Flexible Fiber Research Articles

Achieving superior high-life-stability and stable structure for flexible fiber electrodes inspired by Bamboo rice dumpling

MnO2 is widely recognized as promising pseudocapacitive materials to address the issue of low energy density in fiber supercapacitors. However, it severely suffers from poor cycling stability caused by structure damages. Inspired by Chinese bamboo rice dumplings, herein we demonstrate the strategy of building conductive polymer Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires around the MnO2 nanoparticles to address the issue. Benefiting from the tight winding of PEDOT nanowires, the flexible fiber electrode achieves a stable structure and an extraordinary cycle stability. Density functional theory calculations further reveals that the charge redistribution of MnO2/PEDOT interface and Fe3+ doping during polymerization in PEDOT improve the conductivity, facilitate ion adsorption, inhibit the hydrogen evolution reaction, and expand the voltage window. Accordingly, the fiber-shaped supercapacitor based on this electrode exhibits a high cycle lifespan of 86% after 22,000 cycles with capacitance (23.5 F cm−3), energy density (8.32 mWh cm−3), power density (8000 mW cm−3) and voltage window of 1.6 V. Furthermore, it can withstand various angles of bending without losing capacity. Our study provides a pathway to construct MnO2 with a stable structure and cycling life, and could be further used for developing other materials with unstable structure in flexible electronic devices.

Investigating the tensile and flexural strength of sunflower oil treated Ethiopian Highland bamboo fibre reinforced polyester composites

As bamboo composites have wide applications, this study investigated the mechanical properties (tensile and flexural) of oil-treated Ethiopian Highland bamboo fibre/polyester laminated composites using an experimental and analytical approach. The goal of oil treatment is to soften the components of bamboo fibre, resulting in more flexible fibre strands with high tensile and flexural strengths. The composite was manufactured using hand layup methods with a fibre/matrix ratio of 35%/ 65% by volume. The fibre orientations used in the laminates were [0]5 for both tensile and bending tests. The maximum tensile and flexural stresses of oil-treated bamboo fibre-reinforced polyester composite (OBFP) were 193.3 MPa and 173.4 MPa, respectively. These outcomes surpassed untreated bamboo fibre-reinforced polyester composites by 39.6% and 50.2% (UBFP), respectively. The fibre tensile and flexural strains were increased by 25.1% and 25.7%, respectively, as a result of oil treatment. According to the findings, oil-treated bamboo fibre laminates exhibited better tensile and flexural characteristics. The oil treatment lubricated the fibre and increased strand flexibility to reduce abrupt breakage.

2D carbon network arranged into high-order 3D nanotube arrays on a flexible microelectrode: integration into electrochemical microbiosensor devices for cancer detection

In this work, we develop a new type of mesoporous 2D N, B, and P codoped carbon network (NBP-CNW) arranged into high-order 3D nanotube arrays (NTAs), which are wrapped onto a flexible carbon fiber microelectrode, and this microelectrode is employed as a high-performance carbon-based nanocatalyst for electrochemical biosensing. The NBP-CNW-NTAs synthesized by a facile, controllable, ecofriendly and sustainable template strategy using ionic liquids as precursors possess a high structural stability, large surface area, abundant active sites, and effective charge transport pathways, which dramatically improve their electrocatalytic activity and durability in the redox reaction of cancer biomarker H2O2. Benefiting from these unique structural merits, superb electrochemical activity and good biocompatibility, the NBP-CNW-NTAs-modified microelectrode demonstrates excellent sensing performance toward H2O2 and is embedded in a homemade microfluidic electrochemical biosensor chip for the real-time tracking of H2O2 secreted from different live cancer cells with or without radiotherapy treatment, which provides a new strategy for distinguishing the types of cancer cells and evaluating the radiotherapeutic efficacy of cancer cells. Furthermore, the functional microelectrode is integrated into an implantable probe for the in situ detection of surgically resected human specimens to distinguish cancer tissues from normal tissues. These will be of vital significance for cancer diagnoses and therapy in clinical practice.

Copper-Coordinated Cellulose Fibers for Electric Devices with Motion Sensitivity and Flame Retardance.

