A Review of Hydrogel Fiber: Design, Synthesis, Applications, and Futures

Hydrogel fibers (HFs) are abundant in living organisms, including the three major tissues of the human body, that is, muscle, nerve, and connective tissue, which have the ability to transport materials and deliver energy, playing a crucial role in carrying out essential life functions through a collaborative bottom-up construction of function and structure. Therefore, the development of functional HFs that closely mimic biofunction ability is highly desirable. HFs are characterized by their high water content and have a fibrous shape with a cross-linking network in condensed structures. They combine the functional characteristics of hydrogel materials (soft, wet, environmentally, responsive, biocompatible) with the structural advantages of fiber materials (high aspect ratio, anisotropy, flexibility). Therefore, a systematic understanding of the development and current challenges of HFs is of great significance for their functionalization and structural construction, potentially leading to the realization of bionic functions similar to those found in the human body. This paper discussing the development of HFs, focusing on material composition, structural design, functional construction, and applications, while also addressing the limitations and challenges associated with HFs in detail. The goal of this review is to provide guidelines for the construction of functional or bionic HFs and their practical applications.