Conductive Fibers Research Articles

High Thermal Conductive Liquid Crystal Elastomer Nanofibers.

Liquid crystal elastomers (LCEs), consisting of polymer networks and liquid crystal mesogens, show a reversible phase change under thermal stimuli. However, the kinetic performance is limited by the inherently low thermal conductivity of the polymers. Transforming amorphous bulk into a fiber enhances thermal conductivity through the alignment of polymer chains. Challenges are present due to their rigid networks, while cross-links are crucial for deformation. Here, we employ hydrodynamic alignment to orient the LCE domains assisted by controlled in situ cross-linking and to remarkably reduce the diameter to submicrons. We report that the intrinsic thermal conductivity of LCE fibers at room temperature reaches 1.44 ± 0.32 W/m-K with the sub-100 nm diameter close to the upper limit determined in the quasi-1D regime. Combining the outstanding thermal conductivity and thin diameters, we anticipate these fibers to exhibit a rapid response and high force output in thermomechanical systems. The fabrication method is expected to apply to other cross-linked polymers.

Electromagnetic interference shielding performance and piezoresistivity of multifunctional cement composites by adopting conductive aggregates

This study explores the application of multifunctional cement composites prepared with graphene-coated conductive aggregate (Gr@Ag) and carbon fiber (CF). The electromagnetic interference (EMI) shielding effectiveness, electrical conductivity, and piezoresistive performance of cement mortars were investigated by varying the aggregate to binder (a/b) ratio and CF content. It was found that the EMI shielding effectiveness of cement mortar was enhanced by 24.8 % with the a/b ratio increased from 1.0 to 2.5, reaching 20.07 dB with a 3 mm thickness specimen. This is accompanied by significant improvements in the electrical conductivity and piezoresistive performance of cement mortars. In addition, CFs were included in cement mortars to further improve the electrical performance. Results indicate that there exists a percolation threshold, beyond which extra CF additions did not lead to further increases in the conductivity of cement mortars. The present research has illustrated the novel approach of incorporating the EMI shielding functionality into cement composites by adopting conductive aggregates, expanding the functional and smart performances towards future applications.

3D cellulose network confining MXene/MnO2 enables flexible wet spinning microfibers for high-performance fiber-shaped Zn-ion capacitors

Fiber-shaped Zn-ion capacitors (FSZICs) have shown great potential in wearable electronics due to their long cycle life, high energy density, and good flexibility. Nevertheless, it is still a critical challenge to develop a conductive fiber with long size and high mechanical properties as the FSZIC cathode using sustainable and low-cost materials. Herein, regenerated cellulose (RC) -based conductive microfibers are prepared by a simple, continuous, and scalable wet spinning process. The 3D nanoporous networks of RC caused by physical self-cross-linking allow MXene and MnO2 to be uniformly and firmly embedded. The rapid extrusion and limited drying result in the highly aligned structure of the fibers, endowing the hybrid fiber with an ultra-high tensile strength (145.83 Mpa) and Young's modulus (1672.11 Mpa). MXene/MnO2-RC-based FSZIC demonstrates a high specific capacitance of 110.01 mF cm−3, an energy density of 22.0 mWh cm−3 at 0.57 A cm−3 and excellent cycling stability with 90.5 % capacity retention after 5000 cycles. This work would lead to a great potential of cellulose for application in next-generation green and wearable electronics.

A Straightforward Approach of Wet‐Spinning Poly(3,4‐ethylenedioxythiophene):Polystyrene Sulfate Fibers for Use in All Conducting Polymer‐Based Textile Actuators