Nanocomposite conductive fibers are of great significance in applications of wearable devices, smart textiles, and flexible electronics. Integration of conductive nanomaterials into flexible bio-based fibers with multifunctionality remains challenging due to interface failure, poor flexibility, and inflammability. Although having broader applications in textiles, regenerated cellulose fibers (RCFs) cannot meet the requirements of wearable electronics owing to their intrinsic insulation. In this study, we constructed conductive RCFs fabricated by coordinating copper ions with cellulose and reducing them into stable Cu nanoparticles coated on their surface. The Cu sheath offered excellent electrical conductivity (4.6 × 105 S m-1), electromagnetic interference shielding, and enhanced flame retardance. Inspired by plant tendrils, the conductive RCF was wrapped around an elastic rod to develop wearable sensors for human health and motion monitoring. The resultant fibers not only form stable conductive nanocomposites on the fiber surface by chemical bonds but also exhibit a huge potential for wearable devices, smart sensors, and flame-retardant circuits.

In situ growth of CsPbBr3@PS flexible fiber papers by one step electrospinning with high stability toward fluorescent sensor

Recently, all-inorganic CsPbX3 (Br, I, CI) perovskites are hot and potential materials which apply to photoelectric device, due to their excellent photoelectric properties such as high carrier mobility, high fluorescence, etc. However, the poor stability greatly restricts their practical applications. In this paper, CsPbBr3 nanocrystals (NCs) were in-situ encapsulated into PS polymer nanofibers by one step electrospinning with highly uniform size and spatial distribution. The hydrothermal stability of the obtained CsPbBr3@PS flexible fiber paper was radically improved with a photoluminescence quantum yield (PLQY) of 66.3%. The PL strength remained 97.2% of the initial value after immersion in water for 10 days. Their PLQY remains above 50% of its original value after heating at 80 °C for 5 h. Due to the excellent optical properties and stability of CsPbBr3@PS flexible fiber papers, the detection for rhodamine 6G (R6G) and rhodamine B (RhB) aqueous solution with high FRET value of 24.7% and 21.4%, respectively. Moreover, the minimum detection limit for R6G aqueous solution is 0.005 ppm. This study suggests that the CsPbBr3@PS flexible fiber paper is a good candidate for fabricating flexible optoelectronic devices, promising application potentials in lighting and display fields.

An energy-saving composite textile for thermal management

To reduce energy consumption, personal thermal management device has attracted great attention. Developing flexible fibers with low thermal conductivity or low emissivity is crucial but is still a great challenge. In this work, we developed a flexible and versatile composite textile with excellent passive and active heating capabilities. Via designing of the pore morphology and solid phase network, the aerogel textile of TPU/SiO2 (named as T-textile) is obtained with a low thermal conductivity of 0.037 W/mK. The T-textile also exhibits high flexibility with a fracture strain of 580%, while the low ductility is usually an issue for aerogel textures. Meantime, the conductive textile of TPU/Ag (S-textile) is fabricated with a low infrared emissivity of 0.40 and a high electric conductivity of 248.99 S/mm. The S-textile also possesses excellent electromagnetic shielding capability (above 75 dB). The simulated skin (∼27.4 °C) covered with layers of ST (S + T) and STT (S + T + T) textiles could be warmed to 32.6 °C and 35 °C, respectively. Also, with only 0.6 V, the simulated skin covered with S-textile could be heated to 50 °C, while with the TS textile (the ST textile flipped), it is 58 °C. The composite textile offers a combined solution for thermal insulation, Joule heating, flexibility, breathability and electromagnetic shielding capability, making it a smart personal thermal management device for complex scenarios.

Design and optimization of medium-high frequency FBG acceleration sensor based on symmetry flexible hinge structure

A flexible hinge fiber Bragg grating (FBG) acceleration sensor based on the symmetry mass block is proposed to address poor transverse performance and lower sensitivity in medium- and high-frequency. The dual mass block design causes the FBG fiber to vibrate while simultaneously being stretched or compressed in the reverse direction. Thus, the FBG's sensitivity is greatly improved, and its deformation is double that of the single hinge construction. MATLAB software theoretically investigates and optimizes the sensor's natural frequency and sensitivity. In contrast, ANSYS analyzes static structural stress and simulation. The implementation of the sensors is assessed through an experimental test. The accelerometer's natural frequency is 1550 Hz, and its working stability frequency range is flat at 400–1000 Hz. The amplitude anti-interference of the sensor is approximately 3.27%, and the average sensitivity's linearity is roughly 66 pm/g. Developing medium and high-frequency vibration data is essential for the health monitoring and evaluation of constructions such as bridges, railroads, and tunnels.

