A Review on Graphene Fibers: Expectations, Advances, and Prospects.

Graphene fiber (GF) is a macroscopically assembled fibrous material made of individual units of graphene and its derivatives. Beyond traditional carbon fibers, graphene building blocks consisting of regulable sizes and regular orientations of GF are expected to generate extreme mechanical and transport properties, as well as multiple functions in smart electronic fibrous devices and textiles. Here, the features of GF are presented along four lines: preparation, morphology, structure-performance correlations, and state-of-the-art applications as flexible and wearable electronics. The principles, experiments, and keys of fabricating GF from graphite with different methods, focusing on the industrially viable mainstream strategy, wet spinning, are introduced. Then, the fundamental relationship between the mechanical and transport properties and the structure, including both highly condensed structures for high-performance and hierarchical structures for multiple functions, is presented. The advances of GF based on structure-performance formulas boost its functional applications, especially in electronic devices. Finally, the possible promotion methods and structural-functional integrated applications of GF are discussed.