Flexible Fiber Research Articles

Exciton Dissociation and Recombination Afford Narrowband Organic Afterglow Through Efficient FRET.

Organic afterglow with long-persistent luminescence (LPL) after photoexcitation is highly attractive, but the realization of narrowband afterglow with small full-width at half-maximum (FWHM) is a huge challenge since it is intrinsically contradictory to the triplet- and solid-state emission nature of organic afterglow. Here, narrow-band, long-lived, and full-color organic LPL is realized by isolating multi-resonant thermally activated delayed fluorescent (MR-TADF) fluorophores in a glassy steroid-type host through a facile melt-cooling treatment. Such prepared host becomes capable of exciton dissociation and recombination (EDR) upon photoirradiation for both long-lived fluorescence and phosphorescence; and, the efficient Förster resonance energy transfer (FRET) from the host to various MR-TADF emitters leads to high-performance LPL, exhibiting small FWHM of 33nm, long persistent time over 10s, and facile color-tuning in a wide range from deep-blue to orange (414-600nm). Moreover, with the extraordinary narrowband LPL and easy processability of the material, centimeter-scale flexible optical waveguide fibers and integrated FWHM/color/lifetime-resolved multilevel encryption/decryption devices have been designed and fabricated. This novel EDR and singlet/triplet-to-singlet FRET strategy to achieve excellent LPL performances illustrates a promising way for constructing flexible organic afterglow with easy preparation methods, shedding valuable scientific insights into the design of narrow-band emission in organic afterglow.

Multistage rigid and flexible structure-decorated basalt fibers for epoxy resin composites with synergistically enhanced strength and toughness

In this study, we report the construction of a multistage rigid and flexible structure using boron nitride (BN) and MXene (MX, Ti3C2Tx) nanosheets through the conjugation with (3-aminopropyl) triethoxysilane (APTES). The created structure is further utilized to modify basalt fibers (BFs) to obtain BF/epoxy resin (BF/EP) composites via a simple coating process. The rigid two-dimensional materials (2DMs), BN and MX, significantly enhance the roughness of the BF surface, while the silane (APTES) acts as a flexible bridge for linking BFs, BN, and MX. Consequently, the constructed multistage rigid and flexible structure synergistically enhances the strength and toughness of the composite through effective mechanical interlocking, chemical bonding, and multistage energy dissipation. Meanwhile, this complex structure prevents the stress concentration and promotes uniform stress transfer between BFs and EP. This study provides a promising strategy to construct an effective interface layer and achieve high-performance BF/EP composites by introducing 2DMs and a silane linker.

Rheology of flexible fiber-reinforced cement pastes: Maximum packing fraction determination and structural build-up analysis

The maximum packing fraction (φfm) of flexible fibers is an essential parameter for understanding the rheological behavior of flexible fiber-reinforced cement paste (FFRCP). However, direct measurement of φfm of flexible fibers is still lacking. In this study, a shear rheology-based method for direct measurement of φfm was proposed and the assumption of fiber conformation under shear was verified by micro-CT. Based on this, a yield stress model for FFRCP was constructed to explain the entanglement and friction effects in the fiber network. Finally, static yield stress tests and small amplitude oscillatory shear (SAOS) tests were carried out to explore the structural build-up of FFRCP. It was found that the proposed method enables direct determination of φfm through only a few viscosity-fiber content data for a given FFRCP. Furthermore, the proposed model can describe the static yield stress of FFRCP well. Finally, the relative structural build-up rate of FFRCP follows a similar trend as the relative yield stress, with a critical relative fiber volume fraction (0.299) as the boundary. Subsequently, the relative structural build-up gradually deviates from the relative yield stress due to the limiting effect of the fibers.