Amphibian‐like Flexible Organic Crystal Optical Fibers for Underwater/Air Micro‐Precision Lighting and Sensing

AbstractVisible light guiding optical fibers with underwater operational capability are highly desired for subaquatic communication and sensing technologies. Herein, we present mechanically flexible, blue‐violet fluorescent (4,4′‐bis(2,6‐di(1H‐pyrazol‐1‐yl)pyridin‐4‐yl)biphenyl) (BPP) crystal waveguides with high‐aspect ratio. These milli‐meter‐long BPP crystals guide light actively and passively in ambient and underwater conditions demonstrating their amphibian‐like character. Due to the crystal's high flexibility, the optical fiber's output light direction in submerged and ambient states can be altered mechanically for high‐precision lighting and sensing applications. The development of such multi‐environment‐compatible and mechanically flexible organic optical fibers acting as sensing materials possess enormous potential for short‐range underwater photonic technologies.

Amphibian-like Flexible Organic Crystal Optical Fibers for Underwater/Air Micro-Precision Lighting and Sensing.

Visible light guiding optical fibers with underwater operational capability are highly desired for subaquatic communication and sensing technologies. Herein, we present mechanically flexible, blue-violet fluorescent (4,4'-bis(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)biphenyl) (BPP) crystal waveguides with high-aspect ratio. These milli-meter-long BPP crystals guide light actively and passively in ambient and underwater conditions demonstrating their amphibian-like character. Due to the crystal's high flexibility, the optical fiber's output light direction in submerged and ambient states can be altered mechanically for high-precision lighting and sensing applications. The development of such multi-environment-compatible and mechanically flexible organic optical fibers acting as sensing materials possess enormous potential for short-range underwater photonic technologies.

Flexible carbon fiber cloth supports decorated with cerium metal- organic frameworks and multi-walled carbon nanotubes for simultaneous on-site detection of Cd2+ and Pb2+ in food and water samples

The widespread heavy metal pollution endangers human health; hence, accurate on-site detection and quantification of heavy metal content in the surroundings is a vital step in reversing the harmful effect. Herein, an electrochemical sensor based on flexible cerium metal–organic framework@multi-walled carbon nanotubes/carbon cloth (CeMOF@MWCNTs/CC) was constructed for simultaneous on-site detection of Cd2+ and Pb2+ in food and water samples. The rich carboxyl groups of MWCNTs provided abundant sites for the adsorption of Cd2+ and Pb2+, and the mutual conversion of Ce3+ and Ce4+ in CeMOF facilitated the reduction and reoxidation of metal ions. The prepared electrode showed excellent performance in the simultaneous measurement of Cd2+ and Pb2+, with detection limits of 2.2 ppb and 0.64 ppb, respectively. More importantly, the sensing platform has been successfully used to detect simultaneously Cd2+ and Pb2+ in grain and water samples, and the detection results were consistent with the standard methods, showing great potential in environmental monitoring and food safety.

Reduced graphene oxide influences morphology and thermal properties of silk/cellulose biocomposites

In recent decades, research into biomaterials such as silk or cellulose has rapidly expanded due to their abundance, low cost, and tunable morphological as well as physicochemical properties. Cellulose is appealing due to its crystalline and amorphous polymorphs while silk is attractive due to its tunable secondary structure formations which is made up of flexible protein fibers. When these two biomacromolecules are mixed, their properties can be modified by changing their material composition and fabrication methodology, e.g., solvent type, coagulation agent, and temperature. Reduced graphene oxide (rGO) can be used to increase molecular interactions and stabilization of natural polymers. In this study, we sought to determine how small amounts of rGO affect the carbohydrate crystallinity and protein secondary structure formation as well as physicochemical properties and how they affect overall ionic conductivity of cellulose-silk composites. Properties of fabricated silk and cellulose composites with and without rGO were investigated using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, X-Ray Scattering, Differential Scanning Calorimetry, Dielectric Relaxation Spectroscopy, and Thermogravimetric Analysis. Our results show that addition of rGO influenced morphological and thermal properties of cellulose-silk biocomposites, specifically through cellulose crystallinity and silk β-sheet content which further impacted ionic conductivity.

