Search Results (156)

Carbon layer-coated μm-sized carbon fiber has the potential to be developed as an electrode, as it can be directly used as an electrode without any preparation process in the absence of an insulating binder. In our work, a carbon layer-coated carbon fiber (C@CF) coaxial structure is constructed by in situ conversion of the epoxy resin around the carbon fiber into a carbon layer, in which a sandwich scaffold of cover/CFRP/screen is designed and adopted. The activated SC@CF, i.e., A-SC@CF, can be directly served as the electrode, and has excellent supercapacitor performance: a high specific capacity of 227.1 F g⁻¹ at 0.5 A g⁻¹, with a capacitance retention of 98.9% after 20,000 cycles for the electrode, and an energy density of 16.68 Wh kg⁻¹ at the power density of 1400 W kg⁻¹ for its symmetrical supercapacitor (SSC). Full article

The laser heterogeneous lap welding of nickel-plated steel and Cu sheets has been investigated in this study. The YAG (Yttrium-Aluminum-Garnet) laser beam only penetrates the upper Ni-plated steel sheet and cannot weld the bottom Cu sheet due to the low absorption coefficient of the YAG laser beam. Incorporating a blue-light and fiber laser into the coaxial laser beam significantly improves the quality of the weld fusion zone. The fiber laser beam can penetrate the upper nickel-plated steel sheet, and the blue-light laser beam can melt the bottom copper sheet. Introducing the blue-light laser to the coaxial laser beams overcomes the low reflectivity of the bottom copper sheet. The fiber/blue-light coaxial laser continuous welding can achieve the best integrity and defect-free welding. It shows potential in the mass production of the next generation of lithium batteries. Full article

Dicyclopentadiene (DCPD)–poly(methyl methacrylate) (PMMA) core–shell fibers were fabricated via coaxial electrospinning to develop a self-healing polymer composite. A PMMA shell containing a first-generation Grubbs catalyst was co-spun with a DCPD core at 0.5 mL h⁻¹ and 28 kV, yielding smooth, cylindrical fibers. The diameter range of nanofibers was 300–900 nm, with 95% below 800 nm, as confirmed by FESEM image analysis. FTIR spectroscopy monitored shell integrity via the PMMA C=O stretch and core polymerization via the trans-C=C bands. The high presence of the 970 cm⁻¹ band in the healed nanofiber mat and the minor appearance in the uncut core–shell mat demonstrated successful DCPD polymerization mostly where the intended damage was. The optical clarity of PMMA enabled the direct monitoring of healing progress via optical microscopy. The presented findings demonstrate that PMMA can retain a liquid active core and catalyst to form a polymer layer on a damaged site and could be used as a model material for other self-healing systems that require healing monitoring. Full article

The electrospinning technique can produce multifunctional polymeric devices by forming solid fibers from polymer solutions under a high-voltage electric field. Variations such as concentric needles yield core/shell fibers. This study evaluates the effects of applied voltage (12.5–20 kV) and tip-to-collector distance (12.5–20 cm) on the morphology and thermochemical behavior of PLGA/PVA fibers made by coaxial electrospinning compared with casting-produced membranes and monolithic fibers. Optimal coaxial fibers (597 ± 90 nm diameter) were produced at 15 cm/12.5 kV, exhibiting a well-defined core/shell structure (PVA core: ~100 nm; PLGA shell: ~50 nm) confirmed by laser scanning confocal (core solution labeled with fluorescein) and TEM. FTIR and TGA demonstrated nearly complete solvent removal in electrospun samples versus ~10% solvent retention in cast films. XRD analysis indicated that cast films (PLGAff) exhibited minimal crystallinity (Xc ≈ 0.1%), while electrospun PLGA (PLGAe) showed cold crystallization and higher crystallinity (Tcc ≈ 90.6 °C; Xc ≈ 2.45%). DSC detected two different Tg (≈43.2 °C and 52.8 °C) in the coaxial fibers, confirming distinct polymer domains with interfacial interactions. These results establish precise processing/structure relationships for defect-free coaxial fibers and provide fundamental design principles for hybrid systems in controlled drug delivery and tissue engineering applications. Full article