Chinese ink-coated elastic PU/PET fibers as multifunctional flexible wearable sensors

Textiles as conductive substrates are widely used in sensing applications due to their good elasticity, high stretchability and recoverable deformation. Here, the mask rope (polyurethane/polyester blended fibers) was selected as flexible substrate to load of conductive Chinese ink using surface swelling technique in N, N-dimethylformamide. The presence of carbon nanoparticles in the ink imparts electrical conductivity to the elastic fiber while maintaining the mechanical properties and extensibility of the fiber. This simple and low-cost method allows excellent interfacial adhesion between the conductivity ink layer and the elastic fibers, and the carbon particles do not fall off even when the modified fiber was treated by sonication in water. The ink coated elastic fiber as strain sensor shows excellent stability and sensitive responsiveness after 500 stretch-release cycles. The response and recovery times during the sensitivity experiment of the flexible fiber sensor are 133.79 and 134.76 ms. The sensor exhibits physiological motion detection and quality monitoring capabilities, which can accurately monitor human movements such as walking, wrist movement, throat swallowing and articulation. The sensor also has a good Joule heating effect, and the temperature of the conductive fiber can increase 88.9°C in the 60s under 15V voltage. This work develops a simple and efficient, low-cost, mass-producible flexible sensor with potential for physiological activity, temperature, and humidity detection.

Preparation and Properties of Carbon Fiber/Flexible Graphite Composite Grounding Material

In this paper, flexible conductive composite materials were prepared from flexible graphite and carbon fiber by mould pressing, and their micromorphology was studied by SEM. The influence of carbon fiber content on the mechanical properties and electrical conductivity of the flexible conductive composite material was studied, and the corrosion rate of the flexible conductive composite material coupling with galvanized steel in soil with different SO42− concentrations was studied. The results showed that the tensile strength reached 5.82 MPa when the mass ratio of carbon fiber to flexible graphite was 1:20, and the volume resistivity achieved 4.76 × 10−5 Ω·m when the mass ratio of carbon fiber to flexible graphite was 1:30. With the increase in molding pressure, tensile strength and electrical conductivity had a slight increase. When the flexible conductive composite material was coupled with galvanized steel, sulfate could accelerate the galvanic cell corrosion between the flexible graphite grounding material and galvanized steel. The increase in the sulfate concentration led to more corrosion acceleration. With the increase in corrosion time, the corrosion potential of the flexible graphite grounding material and galvanized steel coupling body decreased to its lowest at 30 days, and then increased gradually. The corrosion current was the highest at 30 days, and then decreased gradually.

Flexible Fiber Shaped Self-Powered System Based on Conductive PANI for Signal Sensing and Energy Harvesting.

As science and technology advance, people are increasingly inclined to use sustainable and portable wearable electronic devices. The traditional supporting power source, batteries, suffers from issues of flexibility and lifespan, severely constraining the development of wearable devices. Alternatively, the self-powered system, serving as a power source, can effectively collect energy from the surrounding environment, achieving maintenance-free operation and high adaptability, which has attracted widespread research. The coaxial fiber-structured self-powering system proposed in this study is based on a supercapacitor (SC) and a triboelectric nanogenerator (TENG). The carbon fiber (CF) has polyaniline (PANI) and rGO connected to it, and a friction layer of silicone rubber is wrapped around the outside. The conductivity of the fiber was increased by multiple PANI graftings, and a coaxial fiber-type TENG with a 2 mm diameter was created. Following weaving, the TENG displays a high power density of 576 mW m-2 and an open-circuit voltage of 160 V and a short-circuit current of 9 μA. In addition, the flexible fiber-shaped supercapacitor uses NiAl-LDHs@CF as the negative electrode and AC@CF as the positive electrode, showing a specific capacitance of up to 281.4 mF cm-2. Furthermore, the SC and TENG are assembled into a coaxial self-power supply system, which has excellent performance and shows extensive potential applications in the field of wearable device power supply.