Controlling extrudate volume fraction through poroelastic extrusion of entangled looped fibers

When a suspension of spherical or near-spherical particles passes through a constriction the particle volume fraction either remains the same or decreases. In contrast to these particulate suspensions, here we observe that an entangled fiber suspension increases its volume fraction up to 14-fold after passing through a constriction. We attribute this response to the entanglements among the fibers that allows the network to move faster than the liquid. By changing the fiber geometry, we find that the entanglements originate from interlocking shapes or high fiber flexibility. A quantitative poroelastic model is used to explain the increase in velocity and extrudate volume fraction. These results provide a new strategy to use fiber volume fraction, flexibility, and shape to tune soft material properties, e.g., suspension concentration and porosity, during delivery, as occurs in healthcare, three-dimensional printing, and material repair.

High‐Energy‐Density Graphene Hybrid Flexible Fiber Supercapacitors

AbstractGraphene fiber‐based supercapacitors (GFSCs) as flexible energy‐storage devices have achieved much in the wearable electronics. However, the GFSCs still suffer insufficient energy density, and of which desirable balance between mechanical and electrochemical properties has not been realized. Herein, we developed AgI and conductive polymer assisted co‐enhancement strategy to prepare the high‐performance GFSCs with super‐high energy density, favorable mechanical properties, and superior electrochemical properties. The conductive binder polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT) was introduced into the GO spinning solution to enhance RGO fiber strength, conductivity, and electrochemical performance by forming a strong interface with GO in the spinning solution. On the other hand, the synergistic effect of micro‐ and nano‐scale AgI grown on the fiber surface and aqueous gel electrolyte widen the potential window of the GFSC to 1.6 V, which is much higher than that of reported GFSCs, and resulting in a significantly increased energy density. At 0.1 A cm−3, the volumetric capacitance and energy density of the fabricated GFSCs are as high as 166.6 F cm−3 and 29.65 mWh cm−3, respectively. The high strength and flexibility of the hybrid fibers endowed the GFSCs with ∼100 % capacitance retention when bent to 180°. This work opens a new way to design and fabricate high‐performance GFSCs.

Data Glove Based on Flexible Fiber Optic Sensor for Gesture Capture

The development of data glove is very rapid, and it is widely used in the field of human-robot interaction. Flexible optical fiber sensors are widely used in data gloves. Hereby, a flexible data glove based on space-division multiplexed flexible optical fiber sensor is proposed. The fiber exhibits high optical transmission stability and good sensing performance under deformation. Our data glove accurately recognizes and tracks gestures, and then guide the manipulator to make the same gesture. It is believed that the application of data glove will be more widespread.

Flexible Carbon Fiber/TiO2 Nanopillars Electrode in the Detection of Glucose Under Photoexcitation

The development and utilization of biosensors have received a great attention from the scientific community due to their wide applications in the areas of food safety, medical diagnosis, environmental monitoring and other fields. In this paper, we report the development of a novel photoelectrochemical (PEC) sensor for glucose detection using a flexible carbon fiber/TiO2 nanopillars electrode. The carbon fiber/TiO2 nanopillars was prepared by two step process in which the first step is to grow TiO2 seeds over carbon fiber by magnetron sputtering while the second step leads the growth of TiO2 nanopillars over flexible carbon fibers substrate. Under photoexcitation, the PEC sensor showed a significant enhancement in the sensitivity for glucose detection. The detection mechanism was based on the photoelectrochemical oxidation of glucose to gluconic acid, which generated an electrical signal that was proportional to the glucose concentration. The electrochemical examinations were performed at low glucose concentrations in the range of 1–5 mM (mmol L−1) to investigate the corresponding photocurrent. The results showed that the photocurrent increases with increasing the glucose concentration. This is of great significance for the detection of hypoglycemia, and has good application prospects in the fields of nano-detection, biological diagnosis and wearable devices. The flexible carbon fiber/TiO2 PEC sensor developed in this study is a promising approach for the development of wearable devices for continuous glucose monitoring.