In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two concentration levels. The system implemented to perform the spinning was a coaxial setup in which the internal flow contains the precursor dispersion with the metallic precursor, and ethanol was used as external flow to help fiber formation and prevent drying before generating the Taylor cone. The obtained cloths were thermostabilized in air at 200 °C and carbonized in nitrogen at 900 °C. The resulting carbon fibers were characterized by physicochemical and electrochemical techniques. The palladium precursor significantly affects nanoparticle distribution and size, fiber diameter, pore distribution, surface area and electrochemical behavior. The fibers prepared with palladium acetylacetonate at high Pd loading and carbonized at 900 °C under a CO₂ atmosphere showed high mechanical stability and the best ORR activity, showing near total selectivity towards the 4-electron path. These features are comparable to those of the commercial Pt/C catalyst but much lower metal loading (10.6 wt.% vs. 20 wt.%). The most promising fibers have been evaluated as cathodes in a zinc–air battery, delivering astonishing stability results that surpassed the performance of commercial Pt/C materials in both charging and discharging processes. Full article

Gene therapy, which treats genetic diseases by fixing defective genes, has gained significant attention. Viral vectors show great potential for gene delivery but face limitations like poor targeting, uncontrolled release, and risks from high-dose delivery which can lower efficiency and trigger immune responses. Loading viral vectors onto tissue engineered scaffolds presents a promising strategy to address these challenges, but their widespread application remains limited due to concerns regarding viral vector bioactivity, scaffold biocompatibility, and the stability of sustained release. An adeno-associated virus (AAV), recognized for its safety, high efficiency, and low immunogenicity, was employed as a model virus. In this study, we developed an electrospun scaffold (AAV/PCL-PEO@Co-ES) by encapsulating the AAV within core–shell fibers composed of polycaprolactone (PCL) and polyethylene oxide (PEO) via coaxial electrospinning. This configuration ensures viral vector protection while enabling controlled and sustained release. The physicochemical characterization results indicated that the scaffold exhibited excellent mechanical properties (tensile strength: 3.22 ± 0.48 MPa) and wettability (WCA: 67.90 ± 8.45°). In vitro release and cell transduction assays demonstrated that the AAV-loaded scaffold effectively controls viral vector release and transduction. Furthermore, both in vitro and in vivo evaluations demonstrated good biocompatibility and efficient viral vector delivery. These findings highlight the potential of the AAV/PCL-PEO@Co-ES scaffold as a safe and effective platform for sustained gene delivery, offering valuable insights for the future design of clinically relevant viral vector delivery systems. Full article

Energy storage technologies, particularly those utilizing phase change materials (PCMs), have gained attention for their high energy density and efficient thermal management. PCMs, which store energy through solid-liquid phase transitions, can efficiently capture and release thermal energy, but face the challenge of leakage during the phase change process. Inorganic PCMs, such as salt hydrates, offer high energy storage capacity, but are difficult to encapsulate due to their corrosive nature. Conventional encapsulation techniques for inorganic PCMs are limited, particularly for scalable applications. In this work, we present an innovative method for the encapsulation of salt hydrate-based inorganic PCMs (CaCl₂·6H₂O) using co-axial electrospinning. The process involves the creation of co-axial fibers, with salt hydrate as the core and polymer (e.g., PVP) as the outer shell, effectively preventing leakage and improving the stability of the PCM. This approach demonstrates the potential for scalable microencapsulation of inorganic PCMs, marking the first report of using co-axial electrospinning for this purpose. This novel technique could contribute to enhancing the performance and applicability of PCMs in thermal energy storage systems and other energy efficiency applications. Full article

Composites of ferromagnetic and ferroelectric phases are of interest for studies on mechanical strain-mediated coupling between the two phases and for a variety of applications in sensors, energy harvesting, and high-frequency devices. Nanocomposites are of particular importance since their surface area-to-volume ratio, a key factor that determines the strength of magneto-electric (ME) coupling, is much higher than for bulk or thin-film composites. Core–shell nano- and microcomposites of the ferroic phases are the preferred structures, since they are free of any clamping due to substrates that are present in nanobilayers or nanopillars on a substrate. This review concerns recent efforts on ME coupling in coaxial fibers of spinel or hexagonal ferrites for the magnetic phase and PZT or barium titanate for the ferroelectric phase. Several recent studies on the synthesis and ME measurements of fibers with nickel ferrite, nickel zinc ferrite, or cobalt ferrite for the spinel ferrite and M-, Y-, and W-types for the hexagonal ferrites were considered. Fibers synthesized by electrospinning were found to be free of impurity phases and had uniform core and shell structures. Piezo force microscopy (PFM) and scanning microwave microscopy (SMM) measurements of strengths of direct and converse ME effects on individual fibers showed evidence for strong coupling. Results of low-frequency ME voltage coefficient and magneto-dielectric effects on 2D and 3D films of the fibers assembled in a magnetic field, however, were indicative of ME couplings that were weaker than in bulk or thick-film composites. A strong ME interaction was only evident from data on magnetic field-induced variations in the remnant ferroelectric polarization in the discs of the fibers. Follow-up efforts aimed at further enhancement in the strengths of ME coupling in core–shell composites are also discussed in this review. Full article