Poly(3,4‐ethylenedioxythiophene) (PEDOT), an inherently electrically conductive or conjugated polymer (CP), exhibits the potential to play a significant role in the development of innovative fiber materials for use in smart textiles, such as wearables. Furthermore, these fibers can function as artificial muscles in the emerging field of interactive fiber rubber composites. This study introduces a straightforward and efficient method for creating PEDOT‐based, biomimetic, fiber‐shaped, linearly contracting ionic electroactive polymer actuators. To achieve this, a wet‐spinning technique is presented, which enables a continuous production of PEDOT:polystyrene sulfate (PSS) fibers at high production rates of 34 m h−1, an additional fiber washing step and a sulfuric acid posttreatment step to increase the fibers conductivity. The fibers provide a high conductivity of 1028 S cm−1, maximum tensile strength reaching 182 MPa, and a maximum elongation of 24%. When utilized as CP actuators in an aqueous sodium dodecylbenzenesulfonate electrolyte medium, the fibers demonstrate a repeatable maximum isometric contractile force of 1.64 mN and repeatable linear contractile strain up to 0.56%. Furthermore, a high level of cyclic long‐term actuation stability can be demonstrated. Notably, these contractile strains are, to the best of knowledge, the highest reported values for pristine PEDOT:PSS fibers.

Comparative genomic analysis of nickel homeostasis in cable bacteria

BackgroundCable bacteria are filamentous members of the Desulfobulbaceae family that are capable of performing centimetre‑scale electron transport in marine and freshwater sediments. This long‑distance electron transport is mediated by a network of parallel conductive fibres embedded in the cell envelope. This fibre network efficiently transports electrical currents along the entire length of the centimetre‑long filament. Recent analyses show that these fibres consist of metalloproteins that harbour a novel nickel‑containing cofactor, which indicates that cable bacteria have evolved a unique form of biological electron transport. This nickel‑dependent conduction mechanism suggests that cable bacteria are strongly dependent on nickel as a biosynthetic resource. Here, we performed a comprehensive comparative genomic analysis of the genes linked to nickel homeostasis. We compared the genome‑encoded adaptation to nickel of cable bacteria to related members of the Desulfobulbaceae family and other members of the Desulfobulbales order.ResultsPresently, four closed genomes are available for the monophyletic cable bacteria clade that consists of the genera Candidatus Electrothrix and Candidatus Electronema. To increase the phylogenomic coverage, we additionally generated two closed genomes of cable bacteria: Candidatus Electrothrix gigas strain HY10‑6 and Candidatus Electrothrix antwerpensis strain GW3‑4, which are the first closed genomes of their respective species. Nickel homeostasis genes were identified in a database of 38 cable bacteria genomes (including 6 closed genomes). Gene prevalence was compared to 19 genomes of related strains, residing within the Desulfobulbales order but outside of the cable bacteria clade, revealing several genome‑encoded adaptations to nickel homeostasis in cable bacteria. Phylogenetic analysis indicates that nickel importers, nickel‑binding enzymes and nickel chaperones of cable bacteria are affiliated to organisms outside the Desulfobulbaceae family, with several proteins showing affiliation to organisms outside of the Desulfobacterota phylum. Conspicuously, cable bacteria encode a unique periplasmic nickel export protein RcnA, which possesses a putative cytoplasmic histidine‑rich loop that has been largely expanded compared to RcnA homologs in other organisms.ConclusionCable bacteria genomes show a clear genetic adaptation for nickel utilization when compared to closely related genera. This fully aligns with the nickel‑dependent conduction mechanism that is uniquely found in cable bacteria.

An Experimental Study on Electromagnetic Shielding Effectiveness and Impact Resistance of UHPC for Protective Facilities

The research was conducted on incorporating short carbon fiber and multi-layer graphene into ultra-high performance concrete (UHPC) to improve the dynamic mechanical performance and electromagnetic shielding effectiveness (SE). In the electromagnetic shielding effectiveness testing, the results shown that UHPC with uniformly distributed conductive fibers exhibited superior shielding effectiveness at high frequencies. In comparison to normal concrete, the UHPC demonstrated the capability to withstand higher impact energy. Simultaneously enhancing both electromagnetic shielding characteristics and dynamic mechanical performance of cementitious materials can be challenging. In this study, employing a composite structure was effective solution to overcome this issue. In accordance with the experimental results, a scaled testing protective facility has been constructed, and the research results could provide the reference for the design and construction of protective structures.

