Wet Spinning Research Articles

High optical contrast, dual-responsive, wearable photochromic fibers for smart textile engineering

Smart textiles exhibiting responsiveness to external light stimuli show a great scope of applications in personalized decorations and intelligent wearable devices, among others. It's both rewarding and challenging to build wearable indicators based on fibers with high contrast and versatility to monitor the state of the external environment while maintaining good conformability and breathability for practical use. Here, we have integrated spiropyran photochromic compound (SP) into the spinning solution with polyvinyl alcohol (PVA) and aqueous polyurethane (WPU), and developed fibers by wet spinning featuring photochromic and photofluorescent dual outputs. Under UV and visible light illumination, the fibers demonstrate significant contrast optical signals, rapid color switching (4 s), long retention duration (7.5 h), as well as good cycling stability (20 times). The photochromic fibers can be used in the form of photochromic wristbands or embroidered on various textiles as flexible wearable UV indicators. Furthermore, the UV-induced fibers also produce pertinent color changes when subjected to acidic and alkaline vapors. We envision that the as-prepared fibers present promising applications in environmental acidity detection and multi-stimulus responsive materials.

Highly Conductive Double‐Wall Carbon Nanotube Fibers Produced by Dry‐Jet Wet Spinning

AbstractCarbon nanotube fibers (CNTFs) are considered an ideal candidate as next‐generation conducting wires due to their high conductivity and low density. However, the orientation and compaction of the nanotubes in a CNTF need to be further improved to achieve even higher conductivity and ampacity. Here the fabrication of double‐wall CNTFs (DWCNTFs) is reported by a dry‐jet wet spinning method, which significantly improves the orientation and compaction of the carbon nanotubes (CNTs). As a result, the obtained DWCNTFs have a record high electrical conductivity of 1.1 × 107 S m−1 and ampacity of 8.0 × 108 A m−2. The fibers also have a high tensile strength of 1.65 GPa and a toughness of 130.9 MJ m−3, among the highest for wet‐spun CNTFs. The DWCNTFs preserve their integrity and conductivity after more than 5000 bending cycles. Theoretical calculations indicate that in a dry‐jet wet‐spinning process, gravity promotes the orientation of the CNTs along the axial direction of the fiber.

Preparation of Meta-Aramid Filaments with High Strength and UV-Resistant Properties through Wet Spinning

Preparation of Meta-Aramid Filaments with High Strength and UV-Resistant Properties through Wet Spinning

Fabrication of Polymer/Cholesteric Liquid Crystal Films and Fibers Using the Nonsolvent and Phase Separation Method.

In recent years, liquid crystal materials have drawn great interest because of their wide range of applications. Among various thermochromic materials, cholesteric liquid crystalline (CLC) materials have been well studied and reported. CLC materials have the advantages of ready manipulation and multiple color transitions. For the further development of smart clothing and wearable electronics, however, the incorporation of CLC materials into polymers still remains challenging. The difficulties lie in the prevention of leakage of CLC and retention of the cholesteric liquid crystalline phase. In this work, we demonstrate a versatile nonsolvent and phase separation method using polar solvents to incorporate CLC microspheres into polymer matrix. Poly(vinyl alcohol) (PVA), a water-soluble polymer, is chosen as the polymer because of its high transparency and ease to handle. Using spin-coating and wet spinning techniques, PVA/CLC films and fibers can be fabricated. The formation of CLC microspheres in the polymer matrix is characterized through optical and polarized microscopy. Compared with the CLC films, the PVA/CLC composites demonstrate superior thermal stability. Moreover, both PVA/CLC films and fibers exhibit good color stability from the electrical tests. This work provides an effective strategy to prepare polymer/CLC composites, paving a wide avenue toward applications in smart textiles, display technologies, and medical devices.

Strong and Robust Core-Shell Ceramic Fibers Composed of Highly Compacted Nanoparticles for Multifunctional Electronic Skin.

