Advances in Humidity-Driven Energy Harvesting: A Review of Mechanisms, Materials, and Scalability Challenges

This review systematically summarizes recent advances in moisture-electric generation technology from four perspectives: functional-material modification, device-structure design, multi-source energy-harvesting strategies, and practical applications. It discusses the classification and modification of moisture-responsive functional materials; analyzes how device architectures regulate ion transport, reviews the mechanisms of coupling moisture energy with solar, thermal, and mechanical energy; and summarizes representative applications of moisture-electric generators (MEGs) in power supply, self-powered sensing, and wearable electronics. The review further compares the advantages and limitations of different material and structural strategies and evaluates challenges related to output performance, environmental adaptability, long-term stability, power management, and scalable fabrication. Finally, future research directions are discussed to support the practical development of MEGs.