Core-sheath Yarns Research Articles

Electro–Centrifugal Spinning of Core–Sheath Composite Yarns with Micro/Nano Structures for Self–Powered Sensing

In recent years, triboelectric nanogenerators (TENGs) have garnered extensive attention in the realm of self-powered sensors due to their capability to harness low-frequency mechanical energy. Among these, textile-based triboelectric nanogenerator stands out as a pivotal platform for wearable sensing. Nevertheless, conventional approaches, such as directly coating triboelectric materials on fabrics, often compromise the inherent properties. In this study, we utilized our self-developed electro-centrifugal spinning equipment to continuously fabricate core-sheath yarns with micro/nano structures, resulting in the development of pocket-shaped fabric-based (PF) TENGs. This innovative design preserves the original softness and breathability of the fabric while delivering substantial electrical output owing to its layered structure and extensive specific surface area. PF–TENGs can accurately detect electrical output signals from various motion states. This electro–centrifugal spinning technology offers new research directions and sensing application prospects for self-powered smart textile development.

Excellent thermal, moisture-permeable weft-knitted fabric with core-sheath yarn structure for foot protection in cold environments

In extremely cold environments, maintaining body temperature and reducing heat dissipation is essential for maintaining human health and life safety, but the field of thermal insulation shoe upper fabric has not been deeply studied. In this paper, based on the dual-scale structure of the yarn and shoe upper fabric, a composite yarn with a core-sheath structure is designed, and a using plating stitch pattern weft-knitted whole garment thermal insulation shoe upper fabric with double-layer structure is proposed. By testing the mechanical properties and thermal and moisture performance of the shoe upper fabric and the thermal insulation performance of the whole shoe, the thermal insulation mechanism of the weft-knitted whole garment shoe upper fabric with a double-layer structure and dual-scale structure design was systematically studied. The results show that the shoes made of polyimide/hollow polyester composite yarn with core-sheath structure yarn have good thermal insulation performance. The use of core-sheath yarns can improve the thermal insulation performance of the shoe, and, with the increase of the ratio of core-sheath yarn, the thermal insulation performance of the shoe is better. Starting from the dual-scale shoe fabric structure, this article proposes a novel method for the industrial production of thermal insulation shoe upper fabrics, which is expected to provide guidance for the further development of thermal insulation shoe upper fabric in the future.

Wet-adaptive Strain Sensor Based on Hierarchical Core-sheath Yarns for Underwater Motion Monitoring and Energy Harvesting

Bifunctional flexible electronics with motion monitoring and energy harvesting have broad application prospects in day-to-day activities of human society. Nevertheless, conventional electronics are difficult to adapt to the wear comfortability and anti-sensing interference properties in wet environments. Herein, a wet-adaptive spandex/graphene@cotton/polyurethane yarn (SGCPY) sensor is fabricated with excellent sensing and triboelectric performance, which comprises core layer of spandex fibers, middle layer of graphene@cotton sensing fibers and outer layer of spindle-knotted polyurethane nanofibers. Benefiting from its unique structure, as-prepared SGCPY sensor exhibits high mechanical properties (~80%), superhydrophobic performance (>130°), good strain sensitivity (1.82) and fatigue resistance (12000 cycles) even under water condition. The usage of the SGCPY sensor is demonstrated for the stable monitoring of human body motions and human-machine interaction in both air and water environments. When SGCPY sensor weave as plain fabric, the textile also can convert various mechanical energy into electric power for driving electronic device, showing a maximum voltage of ~3.9V and ~0.7V with solid-solid and liquid-solid contact. This work fosters the in-depth study of textile-based electronics for underwater applications and highlights the promising prospects of multi-functional flexible electronics based on textiles.

Heat-resistant core-sheath yarn sensor with high durability and thermal adaptivity for fire rescue

Heat-resistant core-sheath yarn sensor with high durability and thermal adaptivity for fire rescue

Friction spun spandex/rGO/Ag/polyester core-sheath yarn with antibacterial activity for wearable sensors