Evaluation of piezoresistive response and freeze–thaw damage of self-sensing cement mortar based on conductive fibre

This paper aims to design a self-sensing cement mortar of optimised mechanical and sensing properties considering the water-cement ratio and propose a freeze–thaw damage sensing evaluation parameter. An orthogonal experimental design of compressive strength test and piezoresistive response test was utilised to find the optimal proportion. Freeze–thaw damage sensing test was conducted to found the method for characterising freeze–thaw damage. It is found that the order of the influential factors on stress sensitivity is CF (carbon fibre) content > water-ratio > SF (steel fibre) content. A freeze–thaw damage parameter D k was proposed for characterising freeze–thaw damage based on the slope of the curve of fraction change in resistivity and freeze–thaw cycle numbers and it can be applied to the prediction of the service life of self-sensing cement mortar. The findings of this investigation can help engineers realise freeze–thaw damage evaluation in cement concrete pavement using self-sensing cement mortar.

Assessment of mechanical performance of electrically conductive asphalt pavements using accelerated pavement testing

ABSTRACT Electrically Conductive Asphalt (ECA) pavements are a promising technology for preventing snow and ice accumulation on roadways. This study assesses the mechanical performance of ECA pavements using Accelerated Pavement Testing (APT). Three pavement test strips were constructed in New Jersey: a traditional asphalt layer as test strip-I, an ECA mastic prepared using a combination of asphalt binder and conductive fibres (strip-II), and an ECA-HPTO (high performance thin overlay mixture) layer containing graphite and carbon fibres (strip-III). Each test strip was instrumented with asphalt strain gauges (ASGs), pressure cells, and thermocouples to evaluate the structural responses. A Heavy Vehicle Simulator (HVS) was used to apply 300,000 passes on each test strip using a 40-kN truck tire. The structural integrity of the test strips was evaluated by conducting Heavy Weight Deflectometer (HWD) testing before and after HVS loading. Data from the ASGs revealed that strip III exhibited the highest cracking resistance (nearly 2 times less tensile strain). The rut depths in all test strips were negligible (less than 2 mm). ECA mastic and steel electrodes in the ECA layer impact the structural integrity of test strips, with variations in HWD deflection behaviour indicating the role of electrode spacing in maintaining pavement stability.

Graphene-Perovskite Fibre Photodetectors.

The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non-planar surfaces, and able to maintain performance under mechanical distortions. Here, fibre PDs are prepared by combining rolled graphene layers and photoactive perovskites. Conductive fibres (~500 Ωcm-1) are made by rolling single-layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al2O3 and parylene C), another rolled SLG as a channel, and perovskite as photoactive component. The resulting gate-tunable PD has a response time~9ms, with an external responsivity~22kAW-1 at 488nm for a 1V bias. The external responsivity is two orders of magnitude higher, and the response time one order of magnitude faster, than state-of-the-art wearable fibre-based PDs. Under bending at 4mm radius, up to~80% photocurrent is maintained. Washability tests show~72% of initial photocurrent after 30 cycles, promising for wearableapplications.

Relationship between electrical resistance and single CNT fiber displacement relative to cement matrix – new insights on the electric polarization and spreading at debonded/slipped interface

New relationships between electrical resistance (r) at the CNT fiber-to-cement matrix interface and fiber-to-matrix displacement (u) are established, enhancing the accuracy of self-sensing technology for post-cracking concrete. In the experiment, micromechanical behavior and electrical response (steady and sweeping direct current, DC) were simultaneously monitored through a single-fiber pullout test. It revealed that significant polarization exists at the interface, leading to incorrect resistance measurement. The polarization is eliminated by adding carbon fibers to percolation; after that, an exponential increase of r with u was then observed in both fiber debonding and slippage stages, while r dropped right after full debonding. In the simulation, the spreading of electric current from a partially debonded/slipped interface to distant matrix bulk was computed with a multi-physics FEM model, to correlate resistance change with the interfacial damage level – debonding crack length and fiber slippage. The model-based parametric study showed that the r-u relationship is more sensitive to fiber conductivity than fiber dimensions or matrix conductivity.