Research on the Fabrication and Parameters of a Flexible Fiber Optic Pressure Sensor with High Sensitivity

In recent years, flexible pressure sensors have garnered significant attention. However, the development of large-area, low-cost, and easily fabricated flexible pressure sensors remains challenging. We designed a flexible fiber optic pressure sensor for contact force detection based on the principle of backward Rayleigh scattering using a single-mode optical fiber as the sensing element and polymer PDMS as the encapsulation material. To enhance the sensor’s sensitivity and stability, we optimized its structural design, parameters, and fabrication process and measured the fiber strain using an optical frequency domain reflectometer (OFDR). The results showed that the sensor achieved a high sensitivity of 6.93247 με/kPa with a PDMS concentration ratio of 10:1, a curing time of 2 h, and a substrate thickness of 5 mm. The sensor demonstrated excellent linearity and repeatability in static performance tests and was successfully used to monitor the plantar pressure distribution in real time. This flexible fiber optic pressure sensor can be developed via a simple fabrication process, has a low cost, and has high sensitivity, highlighting its potential applications in smart wearables and medical diagnostics.

Molecular regulation of lignin multi-level structure and conformational evolution for the self-powered fire alarm sensors

Many studies are still limited to focusing on the primary structure of biomass macromolecules, ignoring the impact of the multi-level structure of macromolecules and their conformational evolution on the high-value utilization of biomass. In this paper, a novel and clever strategy is designed and executed to regulate and immobilize the multi-level structure of lignin macromolecules. Lignin with different spatial conformations exhibits differences in physical properties and processability, despite their chemical primary structures being highly similar. In order to clearly and intuitively study the impact of multi-level structures, lignin-based carbon nanofibers (CFs) with high requirements for processing and precursor properties have been selected as the high-value utilization. The introduction of lignin with optimized multi-level structures effectively improves fiber morphology, uniform diameter, and flexibility. The resulting lignin-based CFs exhibit excellent refractoriness, stability, flame sensitivity (response time of only 1 s), and good energy storage properties (specific capacitance up to 226.1F/g). Furthermore, the CFs moist-electric generator has a high power generation efficiency, and the output voltage of a single device reaches 0.649 V and the output current is up to 160 μA. This work may explain a long-standing issue: why do lignin macromolecules with similar primary structures exhibit many differences in physical and processing properties, which is of great significance for promoting the industrial utilization of lignin macromolecules.

Drawing on bionics, a flexible silica fiber paper is designed with high temperature resistance and hydrophobic properties

In this paper, a flexible silica fiber paper (SFP) made of silica ceramic with excellent high-temperature resistance was prepared. After modification with fluorosilane, the contact angle of the modified fiber paper with water was 153°. At the same time, the modified fiber paper maintains the superhydrophobic properties even after high-temperature heat treatment (150 ± 1° after treatment at 400 °C) and shows excellent hydrophobic performance at high temperatures. The produced ceramic inorganic fiber paper has good comprehensive properties and is a promising skin material for aircraft.

Evaluation of Fracture Resistance of Reattached Tooth Fragments Restored Using Fiber-reinforced Composites: A Systematic Review.

This systematic review examined the current literature to evaluate the fracture resistance of the tooth fragments reattached using fiber-reinforced composites (FRC). An electronic search was performed on Scopus, PubMed, and Web of Science databases according to specific inclusion and exclusion criteria to identify relevant articles to be included until January 2023. Articles with full text available in the English language for randomized control studies, observational studies, retrospective studies, and in vitro studies conducted on permanent human teeth were selected. The risk of bias was assessed in all studies using the OHAT tool. Out of 16 search results, seven in vitro studies with a total of 415 samples were included in the review. Three studies reported that reinforcement using rigid FRC posts improves fracture resistance of reattached anterior teeth, three studies reported that reinforcement using flexible fiber bundles enhances the fracture strength of reattached posterior teeth and one study reported that the use of flexible polyethylene fibers improves fracture resistance in molars with reattached cusps. Within the limitations of the studies included in the review, there is low-quality evidence that reinforcement of reattached fragments using FRC posts or fibers improves fracture resistance. The reattached fractured fragments may be susceptible to re-fracture. The use of FRC to reinforce the resin composite used for reattachment may enhance the bond strength and increase resistance to fracture. How to cite this article: Albar NHM. Evaluation of Fracture Resistance of Reattached Tooth Fragments Restored Using Fiber-reinforced Composites: A Systematic Review. J Contemp Dent Pract 2024;25(6):605-615.