Functional fibers composed of textiles are considered a promising platform for constructing electronic skin (e-skin). However, developing robust electronic fibers with integrated multiple functions remains a formidable task especially when a complex service environment is concerned. In this work, a continuous and controllable strategy is demonstrated to prepare e-skin-oriented ceramic fibers via coaxial wet spinning followed by cold isostatic pressing. The resulting core-shell structured fiber with tightly compacted Al-doped ZnO nanoparticles in the core and highly ordered aramid nanofibers in the shell exhibit excellent tensile strength (316MPa) with ultra-high elongation (33%). Benefiting from the susceptible contacts between conducting ceramic nanoparticles, the ceramic fiber shows both ultrahigh sensitivity (gauge factor = 2141) as a strain sensor and a broad working range up to 70 °C as a temperature sensor. Furthermore, the tunable core-shell structure of the fiber enables the optimization of impedance matching and attenuation of electromagnetic waves for the corresponding textile, resulting in a minimum reflection loss of -39.1dB and an effective absorption bandwidth covering the whole X-band. Therefore, the versatile core-shell ceramic fiber-derived textile can serve as a stealth e-skin for monitoring the motion and temperature of robots under harsh conditions.

Si@porous carbon fiber fabricated via wet spinning as a high-performance anode material for lithium-ion battery

Si/C composites are considered as attractive anode candidates for high-energy-density lithium-ion batteries and have been extensively researched. The carbon fiber (CF) fabricated by wet spinning is a well-established technology. However, there are scarce reports on Si/CF anodes fabricated by wet spinning. In this study, Si@porous carbon fiber (Si@PCF) composite were synthesized via wet spinning and subsequent thermal treatment. The porous carbon (PC) can effectively buffer the huge volume changes of Si nanoparticles during the charge-discharge process, promote the diffusion and transport of lithium ions, and compensate for the poor electronic conductivity of Si. The Si@PCF composite maintained a high capacity of 1178 mA h g−1 at 0.5 A g−1 after 100 cycles, suggesting potential for commercial application of the Si/PCF anode due to the excellent electrochemical performance and preparation technology suitable for large-scale production.

Continuous dual-network alginate hydrogel fibers with superior mechanical and electrical performance for flexible multi-functional sensors

Hydrogel fibers play a crucial role in the design and manufacturing of flexible electronic devices. However, continuous production of hydrogel fibers with high strength, toughness, and conductivity remains a significant challenge. In this study, ion-conductive sodium alginate/polyvinyl alcohol composite hydrogel fibers with an interlocked dual network structure were prepared through continuous wet spinning based on the pH-responsive dynamic borate ester bonds. Owing to the interlocked dual network structure, the resulting hydrogel fibers integrated superior performance of strength (4.31 MPa), elongation-at-break (>1500 %), ion conductivity (17.98 S m−1) and response sensitivity to strain (GF = 3.051). Benefiting from the excellent performance, the composite hydrogel fiber could be applied as motion-detecting sensors, including high-frequency, high-speed reciprocating mechanical motion, and human motion. Furthermore, the superior compatibility for human-computer interaction of the hydrogel fiber was also demonstrated, which a manipulator could be controlled to perform different actions, by a smart glove equipped with the hydrogel fiber sensors.

Circularly Polarized Room Temperature Phosphorescence through Twisting‐Induced Helical Structures from Polyvinyl Alcohol‐Based Fibers Containing Hydrogen‐Bonded Dyes

AbstractRoom temperature phosphorescence (RTP) materials have garnered significant attention owing to its distinctive optical characteristics and broad range of potential applications. However, the challenge remains in producing RTP materials with more simplicity, versatility, and practicality on a large scale, particularly in achieving chiral signals within a single system. Herein, we show that a straightforward and effective combination of wet spinning and twisting technique enables continuously fabricating RTP fibers with twisting‐induced helical chirality. By leveraging the hydrogen bonding interactions between polyvinyl alcohol (PVA) and quinoline derivatives, along with the rigid microenvironment provided by PVA chains, typically, Q‐NH2@PVA fiber demonstrates outstanding phosphorescent characteristics with RTP lifetime of 1.08 s and phosphorescence quantum yield of 24.6 %, and the improved tensile strength being 1.7 times than pure PVA fiber (172±5.82 vs 100±5.65 MPa). Impressively, the transformation from RTP to circularly polarized room temperature phosphorescence (CP‐RTP) is readily achieved by imparting left‐ or right‐hand helical structure through simply twisting, enabling large‐scale production of chiral Q‐NH2@PVA fiber with dissymmetry factor of 10−2. Besides, an array of displays and encryption patterns are crafted by weaving or seaming to exemplify the promising applications of these PVA‐based fibers with outstanding adaptivity in cutting‐edge anti‐counterfeiting technology.