We present the design and manufacturing of a deployable conical log spiral spring antenna for small spacecraft, along with a test campaign to evaluate its suitability for space applications. The conical spring was 45.7 cm in height, with base and apex diameters of 18.9 and 2.8 cm, respectively. The spring had a mass of 0.138 kg and was constructed from a carbon fiber-infused epoxy matrix with an embedded coaxial cable. We conducted dynamic and thermal mechanical analysis to determine the coefficient of thermal expansion and glass transition temperature. The initial 10 compressions of the spring shortened the structure’s overall height, but the change had a negligible effect on the antenna’s radio frequency (RF) performance. Thermal cycling between −70 °C and 80 °C did not cause any damage or deformation to the spring structure. Outgassing tests were conducted in a thermal vacuum chamber, and the total mass loss was 0.03%. We conducted vibration tests representative for a typical launch vehicle, and all natural frequencies remained stable above 250 Hz, while the antenna was stowed, satisfying launch vehicle requirements. Post-test functional checks confirmed that there was no change in antenna functionality. The environmental test results provide confidence that the antenna is suitable for spacecraft applications. Full article

In electrospun scaffolds, coaxial electrospinning is gaining increased attention due to its potential for biocomponent encapsulation and controlled delivery. However, the encapsulation of biocomponents, such as liposomes, remains challenging because of their low stability in commonly used electrospinning solvents. This study, therefore, aims to develop a novel coaxial electrospinning formulation for crafting a liposome-encapsulated, rapid-release coaxial fiber. Liposomes demonstrated desirable stability in fish gelatin/phosphate-buffered saline (PBS) solutions, which remain liquid at room temperature and exhibit exceptional spinnability at concentrations exceeding 80 w/v% due to the reduction in surface tension. Fluorescent labelling examinations confirmed the successful encapsulation of liposomes within coaxial fibers electrospun from a 160 w/v% gelatin/PBS core and a 20 w/v% PCL/chloroform/N,N-dimethylformamide (DMF) shell. The gelatin/PBS core solution formed solid ends at the tips of the core-shell fiber post-spinning, while maintaining a liquid state within the shell, thereby enabling the encapsulation of liposomes within the PCL coaxial fiber. Upon exposure to medium, the solid ends dissolve, enabling the rapid release of liposomes. The successful development of this liposome-loaded electrospun coaxial fiber, using fish gelatin, highlights its potential for creating advanced liposome delivery systems. Full article

An ultra-high-frequency (UHF) deployable conical log spiral antenna’s design and experimental test results are presented. The antenna is a spring constructed from a carbon-fiber-infused epoxy matrix. The spring design simplified the spacecraft deployment mechanism, and the use of composite materials allowed for the integration of radiating elements into the spring structure. A Chebyshev transformer at the base of the antenna is used to match the incoming transmission line impedance to a 95 $\mathrm{\Omega }$ coaxial cable. The 95 $\mathrm{\Omega }$ coaxial, which is the balun and the radiating element, is embedded into the antenna structure. The antenna is fed at the cone’s base without requiring a ground plane whilst maintaining radiation in the cone’s apex-pointing direction. This facilitated an uncomplicated deployment mechanism. Prototypes have been manufactured for 500 to 1500 MHz designs. Antenna measurements show a realized gain of between approximately 3 to 6 dBi from 500 to 1500 MHz. Full article