In-situ interface reinforcement for 3D printed fiber electrodes

The growing demand for wearable electronics has boosted research on flexible fiber batteries. 3D printing has been applied to fiber battery manufacturing, in which tremendous amount of polymer binders with low conductivity are required. Replacing polymer by conducting skeleton such as graphene can offer long-range conductivity and high active material ratio. However, poor interaction and vast voids between active materials and skeletons result in fragile structure with inferior stabilities. Herein, a facile in-situ interface reinforcement method is proposed to print stable binder-free fiber electrodes. Electrode inks consisting of common LiFePO4 (LFP) particles and graphene oxide (GO) are directly printed in a solution containing dopamine and calcium ions. Catalyzed by Ca2+, dopamine that permeated into the fiber could rapidly polymerize and synchronously establish crosslinks during printing. Subsequently, polydopamine-derived carbon (PDC) networks efficiently reinforce the interface. The PDC at interfaces enriches the electron-transfer pathways and ensures a tight connection through covalent and π-π bonding. The reinforcement enables the printed binder-free electrodes to possess remarkably higher stability, flexibility, and durability under deformation. Additionally, the proposed method has remarkable application potential both for individual fiber batteries and directly printed battery textiles, thereby enabling new possibilities for future wearable energy-storage fabrics.

Flexible fiber cholangioscope for detection of near-infrared fluorescence

Video 1Flexible fiber cholangioscope for detection of near-infrared fluorescence.

Structural Optimization of Long and Flexible Composite Cover with Topography Method and Examination of Frequency Values

In this study, the finite element model of the long, thin, and flexible carbon fiber reinforced composite cover design prepared using the Unigraphics NX program CAD module was analyzed in ANSYS program. Topography optimization was performed by transferring the analysis results to the GENESIS program. The cover rib created after optimization was combined with the initial design, and necessary corrections were made in the design based on the topography guide. The rib design, created by conventional methods, weigh the same as the optimum design, is combined with of the initial design. Modal analysis of initial, conventional rib and optimum rib design was performed in ANSYS environment. When the findings were evaluated it was observed that the composite cover, which was remodeled after topography optimization, increased by 33.3% compared to the initial design, while its natural frequency (mode 2) increased approximately 1.6 times. In addition, the lowest moment of inertia value has been obtained in the cover design with optimum design geometry. Then, the conventional design, which has the same mass as the new design, was compared and it was revealed by the data that the new design was more resistant. According to the results obtained, the most suitable rib geometry to be preferred for this and similar types of long and flexible structures to have a more resistant structure has been determined.

Stochastic model for predicting the shape of flexible fibers in suspensions

The shape of flexible fibers in a suspension varies depending on the hydrodynamic interaction of each fiber with the flow and with the neighboring fibers. By examining the total fiber forces from direct numerical simulations, this study proposes a reduced-order stochastic model that predicts the three-dimensional shape of fibers settling inertially in a suspension of different concentrations. While at low concentrations gravity is the main contributor to the planar deformation of the fibers, at higher concentrations, the interaction of fibers with each other creates large out of plane deformations.

Multichannel Gradient Piezoelectric Transducer Assisted with Deep Learning for Broadband Acoustic Sensing.

As an important part of human-machine interfaces, piezoelectric voice recognition has received extensive attention due to its unique self-powered nature. However, conventional voice recognition devices exhibit a limited response frequency band due to the intrinsic hardness and brittleness of piezoelectric ceramics or the flexibility of piezoelectric fibers. Here, we propose a cochlear-inspired multichannel piezoelectric acoustic sensor (MAS) based on gradient PVDF piezoelectric nanofibers for broadband voice recognition by a programmable electrospinning technique. Compared with the common electrospun PVDF membrane-based acoustic sensor, the developed MAS demonstrates the greatly 300%-broadened frequency band and the substantially 334.6%-enhanced piezoelectric output. More importantly, this MAS can serve as a high-fidelity auditory platform for music recording and human voice recognition, in which the classification accuracy rate can reach up to 100% in coordination with deep learning. The programmable bionic gradient piezoelectric nanofiber may provide a universal strategy for the development of intelligent bioelectronics.