Circularly Polarized Room Temperature Phosphorescence through Twisting-Induced Helical Structures from Polyvinyl Alcohol-Based Fibers Containing Hydrogen-Bonded Dyes.

Room temperature phosphorescence (RTP) materials have garnered significant attention owing to its distinctive optical characteristics and broad range of potential applications. However, the challenge remains in producing RTP materials with more simplicity, versatility, and practicality on a large scale, particularly in achieving chiral signals within a single system. Herein, we show that a straightforward and effective combination of wet spinning and twisting technique enables continuously fabricating RTP fibers with twisting-induced helical chirality. By leveraging the hydrogen bonding interactions between polyvinyl alcohol (PVA) and quinoline derivatives, along with the rigid microenvironment provided by PVA chains, typically, Q-NH2@PVA fiber demonstrates outstanding phosphorescent characteristics with RTP lifetime of 1.08 s and phosphorescence quantum yield of 24.6 %, and the improved tensile strength being 1.7 times than pure PVA fiber (172±5.82 vs 100±5.65 MPa). Impressively, the transformation from RTP to circularly polarized room temperature phosphorescence (CP-RTP) is readily achieved by imparting left- or right-hand helical structure through simply twisting, enabling large-scale production of chiral Q-NH2@PVA fiber with dissymmetry factor of 10-2. Besides, an array of displays and encryption patterns are crafted by weaving or seaming to exemplify the promising applications of these PVA-based fibers with outstanding adaptivity in cutting-edge anti-counterfeiting technology.

Fabrication of pressure visual fiber based on liquid metal control thermochromic pigments

AbstractIn this study, pressure visual fibers (PVF) with a core‐shell structure were prepared using a coaxial wet spinning process. The fiber composite shell consists of a luminescent material (as a light source) and a thermochromic pigment (as a filter light source) mixed with a polyacrylonitrile (PAN) matrix. The fiber core layer, on the other hand, was made of gallium‐indium alloy liquid metal. In operation, the filter light source is activated by joule heat drive (resulting in the fading of the thermochromic pigment), and the PVF releases phosphorescence upon exposure to ultraviolet light. When a certain pressure is applied to the fiber shell, the liquid metal in the core layer is squeezed, resulting in a local cross‐sectional area reduction, an increase in local joule thermal power, and thus local discoloration. This localized compression, in combination with a small rated current and the presence of an ultraviolet light source, converts the mechanical force (strain and compression) into an optical response. The excellent electrical conductivity of the liquid metal, combined with its compatibility with the soft matrix, makes it a promising candidate for applications in smart textiles and flexible sensing.Highlights The technology of visual fiber controlled by current is presented. The bendability and controllability of visual composites are improved. The composite fiber can be visualized when stressed.

Lead-rivet strategy of growing perovskite nanocrystals for excellent toxicity inhibition and spinning application

Lead halide perovskite has demonstrated remarkable potential in the wearable field due to its exceptional photoelectric conversion capability. However, its lead toxicity issue has consistently been subject to criticism, significantly impeding its practical application. To address this challenge, an innovative approach called lead-rivet was proposed for the in-situ growth of perovskite crystalline structures. Through the formation of S-Pb bonds, each Pb2+ ion was firmly immobilized on the surface of the silica matrix, enabling in situ growth of perovskite nanocrystals via ion coordination between Cs+ and halide species. The robust S-Pb bonding effectively restricted the mobility of lead ions and stabilized the perovskite structure without relying on surface ligands, thereby not only preventing toxicity leakage but also providing a favorable interface for depositing protective shells. The obtained perovskites exhibit intense and narrow-band fluorescence with full-width at half-maximum less than 23 nm and show excellent stability to high temperature (above 202 °C) and high humidity (water immersion over 27 days), thus making it possible to be used in varies textile technologies including melt spinning and wet spinning. The lead leakage rate of particles is only 4.15 % demonstrating excellent toxicity inhibition performance. The prepared fibers maintained good extensibility and flexibility which could be used for 3D-printing and textiles weaving. Most importantly, the detected Pb2+ leaching was negligible as low as to 0.732 ppb which meet the standard of World Health Organization (WHO) for drinking water (<10 ppb), and the cell survival rate remained 99.196 % for PLA fluorescent filament after 24 h cultivation which showing excellent safety to human body and environment. This study establishes a controllable and highly adaptable synthesis method, thereby providing a promising avenue for the safe utilization of perovskite materials.

