Conductive Composite Fibers Research Articles

Efficient Solution Blow Spinning of PAN-CNTs Nanofiber-Based Pressure Sensors with Sandwich Structures.

High-performance sensors play a crucial role in smart wearable technology and human-machine interaction. However, traditional metal- and silicon-based sensors face drawbacks, including limited flexibility, high cost, degradation issues, and insufficient sensitivity. Conductive composite fibers were produced using the spinning solution of PAN and PVB mixed with CNTs and spun at a flow rate of 20 mL·h-1. PAN-CNTs fiber felt formed a sandwich structure by impregnating CNTs aqueous solution, mechanical pressing, and coating graphene. A cost-effective PAN-CNTs nanofiber-based pressure sensor (PCPS) was developed, demonstrating excellent flexibility, conductivity, sensitivity, mechanical properties, and biocompatibility. Nanofiber-based pressure sensors exhibited high sensitivity, with an approximately 75% relative resistance change under a 1 N pressure load. They can withstand 360° bending and have a rapid response time of about 160 ms. PCPS holds significant potential for flexible electronics, smart wearables, and micropressure detection.

Fabrication of conductive polyimide/metal composite fibers for high temperature EMI shielding

Surface metallization of high-performance polymer fibers via electroless plating represents a significant advancement in producing lightweight, flexible and durable electromagnetic interference (EMI) shielding fabrics. The conventional process for metallization of polyimide (PI) fibers faces challenges, including complex procedures and insufficient interfacial adhesion between the metal layer and fiber matrix. Herein, carboxylate-containing PI (PIC) fibers were developed to mitigate the mechanical degradation caused by traditional alkaline etching. Conductive composite fibers (PIC/Cu) were successfully produced through a continuous electroless copper plating process. The robust PIC/Cu interfacial bonding achieved based on nanoscale mechanical interlocking through Ni nanoparticles imparts excellent flexibility and durability, evidenced by only a 4 % increase in electrical resistance after 5000 bending cycles. The dense, uniform copper layer provides high conductivity (1.3 × 104 S/cm), resulting in an optimal EMI shielding efficiency of 63.4 dB for the corresponding fabric. Moreover, PIC/Cu-Ni fibers prepared by further electroless plating of nickel layer on the surface of PIC/Cu fibers demonstrate remarkable electrical stability across temperatures ranging from 50 to 350°C, with only a 1.2 % reduction in conductivity after exposure to 350°C for 1 h. These findings advance the development of high-performance conductive PI fibers for applications in aerospace vehicles and high-temperature environments.

Stiff gel-protected fiber-shaped supercapacitors based on CNFA/silk composite fiber with superhigh interference-resistant ability as self-powered temperature sensor

The development of self-powered sensors with interference-resistant detection is a priority area of research for the next generation of wearable electronic devices. Nevertheless, the presence of multiple stimuli in the actual environment will result in crosstalk with the sensor, thereby hindering the ability to obtain an accurate response to a singular stimulus. Here, we present a self-powered sensor composed of silk-based conductive composite fibers (CNFA@ESF), which is capable of energy storage and sensing. The fabricated CNFA@ESF exhibits excellent mechanical performance, as well as flexibility that can withstand various deformations. The CNFA@ESF provides a good areal capacitance (44.44 mF cm−2), high-rate capability, and excellent cycle stability (91 % for 5000 cycles). In addition, CNFA@ESF also shows good sensing performance for multiple signals including strain, temperature, and humidity. It was observed that the assembly of the symmetrical device with a stiff hydrogel surface layer for protection enabled the real-time, interference-free monitoring of temperature signals. Also, the CNFA@ESF can be woven into fabrics and integrated with a solar cell to form a self-powered sensor system, which has been proven to convert and store solar energy to power electronic watches, indicating its huge potential for future wearable electronics.

