A Moss‐Inspired Electroless Gold‐Coating Strategy Toward Stretchable Fiber Conductors by Dry Spinning

Abstract

fiber conductors are appealing because they offer the unique advantage of unnoticeable size in wearing, scalable production, and potential to be woven into the everyday fabrics. Stretchable fiber conductors usually consist of elastic fiber substrates and conductive fillers, and mixing and coating methods are two main approaches to combine elastic substrates and conductive fillers. [8][9][10][11][12][13][14][15][16][17] However, the mixing method requires high volume ratio of conductive filler in the elastic substrate, which usually reduces elasticity; [10,12] whereas, the coating method often raises concerns of delamination due to Young's modulus mismatch between elastomeric polymers and active materials. [18] Furthermore, most fiber conductors reported to date experience a large decrease of conductivity under large strain because of poor control over elastomer/active materials interface.Melt spinning and solution spinning are two scalable approaches previously reported to produce stretchable fiber conductors. The former approach can lead to highly elastic polymer fiber rapidly, but it requires high temperature to melt the raw materials, hence, limits to the scope of available suitable materials. [8,19] Solution spinning, such as wet spinning and electrospinning, involves much milder conditions to be compatible with high-performance conductive nanofillers. Nevertheless, it requires an excessive solution to solidify fibers (e.g., wet spinning), highvoltage conditions (e.g., electrospinning). Typically, it offers poor control over properties of individual fibers.Herein, we report on a novel dry spinning process to fabricate stretchable fiber conductors based on ultrathin gold nanowires (AuNWs). Ultrathin AuNWs were soft, flexible, and analogous to polymeric chains due to small diameter (2 nm), high aspect ratio (>10 000) and good dispersibility, which has been used in various soft sensing and energy devices. [7,[20][21][22][23] The AuNWs could be well mixed with elastic styrene-ethylenebutylene-styrene (SEBS) block copolymer in tetrahydrofuran (THF) to form a viscous and volatile spinning solution to form AuNWs/SEBS fibers in the air. Inspired by mosses, tiny plants that can attach on tree trunk firmly by penetrating their rhizoid in the tree bark, a nanowire-rooted gold/polymer interfacial design by using AuNWs both as "roots" to attach onto Stretchable fiber conductors are appealing in the field of soft electronics due to their potential to be woven into fabrics leading to smart textile electronics. Coating highly conductive metal films onto elastic polymer fibers can be a potential strategy, however, it is nontrivial to achieve strong metal/polymer adhesion to avoid interfacial failure under large mechanical strains. Here, a novel moss-inspired gold-coating strategy by using an ultrathin gold nanowires (AuNWs)-seeded electroless deposition strategy to fabricate stretchable fiber conductors in a dry spinning process is reported. By optimizing Hildebrand's and Hansen's solubility parameter, the AuNWs are dispersed...

Recent Advances in 1D Stretchable Electrodes and Devices for Textile and Wearable Electronics: Materials, Fabrications, and Applications

“…n) Cross‐sectional SEM image and the corresponding EDX mapping image of the AuNWs/SEBS fiber after the growth of the gold film. (m,n) Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…In addition, nanowelding between the CuNWs in the network decreased the contact resistance and granted the yarn a low electrical resistance of 2.5 Ω cm −1 to the yarns (Figure l). Moreover, taking inspiration from moss, Zhao et al used AuNWs as seeds in an elastic yarns to grow Au films by electroless deposition . The yarns showed electrical conductivities of up to 461 S cm −1 .…”

“…g) The conductivity–strain curves on the effect of prestrain levels of the stretchable conductive fibers. (e–g) Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…A dry spinning method, typically used for the large‐scale industrial production of filament yarns, has also been investigated to develop stretchable conductive yarns . In the dry spinning method, polymeric filaments are extracted by extruding the source polymer solutions in a volatile solvent into a warm air environment through the nozzles.…”

“…Further, this process is faster than the wet spinning method. Zhao et al developed stretchable conductive yarns with high conductivity and stretchability by using a dry spinning method and an ultrathin AuNWs‐seeded electroless deposition strategy (Figure e,f) . The AuNWs were well mixed with an highly elastic SEBS block copolymer to form AuNWs/SEBS stretchable yarns through the dry spinning method.…”