Wearable sensors, which feature textile substrates integrated with conductive layers, have received increasing attention from researchers due to their huge potential in health management. However, the inevitable damage of conductive layer caused by friction and bacterial growth on the textile substrate during its direct contact with bare skin are still the issues that hinder the long-term service of wearable sensors. Herein, a core-sheath yarn was prepared by wrapping polyester (PET) fibers coated with reduced graphene oxide (rGO)/silver nanoparticles (Ag NPs) around the spandex filaments via friction spinning. The core-sheath structure guarantees good prevention of the interface composed of rGO and Ag NPs in between from friction, while the introduction of Ag NPs ensures antibacterial activity of the yarn. The morphology and chemical composition of the nanomaterials deposited on the surface of PET fibers was investigated to reveal the sensing mechanism of the yarn. Meanwhile, its sensing performance was comprehensively evaluated from the perspectives of sensitivity, durability and comparison of commercial ECG. Despite the fact that inevitable damage of the rGO/Ag layer occurred during the friction spinning process, the core-sheath yarn still featured a gauge factor of 8.11 and a threshold of sensing range up to 68.57 %. Apart from being able to detect respiratory signals, cardio signals with the frequency of 70 beat per min (bpm) was also recorded. Compared to signals with the frequency of 73 bpm recorded by a commercial ECG sensor simultaneously, the core-sheath yarn exhibited satisfying precision. Moreover, the existence of Ag NPs in the conductive interface endowed the yarn with ability to yield 13-mm and 15-mm wide growth inhibition zones of E. coli and S. aureus, respectively. The cardiorespiratory sensing ability coupled with antibacterial activity of the yarn suggested its satisfying sensitivity and prolonged service time, making it a promising wearable sensor subjected to direct skin contact for long-time cardiorespiratory monitoring.

Programmable 3D bifurcated braided structures for system-adaptable and integrated triboelectric sensing

Textiles are a flexible framework for devising soft triboelectric nanogenerators (TENGs) that can monitor or harvest mechanical energy generated from body motion. Despite various structures and impressive performance, integrated textile TENGs that can regulate the contact-separation between triboelectric materials are rarely explored. Herein, we report a programmable three-dimensional (3D) braiding strategy to construct Y-profile bifurcated textile TENGs (3D Y-TENG) by the industry-compatible hexagonal braider. Through the regulation of interlaced and bifurcated regions along 3D Y-TENGs, different contact-separations can be obtained. 3D Y-TENGs were constructed by braiding two sets of core-sheath yarns with nylon and polytetrafluoroethylene (PTFE) as the triboelectric materials, with both yarns exhibiting exceptional abrasion resistance (i.e., 3000 cycles of abrasion without structural disintegration). Five 3D Y-TENG with different bifurcation patterns were designed and fabricated to tailor the contact-separation, all presenting triboelectric response towards mechanical compressing, stretching, and bending. 3D Y-TENGs are featured with remarkable stretchability, softness, flexibility, foldability, and mechanical endurance, enabling their comfortable contact with the human body. This work presents programmable braided structures that can be tailored, adapted, and integrated with different systems for seamless electronic garments.

Large-scalable fabrication of zirconium carbide-based core-sheath yarn for wearable applications

As advances in science and technology highlight the applications of electronic textiles, their reliance on natural resources becomes apparent. To promote sustainability, yarns with strain-sensing and photothermal conversion functions are needed, utilizing recyclable resources effectively. However, current-sensing yarns with photothermal-conversion functions have low photothermal-conversion capabilities. Herein, we report a simple and feasible strategy for fabricating core-sheath-structured yarns with photothermal and sensing capabilities for photothermal conversion and strain-sensing applications. The spinning speed employed in the friction spinning approach exceeded 600 m/h, paving the way for a new method that combines sensing and photothermal properties. The multi-layer yarn included spandex as the core yarn, carbon nanotube-coated cotton as the middle layer, and a zirconium carbide@polyurethane film as the sheath. The obtained spandex/carbon nanotube @cotton/zirconium carbide@polyurethane yarn had good strain sensing ability, and the yarn temperature could be increased to 103.5 °C after 1 min of infrared-light irradiation, being stabilized at 121.7 °C after 5 min. The durability tests demonstrated that the sensing and photothermal capabilities of the yarns were maintained well after cyclic performance test, cyclic friction test and cyclic twist test. The obtained core sheath yarn may provide a feasible way for industrial-scale manufacture wearable electronic devices and smart sensing yarn with excellent sensing and photothermal performance.

Facile construction of a flexible smart core-sheath flax yarns with temperature-responsive resistance for ultra-fast fire-alarm response

In order to improve the fire safety of combustible materials in daily life, the intelligent sensor with high sensitivity and wireless remote warning ability is urgently needed for early real-time fire detection. Herein, the intelligent core-sheath flax-GO/CS/PDA yarn prepared using the electrostatic interaction between graphene oxide (GO) sheets, chitosan (CS) molecules and polydopamine (PDA). According to the rapid reduction of resistance of GO stimulated at high temperature, it is reduced to reduced GO (rGO), forming a conductive network circuit. Due to the effective protection of the GO/CS/PDA layer on the flax yarn, it prevents the exchange of heat and oxygen, and improves the thermal stability and flame retardant of flax yarn. What's more, in the case of assembling 1 trilayer, the prepared intelligent core-sheath yarns achieve sensitive fire warning response time (∼3 s). The results show that the prepared core-sheath flax-GO/CS/PDA intelligent yarn have excellent flame retardancy and super-fast fire response speed at low temperature (<300 ℃). More importantly, the signal processing information received by the fire alarm device is transmitted to the wireless communication device via Bluetooth. Therefore, when the abnormal temperature is detected, the communication equipment will immediately emit an alarm sound. This study provides a new strategy and foresight for realizing the ideal fire performance and real-time temperature warning response time based on GO, and expands the application of GO network in early fire detection and wireless sensor warning.

