Textile-integrated wearable energy devices: advances in hydrogel fibers for aqueous flexible energy storage

Abstract

Hydrogels have emerged as promising materials for aqueous flexible energy storage devices (AFESDs) due to their exceptional properties, including high shape adaptability, intrinsic conductivity, biocompatibility, elasticity, and responsiveness to external stimuli. Among various hydrogel formats, one-dimensional (1D) hydrogel fibers (HFs) have attracted growing interest owing to their superior mechanical flexibility, lightweight nature, and compact form factor, attributed to their highly aligned polymer chains. These advantages render HFs particularly well-suited for AFESDs compared to three-dimensional (3D) bulk gels and two-dimensional (2D) films. Despite their potential, systematic studies on HFs remain limited, with few comprehensive evaluations of their design, performance, and challenges. This review provides a critical overview of recent progress in HF-based materials, encompassing material design, synthesis strategies, fabrication methods, device architectures, and operational mechanisms. Emphasis is placed on their applications as electrodes and electrolytes in flexible capacitors and integrated AFESDs. This review also identifies current limitations and technical bottlenecks of HF-related AFESDs in terms of conductivity enhancement, mechanical performance balancing, interfacial stability, and environmental adaptability, offering insights into future research directions. By consolidating current knowledge, this work aims to support further development and broader recognition of HFs in the field of flexible energy storage.