Dynamic Adaptive Wrinkle‐Structured Silk Fibroin/MXene Composite Fibers for Switchable Electromagnetic Interference Shielding

AbstractFlexible and dynamic adaptive conductive composite fibers are demanded for functional fabrics and wearable devices, yet the weak interfaces often impair the critical performances for complicated application scenarios. Here, a general and scalable strategy is proposed to construct robust and reversible wrinkle structures on regenerated silk fibroin (RSF) fiber with 2D nanomaterials (i.e., MXene, graphene) by wet‐spinning technique. The dynamic conformation transition of silk fibroin and the core‐shell modulus mismatching together are responsible for the formation of wrinkled structures. Then, it effectively optimizes the interfaces between the assembled nanomaterials and fiber substrate, which significantly reinforce the fibers, complete conductive pathways, and endow exceptional robustness and durability. The MXene‐based fiber shows a high conductivity of ≈1125 S cm−1, far superior tensile strength of 214.3 ± 6.8 MPa and toughness of 15.2 ± 1.5 MJ m−3 as compared to RSF fiber. More interestingly, the transformable wrinkled structure further modulates surface behaviors and properties of the fibers, such as the switchable shielding performances from “off‐state” to “on‐state” induced by humidity. Additionally, the integration of mechanical flexibility and outstanding capacitance (≈829 F cm−3) further expects the great promise of MXene‐based fibers for self‐powered wearable electronics, and intelligent fabrics.

Solution spun electrically conductive nylon 6/poly(pyrrole) nanotubes-based composite fibers

Wearable electronic device applications require flexible polymer-based conducting fibers. Towards this, various conductive fillers have been used in a polymer matrix. However, it usually requires the addition of a high amount of fillers. In this study, electrically conductive composite fibers of nylon 6 (Ny)-poly(pyrrole) nanotubes (PPyNTs) have been demonstrated using the solution-spinning process. The high aspect ratio of PPyNTs can provide a good electrically conductive network and show a percolation threshold at a low concentration of PPyNTs in a nylon matrix. The composite fibers exhibited good DC electrical conductivity of ∼0.002 S/cm at only 6 wt% of PPyNTs. The influence of PPyNTs concentration on the morphology, physical, chemical, and electrical properties of the fibers have been investigated.

A novel structural design of cellulose-based conductive composite fibers for wearable e-textiles

Cellulose-based conductive composite fibers hold great promise in smart wearable applications, given cellulose's desirable properties for textiles. Blending conductive fillers with cellulose is the most common means of fiber production. Incorporating a high content of conductive fillers is demanded to achieve desirable conductivity. However, a high filler load deteriorates the processability and mechanical properties of the fibers. Here, developing wet-spun cellulose-based fibers with a unique side-by-side (SBS) structure via sustainable processing is reported. Sustainable sources (cotton linter and post-consumer cotton waste) and a biocompatible intrinsically conductive polymer (i.e., polyaniline, PANI) were engineered into fibers containing two co-continuous phases arranged side-by-side. One phase was neat cellulose serving as the substrate and providing good mechanical properties; another phase was a PANI-rich cellulose blend (50 wt%) affording electrical conductivity. Additionally, an eco-friendly LiOH/urea solvent system was adopted for the fiber spinning process. With the proper control of processing parameters, the SBS fibers demonstrated high conductivity and improved mechanical properties compared to single-phase cellulose and PANI blended fibers. The SBS fibers demonstrated great potential for wearable e-textile applications.

Statistical modeling enabled design of high-performance conductive composite fiber materials for energy harvesting and self-powered sensing

Fiber-based triboelectric nanogenerators (TENGs) composed of conductive electrode and triboelectric materials are capable of converting mechanical energy into electricity. Core-spun yarn provides a unique structure for preparing composite fibers to resolve the problem of interfacial failure between conductive layer and triboelectric layer for fiber-based TENGs. However, the underlying relationship between interactive parameters and its performance has not been understood that hinders the further developments. Herein, a statistical modeling enabled design was developed for high-performance conductive composite fiber (CCF) for energy harvesting and self-powered sensing. Interactive preparation parameters of CCF-based triboelectric nanogenerator (CCF-TENG) was studied via a statistical strategy combing fractional factorial design (FFD) and response surface methodology (RSM) for exploring the underlying relationships between parameters and properties of CCF-TENG. The two methods could effectively reduce the number of experiments and optimize the preparation parameters, facilitating the design of high-performance CCF-TENGs. The optimized CCF-TENGs could not only be applied to drive LEDs and calculator, but also attached on human body as wearable sensors and even connected with a Bluetooth system for wireless monitoring. Our proposed statistical modeling enabled strategy provide new insights in exploring quantitative underlying relationships for advanced applications of functional materials with optimized performance and desired functionalities.