Modulating oxygen vacancies in MXene/MoO3-x smart fiber by defect engineering for ultrahigh volumetric energy density supercapacitors and wearable SERS sensors

MXene fibers are expected to accelerate the sustainable development of intelligent era as multi-functional smart fibers. However, MXene fibers have serious obstacles when used for multi-functional applications. Here, we fabricated a multi-functional MXene fiber by incorporating MoO3-x nanobelts with abundant oxygen vacancies via wet spinning and defect engineering methods. Benefiting from the presence of abundant oxygen vacancies, the produced MXene/MoO3-x fibers not only provide more active sites to interact with electrolyte ions, but also substantially augment the rate capacities of fibers due to the enlarged distances between MXene flakes. Thus, the assembled fiber-based supercapacitor (SCs) realized high capacitance of 869.1F cm−3 at 0.5 A cm−3, good volumetric energy density of 77.3 mWh cm−3 at a power density of 204.8 mW cm−3 and long-term cycling stability along with 86.4 % capacity retention after 5000 cycles. Moreover, due to the narrowed bandgap of MoO3-x produced by defect engineering enhanced the charge transfer between the fiber and molecules, MXene/MoO3-x fiber also demonstrated a low limit of detection and reliable biomarkers detection in artificial sweat. These findings provide the potential application of MXene-based fibers in multi-functional devices.

Effects of polyvinylpyrrolidone additive on structures and properties of Poly(m-phenylene isophthalamide) hollow fiber membranes -experiment observation and computation approach

This study systematically investigates the effect of introduction of polyvinylpyrrolidone (PVP) used as a hydrophilic additive and its molecular weight change on the morphological, mechanical properties, and membrane performances of poly(m-phenylene isophthalamide) (PMIA) hollow fiber (HF) membranes prepared by dry-jet wet spinning method. The results of the morphological and mechanical properties clearly show an increased proportion of a sponge-like pore structure and an overall improvement in the mechanical properties of the PMIA HF membranes with higher molecular weight PVP, respectively. Interestingly, molecular dynamics simulation showed that the presence of PVP within the PMIA matrix activated the overall movement of PMIA molecules, suggesting that the overall flexibility of the system, which can potentially inhibit the collapse of relatively brittle membranes, is increased by the presence of PVP. Finally, as the molecular weight of PVP increases, a typical trade-off phenomenon is observed on PMIA HF membranes, where the water permeability decreases while the rejection rate increases. Based on these results, the findings on the influence of PVP additive and its potential as a reinforcing agent observed in this study through experimental analysis and computational approaches are expected to provide new insights into the development of high-performance polymeric HF membranes.

Wet-Spinning Preparation of High-Performance Phenol-Modified Melamine-Formaldehyde Fibers

In order to improve the toughness of melamine formaldehyde (MF) fibers, the modified fibers with varying synthesis mole ratios were fabricated through wet spinning utilizing melamine and paraformaldehyde as the primary constituents and phenol as the modifying agent. The structural characteristics and properties of the fibers were assessed and examined through Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mechanical property evaluations. The results showed that the incorporation of phenol led to a significant enhancement in both the thermal stability and mechanical properties of the fibers. Specifically, when the mole ratio of melamine, phenol, and paraformaldehyde was 1:1:4 and the heat curing temperature was 180 °C, the fiber exhibited a breaking strength of 151 MPa and an elongation at break of 15.1%. This represented an increase in elongation at break of approximately 84% compared to the unmodified fiber without phenol. Furthermore, the thermal properties of the modified fibers were notably improved, as evidenced by an increase in char yield at 700 °C from 27.7% to 62.5%.

A A Novel Poly (vinylidene) Fluoride/TiO2/Spent Bleaching Earth for Enhancing Hydrophilic Hollow Fibre Membrane

