaces of core substrates. Water is an abundant resource that can be found in many forms on Earth, including sweat, moisture in the air, hot springs, and seawater. Therefore, hydroelectric nanogenerators have the power potential to generate electricity without location being a significant limitation. Since water capillary action is a key mechanism for power generation, the efficiency of hydroelectric nanogenerators primarily depends on the properties of active materials and core substrates. Cellulose-based fibers, yarns, or textiles are appealing materials for hydroelectric nanogenerator substrates because of their excellent water absorption and wetting properties. Furthermore, cellulose-based fibers are suitable substrates for wearable devices owing to their comfort, breathability, and softness. Therefore, hydroelectric nanogenerators have been mostly fabricated using cellulose-based fibers, yarns, or textiles in recent studies. This mini-review summarizes the technological advances and evolution of hydroelectric nanogenerator systems using cellulose-based substrates. It also discusses the fabrication methods and mechanisms of nanogenerators using different active materials, providing insights into the advantages and disadvantages of each material system. Opportunities for enhancing the electrochemical properties of cellulose-based hydroelectric nanogenerators are discussed, and this will guide future research.