Regulation of nerve cells using conductive nanofibrous scaffolds for controlled release of Lycium barbarum polysaccharides and nerve growth factor.

Currently, more and more patients suffer from peripheral nerve injury due to trauma, tumor and other causes worldwide. Biomaterial-based nerve conduits are increasingly recognized as a potential alternative to nerve autografts for the treatment of peripheral nerve injury. However, an ideal nerve conduit must offer topological guidance and biochemical and electrical signal transduction mechanisms. In this work, aligned conductive nanofibrous scaffolds comprising polylactic-co-glycolic acid and multiwalled carbon nanotubes (MWCNTs) were fabricated via coaxial electrospinning, and nerve growth factor (NGF) and Lycium barbarum polysaccharides (LBP) purified from the wolfberry were loaded on the core and shell layers of the nanofibers, respectively. LBP were confirmed to accelerate long-distance axon regeneration after severe peripheral nerve injury. In addition, the synergistic promotion of LBP and NGF on nerve cell proliferation and neurite outgrowth was demonstrated. MWCNTs were introduced into the aligned fibers to further increase the electrical conductivity, which promoted the directional growth and neurite extension of neurons in vitro. Further, the combination of conductive fibrous scaffolds with electrical stimulation that mimics endogenous electric fields significantly promoted the differentiation of PC12 cells and the axon outgrowth of neurons. Based on robust cell-induced behaviors, conductive composite fibers with optimized fiber alignment may be used for the promotion of nerve recovery.

Scalable preparation of MWCNTs/PAN conductive composite fibers with Tai Chi structure for thermotherapy textiles

Compared with traditional clothing, wearable textiles with physiotherapy were a breakthrough innovation, among which fiber materials with good mechanical properties and excellent electrical conductivity were key. Herein, we prepared profiled conductive composite fibers (PCFs) with Tai Chi structure based on the polyacrylonitrile (PAN) and carboxylic multiwall carbon nanotubes (MWCNTs) by wet spinning, achieving the synchronous improvement of mechanical and conductivity under a small quantity of conductive fillers doped. By changing the angle of spinning, the migration of MWCNTs could be induced and controlled, realizing the preparation of Tai Chi structure. The PAN and MWCNTs were enriched into the axial unilateral of fibers respectively, similar to the Tai Chi structure, when the spinning angle was 30°. The special Tai Chi structure could concentrate carriers to form a continuous and interpenetrating conductive path and retained the good flexibility and tensile strength of composite fibers. The PCFs prepared with 6 wt% MWCNTs loading possessed 51.6 S/cm and 291 MPa. The wearable electric heaters prepared by PCFs could get a comfortable temperature (30 °C ∼ 60 °C) under the safe voltage condition and had good repeatability and stability, which was expected to provide valuable reference for the development of thermotherapy textiles.

Electromechanical Performance of Strain Sensors Based on Viscoelastic Conductive Composite Polymer Fibers.

Flexible conductive polymer composite (CPC) fibers that show large changes in resistance with deformation have recently gained much attention as strain-sensing components for future wearable electronics. However, the electrical resistance of these materials decays with time during dynamic cyclic loading, a deformation performed to simulate their real application as strain sensors. Despite the extensive research on CPC fibers, the mechanism leading to this decay in the electromechanical response under repetitive cycles remains unreported. Herein, this behavior is investigated using fiber-based strain sensors wet spun from thermoplastic polyurethane (TPU) consisting of a carbonaceous hybrid conductive filler system of carbon black (CB) and carbon nanotubes (CNTs). We found electrical viscosity to predict the observed electromechanical resistance decay. This implies that cycling these materials enables the relaxation of both the polymer chains and the conductive network. In addition, the resulting piezoresistive fibers are sensitive to deformation in the region of low strain (gauge factor of 6.0 within 3.0% strain), remain conductive under 280.5% deformation, and are stable for more than 2000 cycles. Finally, we demonstrate the potential of TPU/CB-CNT fibers as strain sensors for monitoring human motion.

Conductive electrospun composite fibers based on solid-state polymerized Poly(3,4-ethylenedioxythiophene) for simultaneous electrochemical detection of metal ions.