Nowadays, polymer as the raw material has been utilized in the development of Hollow Fibre (HF) membranes. PVDF is a commonly used for HF membrane material. However, it has hydrophobicity properties and lead membrane becomes low permeability and fouling. Therefore, to avoid these membranes problems, the incorporation of inorganic nanoparticles into PVDF membranes matrix is necessary to be applied for significantly improving PVDF membranes performance. This study investigates the characteristics and performance of PVDF-TiO2 HF membranes using spent bleaching earth (SBE) as a promising material from industrial waste as a renewable inorganic nanoparticle. This novel PVDF-TiO2-SBE HF membrane was fabricated using the subsequent steps: The preparation process incorporates SBE revival through solvent extraction and thermal treatment alongside the wet spinning technique for membrane fabrication. The Fourier transform infrared (FTIR) functional groups, scanning electron microscope (SEM) morphology, water contact angle and pure water flux performance were investigated to specifically understand the performance of this typical HF membranes. The IR results show that Si-O-Si groups were found in the membrane matrices due to the addition of SBE material. The addition of TiO2-SBE particles also indicate a sandwich (sponge-finger-like) morphological structure on the cross-sectional, a rough and porous surface structures. The hydrophilic properties of the HF membrane and pure water flux performance are determined by the composition of the TiO2-SBE mixture added as an additive material. The minimum contact angle found at 74.33°, while the water flux is 5.81 kg.m-2.h-1 on the identical HF membrane. Accordingly, this approach significantly enhances the properties of the pure PVDF HF membrane.

A PEDOT: PSS/GO fiber microelectrode fabricated by microfluidic spinning for dopamine detection in human serum and PC12 cells.

Rapid and accurate in situ determinationof dopamine is of great significance in the study of neurological diseases. In this work, poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid) (PEDOT: PSS)/graphene oxide (GO) fibers were fabricated by an effective method based on microfluidic wet spinning technology. The composite microfibers with stratified and dense arrangement were continuously prepared by injecting PEDOT: PSS and GO dispersion solutions into a microfluidic chip. PEDOT: PSS/GO fiber microelectrodes with high electrochemical activity and enhanced electrochemical oxidation activity of dopamine were constructed by controlling the structure composition of the microfibers with varying flow rate. The fabricated fiber microelectrode had a low detection limit (4.56 nM) and wide detection range (0.01-8.0 µM) for dopamine detection with excellent stability, repeatability, and reproducibility. In addition, the PEDOT: PSS/GO fiber microelectrode prepared was successfully used for the detection of dopamine in human serum and PC12 cells. The strategy for the fabrication of multi-component fiber microelectrodes isa new and effective approach for monitoring the intercellular neurotransmitter dopamine and has highpotential as an implantable neural microelectrode.

Low flow-resistance solid phase extraction of fluoroquinolones in water and food samples by high-pressure wet spinning porous polyimide microfibers

In this work, porous polyimide microfibers (PI-μF) were prepared by high-pressure wet spinning method, and successfully applied as adsorbents for solid phase extraction (SPE) of fluoroquinolones (FQs) in water and food samples. The PI-μFs of ∼10, 25, 50, 100 μm in diameter could be controlled by the inner diameter of quartz capillary nozzles. The flow resistance of SPE cartridges packed with 10 μm PI microfiber (10-PI-μF) and 25-PI-μF was comparable to or even lower than that of commercial SPE cartridges, while the flow resistance of 50-PI-μF and 100-PI-μF SPE cartridges was increased obviously due to tiny broken pieces. The 10-PI-μF and 25-PI-μF have a specific surface area of 102 m2 g−1 and 76 m2 g−1, mesopores of 22–32 nm, and large breakthrough volume of 110 mL/5 mg and 85 mL/5 mg for FQs, while the 50-PI-μF and 100-PI-μF had much lower specific surface area and hardly had retention for FQs. FQs from tap water, egg and milk samples were then extracted by PI-μF SPE, and analyzed by high performance liquid chromatography-fluorescence detector (HPLC-FLD). SPE parameters as type of elution solvent, elution solvent volume, pH value of sample solution, flow rate of sample solution, and breakthrough volume were first optimized in detail. Under the optimal conditions, the PI-μF SPE/HPLC-FLD method showed high recoveries (96.8%–107%), wide linearity (0.05–50 μg L−1, or 0.01–10 μg L−1), high determination coefficients (R2 ≥0.9992), and low limits of detection (LODs, 0.005–0.014 μg L−1). For the real tap water, egg and milk samples, the recoveries and RSDs were 81–119% and 0.8–9.8%, respectively. The results show that porous microfiber up to 25 μm in diameter is a promising solid-phase extraction adsorbent with the lowest flow resistance that can be used for trace organic pollutants in water and food samples.

