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An artificial spinning system using regenerated silk fibroin solutions is adopted to produce high-performance silk fibers. In previous studies, alcohol-based agents, such as methanol or ethanol, were used to coagulate silk dope solutions, producing silk fiber with poor mechanical properties compared with those of native silk fibers. The alcohol-based coagulation agents induce rapid β-sheet crystallization of the silk molecules, which inhibits subsequent alignment of the β-sheet crystals. Here, we induce gradual β-sheet formation to afford adequate β-sheet alignment similar to that of native silk fiber. To this aim, we developed an amorphous silk fiber spinning process that prevents fast β-sheet formation in silk molecules by using tetrahydrofuran (THF) as a coagulation solvent. In addition, we apply postdrawing to the predominantly amorphous silk fibers to induce β-sheet formation and orientation. The resultant silk fibers showed a 2.5-fold higher extensibility, resulting in 1.5-fold tougher silk fibers compared with native Bombyx mori silk fiber. The amorphous silk fiber spinning process developed here will pave the way to the production of silk fibers with desired mechanical properties. [ABSTRACT FROM AUTHOR]

Conspectus Electrospinning is a simple and versatile technique that relies on the electrostatic repulsion between surface charges to continuously draw nanofibers from a viscoelastic fluid. It has been applied to successfully produce nanofibers, with diameters down to tens of nanometers, from a rich variety of materials, including polymers, ceramics, small molecules, and their combinations. In addition to solid nanofibers with a smooth surface, electrospinning has also been adapted to generate nanofibers with a number of secondary structures, including those characterized by a porous, hollow, or core-sheath structure. The surface and/or interior of such nanofibers can be further functionalized with molecular species or nanoparticles during or after an electrospinning process. In addition, electrospun nanofibers can be assembled into ordered arrays or hierarchical structures by manipulation of their alignment, stacking, and/or folding. All of these attributes make electrospun nanofibers well-suited for a broad spectrum of applications, including those related to air filtration, water purification, heterogeneous catalysis, environmental protection, smart textiles, surface coating, energy harvesting/conversion/storage, encapsulation of bioactive species, drug delivery, tissue engineering, and regenerative medicine. Over the past 15 years, our group has extensively explored the use of electrospun nanofibers for a range of applications. Here we mainly focus on two examples: (i) use of ceramic nanofibers as catalytic supports for noble-metal nanoparticles and (ii) exploration of polymeric nanofibers as scaffolding materials for tissue regeneration. Because of their high porosity, high surface area to volume ratio, well-controlled composition, and good thermal stability, nonwoven membranes made of ceramic nanofibers are terrific supports for catalysts based on noble-metal nanoparticles. We have investigated the use of ceramic nanofibers made of various oxides, including SiO2, TiO2, SnO2, CeO2, and ZrO2, as supports for heterogeneous catalysts based on noble metals such as Au, Pt, Pd, and Rh. On the other hand, the diameter, composition, alignment, porosity, and surface properties of polymeric nanofibers can be engineered in a controllable fashion to mimic the hierarchical architecture of an extracellular matrix and help manipulate cell behaviors for tissue engineering and regenerative medicine. To this end, we can mimic the native structure and morphology of the extracellular matrix in tendon using uniaxially aligned nanofibers; we can use radially aligned nanofibers to direct the migration of cells from the periphery to the center in an effort to speed up wound healing; and we can also use uniaxially aligned nanofibers to guide and expedite the extension of neurites for peripheral nerve repair. Furthermore, we can replicate the anatomic structures at the tendon-to-bone insertion using nanofiber scaffolds with graded mineral coatings. In this Account, we aim to demonstrate the unique capabilities of electrospun nanofibers as porous supports for heterogeneous catalysis and as functional scaffolds for tissue regeneration by concentrating on some of the recent results. [ABSTRACT FROM AUTHOR]

Spinning of cellulose nanofibrils (CNF) offers promising opportunities to develop renewable fibers and filaments with strong, aligned structure. This review introduces recent findings on the relationship between the properties of CNF hydrogels, the spinning conditions and the performance of filaments obtained by dry- and wet-spinning. For example, the filament Young's modulus correlates with CNF structural factors, such as slenderness and crystallinity. Furthermore, high shear rates and extensional flow strengthen the filament, mainly by improving structural uniformity and partly by effectively orienting the fibrils. However, other less obvious factors, such as those associated with coagulation and drying, play critical roles in filament performance. These and other details related to this timely application of CNF are presented here for the benefit of researchers and users of fibers and filaments for composites, textiles and others. [ABSTRACT FROM AUTHOR]