Conductive composite fibers containing poly (3,4-ethylenedioxythiophene) (PEDOT) and silver nanoparticles (AgNPs) were fabricated by emulsion electrospinning of 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) in toluene together with aqueous solution of poly (vinyl alcohol) (PVA) and silver nanoparticles (AgNPs) in the presence of sodium dodecylsulfate followed by heat treatment at 70°C to convert DBEDOT to conductive PEDOT via solid state polymerization (SSP). The composite fibers were characterized by scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and thermogravimetric analysis. The PEDOT/PVA/AgNPs composite fibers deposited on a screen-printed carbon electrode (SPCE) surface exhibited good electrochemical response and was applied for simultaneous detection of heavy metal ions in a mixture, namely Zn(II), Cd(II), and Pb(II) via square wave anodic stripping voltammetry (SWASV). With added Bi+3 into the detection system, the bismuth film formed on the electrode allows effective alloy formation with the deposited heavy metals obtained upon reduction of the heavy metal ions, the detection of heavy metal ions after stripping was successfully accomplished with a linear range of 10-80ppb and limits of detections (LOD) of 6, 3 and 8ppb for Zn(II), Cd(II), and Pb(II), respectively.

Wet-Spun Side-by-Side Electrically Conductive Composite Fibers

Electrically conductive fibers play an important role in smart electronic textiles to connect the key components of a smart system, convey energy, and sometimes serve as a sensor. Polymers for traditional fibers are insulating. Incorporating conductive fillers to produce blend fibers is a common method to produce conductive flexible fibers. In the filler/polymer blend system, increasing the filler load enhances fiber conductivity but that adversely affects fiber processability and deteriorates the fiber mechanical performance. In this study, an innovative wet spinning technique was used to manufacture heterostructured polyacrylonitrile (PAN) and polyaniline (PANI) conductive fibers. A PAN/PANI blend solution was co-spun with a neat PAN solution to produce side-by-side (SBS) fibers. The results showed that, by employing the SBS technique, PAN/PANI solutions of high PANI load that were not spinnable by themselves could be co-spun into SBS fibers with neat PAN. The SBS fibers maintained a similar level of conductivity to the fibers produced from the PAN/PANI blend solution only, although the overall PANI load in the SBS fiber was much lower. Additionally, the SBS fibers exhibited superior mechanical performance with the neat PAN serving as a substrate. The study demonstrated a manufacturing technique to produce conductive polymer composite fibers for e-textiles.

Highly integrated, scalable manufacturing and stretchable conductive core/shell fibers for strain sensing and self-powered smart textiles

Although the research in triboelectric nanogenerator (TENG) textiles has seen a rapid development recently, their integrated and mass fabrication process is still challenging, which hinders its further applications for wearable sensors. Herein, highly integrated and scalable manufacturing conductive composite fibers for weaving TENGs are presented, which might overcome the major problems. The fibers possess liquid alloy/silicone rubber core/shell structures made by simultaneously injecting liquid alloy and silicone rubber into the separate input ports of a coaxial needle, followed by automatically assembled from the output. The liquid alloy/silicone rubber core/shell fiber (LCF) has both good pliability and high resistance-strain sensitivity, which is beneficial for serving as strain sensors directly, and for incorporating with woven for textile-TENGs (t-TENGs)-based self-powered sensoring application. As a result, the open-circuit voltage (Voc), short-circuit current (Isc), short-circuit transferred charge (Qsc) and maximum power density of 4 × 4 cm2 t-TENG are 175 V, 15 μA, 66 nC and 469 mW/m2, respectively. Additionally, the t-TENG is mechanically robust, chemically stable and easy-cleaning for daily use. The wearable t-TENG devices can be used to detect human motions. This work provides a novel method of scalable manufacturing LCFs for weaving wearable t-TENGs, contributing to the development of t-TENGs and wearable self-powered sensors.

Conductive Composite Fiber with Customizable Functionalities for Energy Harvesting and Electronic Textiles.