Polyacrylonitrile In-Situ reinforced polyimide superhydrophobic porous fibers: A miraculous thermal insulation and flame-retardant material

In response to the demand for safety protective textiles suitable for extreme conditions such as intense heat and humidity, we have innovatively developed a novel approach using polyacrylonitrile (PAN) in-situ reinforced polyimide (PI) superhydrophobic porous fibers. We blended fluorinated polyamic acid (PAA) with PAN and prepared PI/pre-oxidized fiber (panof) porous fibers using a process that includes wet phase separation spinning and integrated synchronous imidization/pre-oxidation. Special emphasis was placed on the chemical mechanisms during the heat treatment stage of the preparation process. The uncapped PAA underwent imidization reactions and also facilitated PAN’s pre-oxidation, which notably enhanced the structural stability of the PI porous fibers. This novel enhancement mechanism effectively addresses the challenges of structural collapse and volume shrinkage encountered in the preparation of traditional PI porous fibers. In addition, our investigation into the impact of thermal imidization temperature on the structure of porous fibers led to the evaluation of PI/panof porous fibers. The PI/panof-320 porous fibers, produced by the combined enhancement effect of fluorinated PI and PAN, showcased exceptional features: superhydrophobicity (water contact angle = 168.9°), low density (0.078 g/cm3), reduced thermal conductivity (0.0251 W/(m·K)), high strength (22.18 MPa), outstanding flexibility (bend radius = 205 μm), and superior flame retardancy and insulation. The outstanding performance of these composite porous fibers paves the way for innovative, comfortable, and safe wearable devices in high heat and humidity environments, highlighting their extensive applicability and potential.

Core–Shell Bacterial Cellulose/Graphene Oxide@Polydopamine Aerogel Fibers for Personal Thermal Management Textiles

AbstractThe porous nature and gel network of aerogel fibers make them ideal options for personal thermal management because they can significantly cut down on energy waste. However, aerogel fibers generally suffer from poor mechanical properties and single function. Herein, the porous continuous bacterial cellulose/graphene oxide@polydopamine core–shell aerogel fibers with high strength, excellent photothermal properties, and thermal insulation are investigated by wet spinning and freeze‐drying. The bacterial cellulose/graphene oxide@polydopamine aerogel fiber prepared by wet spinning method has a porous structure, which can prevent heat convection, reduce heat conduction, and suppress heat radiation, making the aerogel fiber have excellent thermal insulation properties. More crucially, graphene oxide may considerably enhance infrared radiation's capacity for heating, while polydopamine can enhance ultraviolet light absorption and boost photothermal conversion capability.

High-speed spinning of collagen microfibers comprising aligned fibrils for creating artificial tendons

Bundles of engineered collagen microfibers are promising synthetic tendons as substitutes for autogenous grafts. The purpose of this study was to develop high-speed and continuous spinning of collagen microfibers that involves stretching of collagen stream. Our study revealed the ‘critical fibrillogenesis concentration (CFC)’ of neutralized collagen solutions, which is defined as the upper limit of the collagen concentration at which neutralized collagen molecules remain stable as long as they are cooled ( ⩽ 10 °C). Neutralized collagen solutions at collagen concentrations slightly below the CFC formed cord-like collagen gels comprising longitudinally aligned fibrils when extruded from nozzles into an ethanol bath. Dry collagen microfibers with a controlled diameter ranging from 122 ± 2–31.2 ± 1.7 μm can be spun from the cord-like gels using nozzles of various sizes. The spinning process was improved by including stretching of collagen stream to further reduce diameter and increase linear velocity. We extruded a collagen solution through a 182 μm diameter nozzle while simultaneously stretching it in an ethanol bath during gelation and fiber formation. This process resembles the stretching of a melted thermoplastic resin because it solidifies during melt spinning. The mechanical properties of the stretched collagen microfibers were comparable to the highest literature values obtained using microfluidic wet spinning, as they exhibited longitudinally aligned fibrils both on their surface and in their core. Previous wet spinning methods were unable to generate collagen microfibers with a consistent tendon-like fibrillar arrangement throughout the samples. Although the tangent modulus (137 ± 7 MPa) and stress at break of the swollen bundles of stretched microfibers (13.8 ± 1.9 MPa) were lower than those of human anterior cruciate ligament, they were within the same order of magnitude. We developed a spinning technique that produces narrow collagen microfibers with a tendon-like arrangement that can serve as artificial fiber units for collagen-based synthetic tendons.