Pressure Visualization and Quantification Photonic Skin Based on Flexible Optical Fiber Combiner

AbstractThe integration of pressure quantification and visualization enhances pressure perception, accuracy, and efficiency. Current solutions require improvements in quantization accuracy, structural simplicity, and integration. We proposed a novel photonic skin comprising a 3 × 1 flexible optical fiber combiner, integrating red, green, and blue light emitting diode (LED) chips through three flexible optical fibers. Under pressure, changes in the optical fibers' transmission loss alter the output light intensity ratio, thus inducing a color shift at the combiner's output. This visible change can be precisely quantified using a color sensor chip. Performance metrics include sensing range up to 33N, sensitivity between 0.04 and 0.24 dB N−1, detection limit below 0.08 N, response time of 500 ms, recovery time of 400 ms, and durability exceeding 2000 cycles. A compact flexible circuit board manages light source driving, data acquisition, and wireless communication, forming a wearable photonic skin system. This system enables visual recognition and quantitative measurement of pressure across diverse scenarios, including different tactile modes, multi‐position pressure, finger bending, and neck movement. For oral occlusion force detection, the spatial separation of the sensing and visualization areas enables the system to simultaneously provide accurate measurements and intuitive visual assessment.

Flexible multimaterial fibers in modern biomedical applications.

Biomedical devices are indispensable in modern healthcare, significantly enhancing patients' quality of life. Recently, there has been a drastic increase in innovations for the fabrication of biomedical devices. Amongst these fabrication methods, the thermal drawing process has emerged as a versatile and scalable process for the development of advanced biomedical devices. By thermally drawing a macroscopic preform, which is meticulously designed and integrated with functional materials, hundreds of meters of multifunctional fibers are produced. These scalable flexible multifunctional fibers are embedded with functionalities such as electrochemical sensing, drug delivery, light delivery, temperature sensing, chemical sensing, pressure sensing, etc. In this review, we summarize the fabrication method of thermally drawn multifunctional fibers and highlight recent developments in thermally drawn fibers for modern biomedical application, including neural interfacing, chemical sensing, tissue engineering, cancer treatment, soft robotics and smart wearables. Finally, we discuss the existing challenges and future directions of this rapidly growing field.

Dynamics for rigid–flexible coupled solar panel multibody system composed of composite laminated plates

Composite laminates are widely employed in the fabrication of solar panels in modern spacecraft engineering because of their superior durability, mechanical qualities, and cost-effectiveness. This research is dedicated to multibody system dynamics modeling of composite laminate solar panels, specifically the coupling system between the rigid main body and the flexible solar panels. In this study, the rigid body is modeled using the natural coordinate formulation (NCF), and for the flexible solar panel, the absolute nodal coordinate formulation (ANCF) with a 36-DOF reduced-order composite thin shell element is used to accurately capture the coupling effect of the solar panel under large motion and deformation. Compared to a 48-DOF fully parameterized thick plate element, this method efficiently avoids shear locking and improves numerical solution convergence efficiency. Based on the Kirchhoff theory and the constitutive relationship of composite laminates, a dynamic model of the multibody system is developed, taking into account the rigid-flexible coupling effect and the kinematic constraints. This work thoroughly discusses the dynamic behavior of solar panel deployment using a comparative analysis of numerical simulation and virtual prototype simulation, and the accuracy is verified. The findings indicate that the flexible characteristics and fiber orientation of composite laminates have a significant impact on the dynamic response of solar panels during deployment. Furthermore, the bang-bang attitude controller is designed, and the difference in dynamic response between the two modeling methods in controlled and uncontrolled states is studied, providing an important theoretical foundation and technical support for solar panel design and analysis.

Nanofiber Space-Confined Fabrication of High-Performance Perovskite Films for Flexible Conversion of Fluorescence Quantum Yields in LED Applications.