Knitting Elastic Conductive Fibers of MXene/Natural Rubber for Multifunctional Wearable Sensors.

Wearable electronic sensors have recently attracted tremendous attention in applications such as personal health monitoring, human movement detection, and sensory skins as they offer a promising alternative to counterparts made from traditional metallic conductors and bulky metallic conductors. However, the real-world use of most wearable sensors is often hindered by their limited stretchability and sensitivity, and ultimately, their difficulty to integrate into textiles. To overcome these limitations, wearable sensors can incorporate flexible conductive fibers as electrically active components. In this study, we adopt a scalable wet-spinning approach to directly produce flexible and conductive fibers from aqueous mixtures of Ti3C2Tx MXene and natural rubber (NR). The electrical conductivity and stretchability of these fibers were tuned by varying their MXene loading, enabling knittability into textiles for wearable sensors. As individual filaments, these MXene/NR fibers exhibit suitable conductivity dependence on strain variations, making them ideal for motivating sensors. Meanwhile, textiles from knitted MXene/NR fibers demonstrate great stability as capacitive touch sensors. Collectively, we believe that these elastic and conductive MXene/NR-based fibers and textiles are promising candidates for wearable sensors and smart textiles.

Micromechanical modeling of thermal conductivities of unidirectional carbon fiber/epoxy composites containing carbon nanotube/graphene hybrids

This article deals with the micromechanical modeling of thermal conductivities of the unidirectional carbon fiber (CF)-reinforced composites with carbon nanotube (CNT)/graphene nanoplatelet (GNP)-enriched epoxy matrix. The thermal conductivity of epoxy-based nanocompounds enriched through the incorporation of CNT/GNP hybrids is estimated within the framework of micromechanics. The significant contribution of several microstructures, including the volume fraction, dimension, and straightness of nanofillers, thermal resistance at the interface of the nanofillers and epoxy matrix, and the percolation effect on the nanocomposite thermal conductivity is considered. Furthermore, the method of cells (MOC) is used to anticipate the axial and transverse thermal conductances of unidirectional composites featuring CFs integrated into the CNT/GNP-enriched polymer nanocomposite matrix. The results reveal that incorporating a combination of GNTs and CNTs into the polymer matrix significantly increases the transverse thermal conduction of the multiphase compound. Several factors contribute to improved thermal conductance of the transverse direction in CF/CNT/GNP composites: (i) higher nanofiller concentration, (ii) presence of straight nanofillers, and (iii) use of larger nanofillers. The predictions of micromechanical modeling give good agreement with available experiments. This study compares the transverse and axial thermal conductivity of unidirectional compounds predicted by MOC method with results obtained using the finite element method.

Scalable development of photocatalysis-mediated aquatic habitat restoration devices based on TiO2/graphene/BiVO4 and the application in black-odorous river treatment

A novel concept of photocatalysis-mediated aquatic habitat restoration materials (PMAHRM) has been introduced in this study. The primary objective of development lies in enhancing the aquatic habitat, indirectly fostering favorable living conditions for aquatic organisms and fostering their growth. TiO2/Graphene/BiVO4 (TGB), serving as a PMAHRM, was constructed through a hydrothermal process. The absorption wavelength extends to 504 nm. Furthermore, a PMAHRM device with a dual-function area structure based on TGB and in-situ microorganisms immobilized separately has been designed. Both sections were seamlessly integrated through the use of conductive fibers. The device demonstrates a RhB removal rate of 85.70 % under visible light. During the nearly six-month field trial for the restoration of a black-odorous river, the scalable developed TGB devices, in conjunction with Myriophyllum verticillatum, were employed to achieve comprehensive restoration outcomes. The results showed significant decreases in NH3-N, TP, and COD concentrations by 85.96 %, 77.78 % and 73.53 %. The transparent index rising 3.3 times. TN, TP, and OM concentrations of sediment decreased by 10.64 %, 9.60 % and 34.08 % respectively. The enhancement of habitat quality led to various positive biological responses. The Shannon-Wiener biodiversity index increased for plankton and zoobenthos. Furthermore, the density of Cyanophyta decreased by 57.33 %, and the emergence of a substantial population of Chlorophyta and Bacillariophyta contributed to a balance algal facies. Additionally, the average density of zooplankton increased fivefold, while the density of zoobenthos decreased slightly. PMAHRM devices, utilizing newly developed TGB materials, played a pivotal role in aquatic habitat restoration, thereby fostering the sustainable development of aquatic ecosystems.