A fiber-based triboelectric nanogenerator (F-TENG) is an important technology for smart wearables, where conductive materials and triboelectric materials are two essential components for the F-TENG. However, the different physicochemical properties between conductive metal materials and organic triboelectric materials often lead to interfacial failure problems, which is a great challenge for fabricating high-performance and stable F-TENGs. Herein, we designed a new conductive composite fiber (CCF) with customizable functionalities based on a core-spun yarn coating approach, which was applicable for a fiber-based TENG (CCF-TENG). By combing a core-spun method and a coating approach, triboelectric materials could be better incorporated on the surface of conductive fibers with the staple fibers to form a new composite structure with enhanced interfacial properties. The applicability of the method has been studied using different conductive and staple fibers and coating materials as well as different CCF diameters. As a demonstration, the open-circuit voltage and power density of the CCF-TENG reached 117 V and 213 mW/m2, respectively. Moreover, a 2D fabric TENG was woven and used as a wearable sensor for motion detection. This work provided a new method for 1D composite fibers with customizable functionalities for the applications in smart wearables.

Lightweight, Robust, Conductive Composite Fibers Based on MXene@Aramid Nanofibers as Sensors for Smart Fabrics.

Developing one-dimensional fiber-based sensors to meet the requirement of spinnability, portability, flexibility, and easeful conformability in smart wearable devices has attracted increasing interest. Here, we report highly conductive MXene@aramid nanofibers (ANFs) with a distinct skin-core structure by the wet spinning method. MXene, an emerging 2D conductive material, is applied to build internal conductive paths. ANF frameworks function as protective and skeleton structures to reduce the fiber oxidation probability and achieve superior strength. The obtained MXene@ANF fiber with superior conductivity (2515 S m-1) and tensile strength (130 MPa) works as a promising sensor for smart fabrics to detect different human movements with abundant detection motions, fast response time (100 ms), and long service life (up to 1000 cycles). Benefiting from its high flexibility, it can be sewn into textile and gloves as a smart wearable device. Besides superior thermal stability, it shows promising electrothermal properties with wide heating temperature (25-123 °C) and fast heating temperature (10 s). Therefore, the MXene@ANF fiber with the skin-core structure shows great potential as a promising sensor to be applied in electric heating and smart wearable fabrics.

Electronic Textiles Based on Highly Conducting Poly(vinyl alcohol)/Carbon Nanotube/Silver Nanobelt Hybrid Fibers.

Highly stable conducting fibers have attracted significant attention in electronic textile (e-textile) applications. Here, we fabricate highly conducting poly(vinyl alcohol) (PVA) nanocomposite fibers with high thermal and chemical stability based on silver nanobelt (AgNB)/multiwalled carbon nanotube (MWCNT) hybrid materials as conducting fillers. At 20 vol % AgNB/MWCNT, the electrical conductivity of the fiber dramatically increased (∼533 times) from 3 up to 1600 S/cm after thermal treatment at 300 °C for 5 min. Moreover, PVA/AgNB/MWCNT fiber resists the harsh conditions of good solvents for PVA as well as high temperatures over the melting point of PVA, whereas pure PVA fiber is unstable in these environments. The significantly enhanced electrical conductivity and chemical stability can be realized through the post-thermal curing process, which is attributed to the coalescence between adjacent AgNBs and additional intensive cross-linking of PVA. These remarkable characteristics make our conducting fibers suitable for applications in e-textiles such as water leakage detectors and wearable heaters. In particular, heating behavior of e-textiles by Joule heating can accelerate the desorption of physically trapped moisture from the fiber surface, resulting in the fully reversible operation of water leakage monitoring. This smart e-textile sensor based on highly stable and conductive composite fibers will pave the way for diverse e-textile applications.

Conductive Composite Fiber with Optimized Alignment Guides Neural Regeneration under Electrical Stimulation.