Perovskite is an advanced optoelectronic semiconductor material that has garnered significant attention in recent years. However, its drawback lies in its environmental instability, limiting its practical applications. To tackle this issue, this research delved into the idea of creating a space-confined structure and used electrospinning to produce a film of perovskite nanocomposite fibers. By effectively encapsulating perovskite nanocrystals into a polymer matrix, the perovskite could be shielded from water and oxygen in the environment, thereby reducing the likelihood of perovskite decomposition and enhancing the stability of its structure and properties. This study examined the influence of material composition and the spinning process on the nanofiber structure to create good spatial confinement. This strategy resulted in a high photoluminescence quantum yield of over 80% and a long-term environmental stability of as long as 1000 h over 90% of the original PLQY. By harnessing the flexibility of the composite fibers, this study demonstrated the potential applications and performance of this nanocomposite film in flexible quantum fluorescence conversion for LED applications.

Intrinsically Flexible Phase Change Fibers for Intelligent Thermal Regulation

AbstractOwing to the significant latent heat generated at constant temperatures, phase change fibers (PCFs) have recently received much attention in the field of wearable thermal management. However, the phase change materials involved in the existing PCFs still experience a solid–liquid transition process, severely restricting their practicality as wearable thermal management materials. Herein, we, for the first time, developed intrinsically flexible PCFs (polyethylene glycol/4,4′‐methylenebis(cyclohexyl isocyanate) fibers, PMFs) through polycondensation and wet‐spinning process, exhibiting an inherent solid‐solid phase transition property, adjustable phase transition behaviors, and outstanding knittability. The PMFs also present superior mechanical strength (28 MPa), washability (>100 cycles), thermal cycling stability (>2000 cycles), facile dyeability, and heat‐induced recoverability, all of which are highly significant for practical wearable applications. Additionally, the PMFs can be easily recycled by directly dissolving them in solvents for reprocessing, revealing promising applications as sustainable materials for thermal management. Most importantly, the applicability of the PMFs was demonstrated by knitting them into permeable fabrics, which exhibit considerably improved thermal management performance compared with the cotton fabric. The PMFs offer great potential for intelligent thermal regulation in smart textiles and wearable electronics.

A Decade of Insights: Reevaluating the Use of the Flexible-Fiber CO2 Laser in Brain Tumor Surgery-Efficacy, Challenges, and Lessons Learned.

The introduction of flexible fiber technology in the early 2000s revitalized the interest in the CO2 laser for neurosurgical applications, making it suitable for microsurgical procedures. Despite its widespread use, specific indications for the CO2 laser in neurosurgery remains undefined. This study evaluates the efficacy and limitations of the CO2 laser in brain tumor surgery. This retrospective observational single-center study analyzed the use of the CO2 laser in intracranial neoplasm surgeries from 2011 to 2021. A total of 94 patients were assessed, focusing on demographics, tumor characteristics, surgical duration, complications, and laser-specific issues. We used a five-tiered scoring system to assess laser effectiveness in both debulking and dissection tasks; with resection extent assessed following established guidelines. The CO2 laser was highly effective in debulking solid tumors, achieving a 76.5% gross total resection rate, while being less effective in softer, highly vascularized tumors. The average effectiveness scores for dissection (2.6±0.8) were significantly lower than for debulking (3.2±1.2). Two major complications were directly associated with laser use. Effectiveness improved over time, particularly in the latter half of the study, and varied across tumor types, with notable utility in meningiomas and vestibular schwannomas but lower scores in glial tumors. The CO2 laser is a valuable tool in neurosurgery, especially for solid tumors in specific anatomical locations. Careful patient selection is crucial, and the laser complements rather than replaces conventional surgical tools. Ongoing technological advancements suggest broader future applications in neurosurgery.

Intrinsically Flexible Phase Change Fibers for Intelligent Thermal Regulation.