Cisplatin, a frequently used chemotherapeutic for the treatment of cervical cancer, causes adverse effects that limit its use. Treatment with local therapy that limits toxicity remains a challenge. The aim of this study was to develop a local intravaginal cisplatin delivery system of polycaprolactone/polyvinylpyrrolidone sheath/core fibers by coaxial electrospinning. Physicochemical properties, degradation rate, mucoadhesion, release profile, and in vitro biosafety assays were characterized. Microscopy images confirmed the coaxial nature of the fibers and showed continuous morphology and diameters of 3–9 µm. The combination of polymers improved their mechanical properties. The contact angle < 85° indicated a hydrophilic surface, which would allow its dissolution in the vaginal environment. The release profile showed a rapid initial release followed by a slow and sustained release over eight days. The degradation test showed ~50% dissolution of the fibers on day 10. The adhesion of the fibrous device to the vaginal wall lasted for more than 15 days, which was sufficient time to allow the release of cisplatin. The biosafety tests showed great cytocompatibility and no hemolysis. The characteristics of the developed system open the possibility of its application as a localized therapy against cervical cancer, reducing adverse effects and improving the quality of life of patients. Full article

Gas-assisted coaxial electrospinning (GACES) is a simple and general method for the mass preparation of coaxial nanofiber membranes, which has great industrial potential. However, in the manufacturing process, due to the bending instability of the jet in the electric field and the pulling effect of the gas flow field, the deposition uniformity of the fiber is still a big problem. Through finite element simulation analysis of the flow field in the manufacturing process and the construction of the jet mechanics model after adding the flow field, the influence mechanism of coaxial auxiliary flow on the fiber deposition area and its uniformity was successfully revealed in this research. Finally, the deposition area and thickness uniformity of coaxial fibers are increased by 3 times (the deposition area: 19.63 cm² → 78.50 cm²) and 2.34 times (the standard variance: 3 μm² → 10 μm²) by gas-assisted coaxial electrospinning. At the same time, the coaxial auxiliary gas flow also reduces the coaxial fiber diameter by 36.9% (the average fiber diameter: 241 nm ± 5 nm → 152 nm ± 23 nm) and the distribution range by 66% (the standard variance: 1.5 × 10² nm² → 51 nm²). This research provides a reliable idea and experimental basis for homogeneous preparation of coaxial nanofiber membranes. Full article

Distributed strain sensing is a powerful tool for in situ structural health monitoring for a wide range of critical engineering infrastructures. Strain information from a single sensing device can be captured from multiple locations simultaneously, offering a reduction in hardware, wiring, installation costs, and signal analysis complexity. Fiber optic distributed strain sensors have been the widely adopted approach in this field, but their use is limited to lower strain applications due to the fragile nature of silica fiber. Coaxial cable sensors offer a robust structure that can be adapted into a distributed strain sensor. They can withstand greater strain events and offer greater resilience in harsh environments. This paper presents the developments in methodology for coaxial cable distributed strain sensors. It explores the two main approaches of coaxial cable distributed strain sensing such as time domain reflectometry and frequency domain reflectometry with applications. Furthermore, this paper highlights further areas of research challenges in this field, such as the deconvolution of strain and temperature effects from coaxial cable distributed strain sensor measurements, mitigating the effect of dielectric permittivity on the accuracy of strain measurements, addressing manufacturing challenges with the partial reflectors for a robust coaxial cable sensor, and the adoption of data-driven analysis techniques for interrogating the interferogram to eliminate concomitant measurement effects with respect to temperature, dielectric permittivity, and signal-to-noise ratio, amongst others Full article

The transient electroosmotic response in a charged porous medium consisting of a uniform array of parallel circular cylindrical fibers with arbitrary electric double layers filled with an electrolyte solution, for the stepwise application of a transverse electric field, is analyzed. The fluid momentum conservation equation is solved for each cell by using a unit cell model, where a single cylinder is surrounded by a coaxial shell of the electrolyte solution. A closed-form expression for the transient electroosmotic velocity of the bulk fluid in the Laplace transform is obtained as a function of the ratio of the cylinder radius to the Debye screening length and the porosity of the fiber matrix. The effect of the fiber matrix porosity on the continuous growth of the electroosmotic velocity over time is substantial and complicated. For a fiber matrix with larger porosity, the bulk fluid velocity takes longer to reach a certain percentage of its final value. Although the final value of the bulk fluid velocity generally increases with increasing porosity, early velocities may decrease with increasing porosity. For a given fiber matrix porosity, the transient electroosmotic velocity is a monotonically increasing function of the ratio of the cylinder radius to the Debye length. Full article