Conductivity and alignment of scaffolds are two primary factors influencing the efficacy of nerve repair. Herein, conductive composite fibers composed of poly(ɛ-caprolactone) (PCL) and carbon nanotubes (CNTs) with different orientation degrees are prepared by electrospinning at various rotational speeds (0, 500, 1000, and 2000 rpm), and meanwhile the synergistic promotion mechanism of aligned topography and electrical stimulation on neural regeneration is fully demonstrated. Under an optimized rotational speed of 1000 rpm, the electrospun PCL fiber exhibits orientated structure at macroscopic (mean deviation angle = 2.78°) or microscopic crystal scale (orientation degree = 0.73), decreased contact angle of 99.2° ± 4.9°, and sufficient tensile strength in both perpendicular and parallel directions to fiber axis (1.13 ± 0.15 and 5.06 ± 0.98 MPa). CNTs are introduced into the aligned fiber for further improving conductivity (15.69-178.63 S m-1 ), which is beneficial to the oriented growth of neural cells in vitro as well as the regeneration of injured sciatic nerves in vivo. On the basis of robust cell induction behavior, optimum sciatic nerve function index, and enhanced remyelination/axonal regeneration, such conductive PCL/CNTs composite fiber with optimized fiber alignment may serve as instructive candidates for promoting the scaffold- and cell-based strategies for neural repair.

Wearable Electronics: Self‐Bondable and Stretchable Conductive Composite Fibers with Spatially Controlled Percolated Ag Nanoparticle Networks: Novel Integration Strategy for Wearable Electronics (Adv. Funct. Mater. 49/2020)

Wearable Electronics: Self‐Bondable and Stretchable Conductive Composite Fibers with Spatially Controlled Percolated Ag Nanoparticle Networks: Novel Integration Strategy for Wearable Electronics (Adv. Funct. Mater. 49/2020)

Self‐Bondable and Stretchable Conductive Composite Fibers with Spatially Controlled Percolated Ag Nanoparticle Networks: Novel Integration Strategy for Wearable Electronics

AbstractAdvances in electronic textiles (E‐textiles) for next‐generation wearable electronics have originated from making a balance between electrical and mechanical properties of stretchy conductive fibers. Despite such progress, the trade‐off issue is still a challenge when individual fibers are woven and/or stretched undesirably. Time‐consuming fiber weaving has limited practical uses in scalable E‐textiles. Here, a facile method is presented to fabricate ultra‐stretchable Ag nanoparticles (AgNPs)/polyurethane (PU) hybrid conductive fibers by modulating solvent diffusion accompanied by in situ chemical reduction and adopting a tough self‐healing polymer (T‐SHP) as an encapsulation layer. First, the controlled diffusivity determines how formation of AgNPs is spatially distributed inside the fiber. Specifically, when a solvent with large molecular weight is used, the percolated AgNP networks exhibit the highest conductivity (30 485 S cm−1) even at 300% tensile strain and durable stretching cyclic performance without severe cracks by virtue of the efficient strain energy dissipation of T‐SHP encapsulation layers. The self‐bondable properties of T‐SHP encapsulated fibers enables self‐weavable interconnects. Using the new integration, mechanical and electrical durability of the self‐bonded fiber interconnects are demonstrated while stretching biaxially. Furthermore, the self‐bonding assembly is further visualized via fabrication of a complex structured E‐textile.

Covalently linked polydopamine-modified boron nitride nanosheets/polyimide composite fibers with enhanced heat diffusion and mechanical behaviors

Polymer fibers with high tensile strength and high thermal conductivity (k) are attractive in next-generation thermoregulating textiles, wearable electronic devices and so on. However, most polymeric fibers usually have a low thermal conductivity below 0.5 W m−1 K−1, hardly satisfying the high requirements for thermal management. Herein, we report an effective approach to achieve a highly thermally conductive and high-strength polyimide (PI) composite fibers containing the polydopamine modified boron nitride nanosheets (PDA@BNNS). The uniform dispersion of nanofiller, covalent adhesion of PDA@BNNS to PI matrix and highly aligned PDA@BNNS network are successfully realized during in-situ polymerization, wet-spinning and post hot-drawing process. Thus, significant improvements in the heat diffusion behavior and mechanical property for PI/PDA@BNNS composite fibers are achieved. The incorporation of a very low content of PDA@BNNS (~0.5 wt%) results in a 27% increase in thermal conductivity for the PI/PDA@BNNS-0.5 composite fiber. An optimum thermal conductivity of 3.44 W m−1 K−1 for the composite fiber is obtained with 10 wt% nanofiller addition, and meanwhile, the tensile strength and modulus approach 1.8 GPa and 100.7 GPa, respectively, far exceeding most of the BNNS containing composite fibers. Additionally, these composite fibers are scalable and weavable, making them good candidates for the future advanced functional textiles or as the reinforcement in thermally conductive composites applications.