Scalable Core–Sheath Yarn for Boosting Solar Interfacial Desalination Through Engineering Controllable Water Supply

Tailoring water supply to achieve confined heating has proven to be an effective strategy for boosting solar interfacial evaporation rates. However, because of salt clogging during desalination, a critical point of constriction occurs when controlling the water rate for confined heating. In this study, we demonstrate a facile and scalable weaving technique for fabricating core–sheath photothermal yarns that facilitate controlled water supply for stable and efficient interfacial solar desalination. The core–sheath yarn comprises modal fibers as the core and carbon fibers as the sheaths. Because of the core–sheath design, remarkable liquid pumping can be enabled in the carbon fiber bundle of the dispersed super-hydrophilic modal fibers. Our woven fabrics absorb a high proportion (92%) of the electromagnetic radiation in the solar spectrum because of the weaving structure and the carbon fiber sheath. Under one-sun (1 kW·m−2) illumination, our woven fabric device can achieve the highest evaporation rate (of 2.12 kg·m−2·h−1 with energy conversion efficiency: 93.7%) by regulating the number of core–sheath yarns. Practical application tests demonstrate that our device can maintain high and stable desalination performance in a 5 wt% NaCl solution.

Liquid flow spinning mass-manufactured paraffin cored yarn for thermal management and ultra-high protection

Thermal management and ultra-high protection textiles are critical for polar scientists, astronauts and firefighters. Phase change materials (PCMs) effectively retard huge thermal changes, and thermal damage by absorbing or releasing heat during phase transition. However, due to the materials and engineering challenges inherent in PCMs based textiles, commercial PCMs usually suffer with high rigidity, no-breath-ability, easy leakage and abrasion, limiting their potential applications. Herein, we proposed a mass-producible liquid flow spinning (LFS) method, in which molten paraffin is poured into continuous hollow silicon tubes and then wrapped by staple fibers to form paraffin-coated yarns (PCYs) on a friction spinning frame. The obtained PCYs showed enhanced mechanical properties (break strength of 7.80 N, wear resistance of 2000 cycles) due to the novel core-sheath yarn structure. Besides, thanks to the high melting enthalpy (60.967 J/g) of PCYs, the yarns showed the excellent temperature regulating effect. A double-sided joint PCYs fabric (PCYF) is fabricated to study the PCYs performance further, results show that the PCYF can withstand 10,000 cycles of abrasion without breakage and PCMs leakage. Furthermore, owing to the much gaps provided by the stretch fibers and interweaving points, the fabric exhibits good breathability. In particular, compared with commercial PCMs based textiles, our PCYF is superior in thermal protection performance (9 °C lower). The fireproof performance is also excellent as our PCYF can withstand flame temperatures higher than 1142 °C. The PCYs production method provided here could pave the way for human thermal protection textiles.

Electrical Connection Configurations for Polyvinylidene Fluoride Nanofabrics With Enhanced Piezoelectric Response

Various electrical connection configurations for piezoelectric nanofabrics (PNFs) fabricated from electrospun polyvinylidene fluoride (PVDF) nanofibers and yarns were realized through different electrode designs, including interdigitated wire electrodes, screen electrodes, core-sheath electrodes, and their combinations. The effects of the electrode designs and weaving modes were investigated on the electromechanical performance. It was found that the piezoelectric output of the PNFs in response to mechanical input was significantly improved by increasing the contact area between the electrodes and the active piezoelectric nanofibers, and thus enhancing the connectivity of all the conductive elements in the PNFs. Large output voltage magnitude (~1.4 V) was observed in the PNF samples made of piezoelectric core-sheath yarn with optimized electrode connection and coverage. Our results here clearly prove the high importance of electrical connection configuration to the performance of PNFs. We believe there is a great room to optimize electrode designs and electrical connections for improved piezoelectric fabric sensors and transducers.