Conductive hollow hydrogel fibers toward high-sensitivity bio-textiles

Conductive hollow hydrogel fibers toward high-sensitivity bio-textiles

Study of thermally conductive polyurethane/boron nitride composite fibers: Fabrication, characterization, properties and textile applications

AbstractPolyurethane resin (PU) and boron nitride (BN) are used to develop a series of boron nitride/polyurethane (BN/PU) composite fibers by a wet‐spinning method. The thermal conductivity of the composite fibers was improved by blending modified thermally conductive particles with polymer. The improvement of thermal conductivity depends largely on the interfacial effect between them. The results show that PU composite fabric filled with BN functionalized with polyethylenimine and glutaraldehyde (GPBN/PUF) has a high thermal conductivity, revealing an increase of 226% compared to the PU fabric. The GPBN/PUF fabric can reduce the simulated skin temperature by 2.3°C compared with conventional cotton fabric. Additionally, the as‐prepared GPBN/PUF fabric possesses good mechanical stability and washability. This work provides a strategy for developing flexible heat‐conducting fabric.Highlights The stability of the PEI coating formed on the BN surface was significantly improved by GA cross‐linking. The composite fiber fabric has improved thermal conductivity and good mechanical properties. The composite fiber fabric can dissipate heat quickly in practical applications.

Covalently bridging graphene edges for improving mechanical and electrical properties of fibers

Assembling graphene sheets into macroscopic fibers with graphitic layers uniaxially aligned along the fiber axis is of both fundamental and technological importance. However, the optimal performance of graphene-based fibers has been far lower than what is expected based on the properties of individual graphene. Here we show that both mechanical properties and electrical conductivity of graphene-based fibers can be significantly improved if bridges are created between graphene edges through covalent conjugating aromatic amide bonds. The improved electrical conductivity is likely due to extended electron conjugation over the aromatic amide bridged graphene sheets. The larger sheets also result in improved π-π stacking, which, along with the robust aromatic amide linkage, provides high mechanical strength. In our experiments, graphene edges were bridged using the established wet-spinning technique in the presence of an aromatic amine linker, which selectively reacts to carboxyl groups at the graphene edge sites. This technique is already industrial and can be easily upscaled. Our methodology thus paves the way to the fabrication of high-performance macroscopic graphene fibers under optimal techno-economic and ecological conditions.

Laser ablation mechanism and performance of glass fiber-reinforced phenolic composites: An experimental study and dual-scale modelling

Both experimental and simulation approaches were employed to investigate the laser ablation mechanism and performances of Glass Fiber Reinforced Phenolic Composites (GFRP). During the ablation process, the difference in thermal conductivities of the glass fibers and the resin matrix as well as their discrepant physical and chemical reactions form a conical ablation morphology. The formation of a residual carbon layer effectively mitigates the ablation rate in the thickness direction. A higher power density results in a faster ablation rate, while a longer irradiation time leads to a larger ablation pit diameter. To account for the variation in thermal conductivity between the fiber and resin, a macro-mesoscale model was developed to differentiate the matrix from the fiber components. Finite element analysis revealed that laser irradiation leads to phenolic decomposition, glass fiber melting vaporization, and residual carbon skeleton evaporation. The dual-scale model exhibits precise prediction capabilities concerning the laser ablation process of GFRP, and its accuracy is confirmed through the comparison of simulation and experimental results for the GFRP laser ablation process. This model provides a feasible method for performance evaluation and lifetime prediction of GFRP subjected to continuous wave laser irradiation.