Owing to the significant latent heat generated at constant temperatures, phase change fibers (PCFs) have recently received much attention in the field of wearable thermal management. However, the phase change materials involved in the existing PCFs still experience a solid-liquid transition process, severely restricting their practicality as wearable thermal management materials. Herein, we, for the first time, developed intrinsically flexible PCFs (polyethylene glycol/4,4'-methylenebis(cyclohexyl isocyanate) fibers, PMFs) through polycondensation and wet-spinning process, exhibiting an inherent solid-solid phase transition property, adjustable phase transition behaviors, and outstanding knittability. The PMFs also present superior mechanical strength (28 MPa), washability (>100 cycles), thermal cycling stability (>2000 cycles), facile dyeability, and heat-induced recoverability, all of which are highly significant for practical wearable applications. Additionally, the PMFs can be easily recycled by directly dissolving them in solvents for reprocessing, revealing promising applications as sustainable materials for thermal management. Most importantly, the applicability of the PMFs was demonstrated by knitting them into permeable fabrics, which exhibit considerably improved thermal management performance compared with the cotton fabric. The PMFs offer great potential for intelligent thermal regulation in smart textiles and wearable electronics.

Determination of Kinetic Parameters and Thermal Characteristics of Epoxy Casuarina Bio Composites

By reinforcing casuarina equisetifolia leaf, a flexible bio fibre, in different volume proportions of 4%, 8%, 12%, 16%, and 20% into the epoxy resin, a bio-based composite was produced utilizing the hand layup method. FT IR spectrum was used to verify the production of epoxy casuarina composite. The produced composites have undergone an extensive thermal investigation using Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), Derivative Thermogravimetric (DTG) study and Differential Scanning Calorimetry (DSC) analysis. It has been observed that increasing the percentage of casuarina fibre content enhances the thermal stability of epoxy resin. Horowitz- Metzger (HM), Broido and Coats-Redfern (CR) models were worked and the result revealed that the decomposition of casuarina epoxy composite followed one Dimensional Diffusion Model with coefficient of correlation value close to 1. The thermodynamic parameters including Activation energy (Ea), frequency factor (A), Gibbs free energy (ΔG), entropy (ΔS) and enthalpy (ΔH) of epoxy casuarina composites were found to increase with increase in fibre contents. This makes the composite more suitable for making high performance engineering material for various applications.

Series solution and its extension for the nonlinear flow response of soft hair beds

In nature and engineering applications, flexible fiber beds covering biological surfaces can play a role in reducing resistance. These fibers deform under the action of fluids, and this deformation affects the fluid flow state, forming a complex fluid–solid interaction phenomenon. To quantitatively analyze these issues, the physical model is simplified. We focus on the deformation of a soft hair bed caused by Stokes flow. Additionally, we study the deformation of a single hair under Stokes flow in greater detail. The deformation problem of an elastic single fiber in a channel caused by Stokes flow can be described by a nonlinear integral equation. We have obtained a new series solution, which has been compared with the previous perturbation method to verify the accuracy and effectiveness of the series solution. Meanwhile, we have further provided an extended form of flexible fiber deformation through experimental fitting. This fluid–solid interaction problem involves multiple fields and is very important in many natural and engineering systems. The research in this paper can not only help us better understand complex phenomena in nature but also delve into the interaction mechanism between fluids and solids, providing a theoretical basis for future scientific research and engineering applications.

Flexible and wearable multilayer structure fiber sensor for motion and human physiological signal monitoring

AbstractThe development of flexible piezoresistive sensors has increasingly attracted widespread attention due to their various potential applications in wearable devices, human–machine interfaces, and health monitoring systems. Developing high‐performance sensors that can accurately monitor movement and human health monitoring is very necessary. This study uses silver nanoparticles, MXene, and polypyrrole to prepare conductive fabrics based on various fabrics through layer‐by‐layer encapsulation. Finally, conductive fabrics with different layers were encapsulated to prepare a multilayer fiber sensor. Next, the series piezoresistive performance of sensors made of different fabric materials and sensors with different layers were tested. The experimental results show that the sensor prepared has the best performance when the selected fabric material is mulberry silk and the number of layers of the fabric is five. After testing, the sensitivity of the sensor is 4.9029 at low strain and 0.7901 at high strain. Moreover, it exhibits good stability during 1600 compression‐release cycles and temperatures range from −20 to 60°C. The designed sensor performs well in motion and human physiological signal monitoring. This study provides new ideas and references for the design and research of multilayer fiber sensors.