Graphene macroscopic materials have attracted tremendous attention for their fascinating performance and rich functionalities. Here, we provide an elaborate description of techniques in the fabrication of graphene macroscopic materials, focusing on the wet-spinning of 1D fibers and wet-spinning of continuous 2D films and 3D ultraflyweight aerogels. The thread of the research concepts is discussed to offer an overview of graphene macroscopic assembly. We summarize the fabrication system of wet-spinning of fiber and films, which extends to the chemistry of solvated graphene, the formation of graphene LCs, and the chemical/thermal reduction of graphene materials. The experimental details of graphene ultraflyweight aerogel are also been described. We hope that this paper can act as an experimental guidance for researchers, and become suggestive for forthcoming advances in graphene macroscopic materials. [ABSTRACT FROM AUTHOR]

We herein report the influences of chain orientation and packing on the photoluminescent (PL) and photothermal properties of polybenzimidazole fibers with meta-linkage under different excitation wavelengths (λex) and powers of laser sources. For the purpose, poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PmBI) was synthesized and then processed into fibers via solution spinning and heat treatment. The chain orientation and packing of the as-spun PmBI fiber decreased and increased owing to the heat treatment, respectively, which resulted from the nonlinear chain conformation of PmBI with meta-linkage. It was found that the visible PL intensity under λex = 325 nm, which is associated with an efficient interchain photorelaxation between benzimidazole rings, was much higher for the as-spun fiber with higher chain orientation, while the infrared PL intensity under λex = 514 nm, which is dominated by an intrachain photorelaxation, was far higher for the heat-treated fiber with higher chain packing. Accordingly, the heat-treated PmBI fiber exhibited excellent photothermal heating behavior by attaining maximum temperature increments (ΔTmax) of ~31.7 °C under λex = 405 nm and 18.4 mW, which was even higher than the as-spun fibers (ΔTmax ~ 27.5 °C). For the PmBI fibers, the ΔTmax values were also found to increase with the decrease of λex. [ABSTRACT FROM AUTHOR]

The present study describes a uniqueway of integrating substrateless electrospinning process with textiletechnology. We developed a new collector design that provided a pressure-driven,localized cotton-wool structure in free space from which continuoushigh strength yarns were drawn. An advantage of this integration wasthat the textile could be drug/dye loaded and be developed into acore–sheath architecture with greater functionality. This methodcould produce potential nanotextiles for various biomedical applications. [ABSTRACT FROM AUTHOR]

Dragline silk has been proposed tocontain two main protein constituents,MaSp1 and MaSp2. However, the mechanical properties of synthetic spidersilks spun from recombinant MaSp1 and MaSp2 proteins have yet to approachnatural fibers, implying the natural spinning dope is missing criticalfactors. Here we report the discovery of novel molecular constituentswithin the spinning dope that are extruded into dragline silk. Proteinstudies of the liquid spinning dope from the major ampullate gland,coupled with the analysis of dragline silk fibers using mass spectrometry,demonstrate the presence of a new family of low-molecular-weight cysteine-richproteins (CRPs) that colocalize with the MA fibroins. Expression ofthe CRP family members is linked to dragline silk production, specificallyMaSp1 and MaSp2 mRNA synthesis. Biochemical data support that CRPmolecules are secreted into the spinning dope and assembled into macromolecularcomplexes via disulfide bond linkages. Sequence analysis supportsthat CRP molecules share similarities to members that belong to thecystine slipknot superfamily, suggesting that these factors may haveevolved to increase fiber toughness by serving as molecular hubs thatdissipate large amounts of energy under stress. Collectively, ourfindings provide molecular details about the components of draglinesilk, providing new insight that will advance materials developmentof synthetic spider silk for industrial applications. [ABSTRACT FROM AUTHOR]

In the last years, there has been an increasing interest in bioinspired approaches for different applications, including the spinning of high performance silk fibers. Bioinspired spinning is based on the natural spinning system of spiders and worms and requires combining changes in the chemical environment of the proteins with the application of mechanical stresses. Here we present the novel straining flow spinning (SFS) process and prove its ability to produce high performance fibers under mild, environmentally friendly conditions, from aqueous protein dopes. SFS is shown to be an extremely versatile technique which allows controlling a large number of processing parameters. This ample set of parameters allows fine-tuning the microstructure and mechanical behavior of the fibers, which opens the possibility of adapting the fibers to their intended uses. [ABSTRACT FROM AUTHOR]