The copper matrix composite with "sandwich" structure and three-dimensional networks, showcasing significantly improved thermal conducting performance

Copper matrix composites can be used to address the issue of heat dissipation in electronic devices. Nevertheless, the thermal conductivity (TC) of carbon fiber (CF)/copper (Cu) composites falls significantly below expectations. This is primarily attributed to the challenge of achieving a well-ordered arrangement of CF within the matrix, coupled with the issue of low interfacial bonding strength. A highly effective and uncomplicated approach to fabricate copper matrix composites featuring a "sandwich structure" of Cu-CF-Cu is introduced in this paper. This configuration, achieved through structural design facilitated by hot-press sintering and vacuum suction filtration, exhibited a three-dimensional graphene-like networks (3D-GLNs) and meticulously ordered CF layers over long distances. More importantly, in comparison to pure copper (350 W m−1 K−1), the laminated composite with 40 vol% CF of the CF layer had an in-plane TC of 510 W m−1 K−1, which was approximately 1.5 times greater than that of pure copper. Additionally, the coefficient of thermal expansion (CTE) of the laminated composite with 45 vol% was 9.98 ppm/K. The in-plane TC of the composite was comparable to that of the graphene/Cu composites with the same content. This underscores the advantages of the structural design, even in cases where the TC of the reinforced phase differs by a factor of two. The aforementioned findings demonstrate that this methodology for developing a unique "sandwich" structure can effectively enhance in-plane TC in CF/metal composites, presenting potential for utilization in electronic packaging requiring efficient directional heat transfer.

Type 2 diabetes foot inflammation prevention reminder socks

It is not easy to determine the time between diagnosis and inflammation in patients with type 2 diabetes foot disease. In severe cases, it can lead to ulceration or even amputation. During the development of the inflammation, there will be changes in temperature and blood oxygen saturation in the sole of the foot. Therefore, early monitoring can be an effective prevention and reminder. By integrating flexible conductive fibres, conductive ink and fabric, six nodes on the sole of the foot are monitored. Blood oxygen is monitored above the thumb using photoelectric sensors. The monitoring data signals from these two areas are transmitted to the integrated sensor on the top of the socks and then to the mobile app via Bluetooth. Blood oxygen saturation and temperature can be displayed in real time, and the data is also uploaded to ports such as doctors, communities and hospitals for clinical diagnosis. This study can effectively monitor and remind the inflammatory changes after diabetic foot disease, and change the way of health monitoring by design. Although this study does not have the function of treatment, it is the greatest value of designing intervention medical health - prevention reminder.

Architecture of conductive fibers in pigtails for high‐sensitivity monitoring of structural health in fiber‐reinforced composites

AbstractStructural health monitoring is vital for improving the safety and reliability of fiber‐reinforced composites. However, it is still challenging to achieve high sensing performance without changing the overall properties of composites. In this work, conductive fibers were braided into pigtails to achieve high sensing sensitivity and maintain low electrical resistance. Conductive pigtails with hierarchical and critically connected percolation networks were integrated with basalt fabric by an embroidery technique to realize self‐diagnosis of composites. After being embedded in epoxy composites, the material exhibited low electrical resistance (128.8 kΩ) and excellent sensing performance, demonstrating a high Gauge factor of 8.1, good linearity (R2 > 99%) and stability. The experimental results also showed that conductive pigtails can sensitively inform crack initiation and growth inside composites, which is extremely important for warning of the risk of material fractures. In addition, the mechanical strength of the material was almost unchanged before and after the pigtails were embedded. All these results indicate that conductive pigtails could be used as highly sensitive sensors for realizing structural health monitoring in fiber‐reinforced composites.Highlights CBs/TPU pigtails with hierarchical conductive paths were fabricated and firmly integrated with basalt fabric by the embroidery technique. There is a good interface between the pigtails and the matrix, resulting in the embedding of the pigtails with little change in the mechanical properties of the composites. Pigtails can sensitively detect crack initiation and growth in composites, demonstrating the potential for self‐diagnosis of fiber‐reinforced composites.