Bio-Inspired Stretchable and Contractible Tough Fiber by the Hybridization of GO/MWNT/Polyurethane

Abstract

Spider silks represent stretchable and contractible fibers with high toughness. Those tough fibers with stretchability and contractibility are attractive as energy absorption materials, and they are needed for wearable applications, artificial muscles, and soft robotics. Although carbon-based materials and poly(vinyl alcohol) (PVA) composite fibers exhibit high toughness, they are still limited in low extensibility and an inability to operate in the wet-state condition. Herein, we report stretchable and contractible fiber with toughness that is inspired by the structure of spider silk. The bioinspired tough fiber provides 495 J/g of gravimetric toughness, which exceeds 165 J/g of spider silk. Besides, the tough fiber was reversibly stretched to-80% strain without damage. This toughness and stretchability are realized by hybridization of aligned graphene oxide/multiwalled carbon nanotubes in a polyurethane matrix as elastic amorphous regions and β-sheet segments of spider silk. Interestingly, the bioinspired tough fiber contracted up to 60% in response to water and humidity similar to supercontraction of the spider silk. It exhibited 610 kJ/ m3 of contractile energy density, which is higher than previously reported moisture driven actuators.

Spider Silk‐Inspired Artificial Fibers

“…Upon water absorption, the stretched polymer chains could be rearranged, resulting in a fiber supercontraction of 59%. [ 107 ]…”

Strategy to Fabricate a Strong and Supertough Bio-Inspired Fiber with Organic–Inorganic Networks in a Green and Scalable Way

“…Compared with their results, we enhanced the strength greatly (more than 4 times) without sacrificing the toughness by a green and scalable method. It should be emphasized, to the best of our knowledge, that our results (between 167 MPa and 640 MJ m –3 and 442 MPa and 362 MJ m –3 ) of hybrid fiber are estimated to be the highest reported to date for PUAFs (Figure d). ,,,− It is worth noting that the hybrid fiber can be produced with the film strip in a large-scale manner, and the film strip can also be connected due to the self-healing effects without reducing its mechanical character (Figure S16). Due to the inner strong interactions and excellent water resistance of our fiber, its mechanical strength can still remain at 170 MPa and the elongation can reach 445% after being immersed in water for 72 h (Figure S17).…”

“…So, tremendous efforts have been made to reproduce its mechanical properties using artificial fibers. For example, the regenerated or functionalized silk fibers, PVA based nanohybrid fibers were studied. ,− But, their applicability is restricted by either low availability or water-solubility and uncontrollable quality for these processes. To overcome the above problems, recently, polyurethanes (PUs) have aroused close attention due to their excellent mechanical properties and easy availability.…”

“…To overcome the above problems, recently, polyurethanes (PUs) have aroused close attention due to their excellent mechanical properties and easy availability. The properties such as stretchability, abrasion resistance, and strength can be tailored by adjusting the chemical constituents and ratio of the soft (polyols) and hard segments (diisocyanate). − The Kim group mixed GO, CNT, and PUs in an organic solvent to prepare a water-insoluble fiber with high strength (114 MPa) and toughness (543.7 MJ m –3 ) by the wet spinning method . Very recently, to improve the strength and toughness of PUs simultaneously, Hu et al tried to synthesize a special hard part in the PUs macromolecule to mimic the β-sheet structure and prepare the PUs artificial fiber (PUAF) with a dry spinning method by evaporating hexafluoroisopropanol (HFIP) solvent under infrared radiation.…”

Bioinspired Design of Graphene‐Based Materials

“…© 2020 Wiley-VCH GmbH regions). [142] Interestingly, like its natural counterpart, such a material displays humidity-driven contraction, a behavior typical of a silk microstructure resulting from the entropy-driven recoiling of molecular chains upon water absorption.…”