Large-scale production of weavable, dyeable and durable spandex/CNT/cotton core-sheath yarn for wearable strain sensors

Yarn-based wearable sensors have attracted attention, but it is difficult to fabricate yarn strain sensors with large-scale production, weavability, dyeability and durability toward real applications as wearable electronics and smart textiles. Herein, we report a facile core spun strategy to fabricated spandex/CNT cotton yarns (SCCY) on an industrial spinning machine. For the first time, wearable sensor could be dyed through a simple dip dyeing process with different colors (red, yellow, blue and black). The unique core-sheath structure endowed the yarn with good sensitivity (gauge factor of 21.85 at 300% strain), broad sensing range (0%-300% strain), excellent durability (against dip dyeing, washing, acid and alkali) and abrasion resistance (resistance change 5% after rubber 100 cycles). The sensor yarn was also successfully woven/knitted into textiles and it could be sewn into a fabric. The weavable and dyeable core-spun yarn in the present work provide a feasible way for industrial-scale manufacture wearable sensors.

Flexible all-textile dual tactile-tension sensors for monitoring athletic motion during taekwondo

Abstract A smart garment as a “second skin,” is the goal to achieve a similar level of multiple stimuli as the quantified sensitivity of skin, and most emerging electronic textiles (E-textiles) simply combined discrete sensors with single function to recognize multiple stimuli. However, such strategy usually leads to complicated stitching E-textiles and unsatisfied wear experience, especially under large strain and pressure deformations. Herein, we propose “all in one” E-textile with a dual tactile and tension stimulus response. This dual response is facilely enabled by a composite textile assembly with core-sheath yarn and spacer fabric. A significant challenge that limits this dual-sensing technology is the so-called “double solution phenomenon” that occurs when the core-sheath yarn demonstrates nonmonotone response along stretching deformation. We solve this challenge by coating the yarns with an insulating polyurethane layer prior to twisting. It is demonstrated that our E-textile exhibits a wide deformation range (up to 90%), a wide pressure detection range (up to 110 kPa), good durability (~100,000 cycles), good hand washability, water vapour permeability, and air breathability. Our fabric-based sensing technology allows for precise monitoring of athletic movement and form, illustrating its potential application in Taekwondo and robust physical training analysis.

Development of metallic core-spun yarns and hybrid conductive fabrics for electromagnetic shielding applications

Various metallic core-sheath yarns have been prepared and conductive fabrics are woven using sample loom for electromagnetic shielding applications. The core-sheath yarn is prepared using stainless steel and polyester slivers with different proportions of SS fibre content. The conductive fabrics are produced with different warp and weft patterns. The shielding effectiveness (SE) of fabric has been tested in the frequency range from 50 MHz to 1.5 GHz according to ASTM D4935. The test results reveal that the fabric with cell type structures shows better shielding effectiveness (SE) than the plain weave structures. The increase in metal content does not influence the SE of fabric having conductive fibres in one direction. However, fabric having conductive fibres in warp and weft directions shows improved shielding effectiveness. When the grid size is increased, the shielding effectiveness is decreased. It is concluded that the fabric with small grid size and cell type weave structures could provide effective shielding as compared to plain woven fabric in low frequency range.

Helical core-sheath elastic yarn-based dual strain/humidity sensors with MXene sensing layer

Flexible, stretchable and sensitive textile-based sensors play important roles in a wide variety of artificial intelligence because of its seamless integration with clothing and good comfort. Herein, MXene sensing layer is deposited on the surface of springlike helical core-sheath polyester yarns thanks to the capillarity effect and its intrinsic hydrophilic ability, and the resultant strain sensor and humidity sensor exhibit wide detection range from 0.3 to 120% strain and 30–100% relative humidity (RH) detection, owing to elastic core-sheath structures. The strain sensor shows excellent reproducibility (over 10000 cycles) and fast response time (120 ms). The core-sheath yarn sensor can detect various human motions such as walking, bending and twisting as well as physiological signal (pulse), which have great potential in real-time precise medicine and health care. The yarn sensor could also be an excellent humidity sensor because of the high specific area structure of yarn and intrinsic hydrophilic properties of MXene sensing layer.

A novel knitted scaffold made of microfiber/nanofiber core-sheath yarns for tendon tissue engineering.

Tendon injury is common in sports and other rigorous activities, which may result in dysfunction and disability. Recently, scaffolds with a knitted structure have been widely applied for tendon tissue engineering. The purpose of this study was to fabricate a novel knitted tendon scaffold made of microfiber/nanofiber core-sheath yarns and evaluate the biocompatibility and the effect of tenogenic differentiation and tendon tissue regeneration in vitro and in vivo. Poly(ε-caprolactone) (PCL) microfibers, PCL microfibers-PCL nanofibers (PCL-PCL) and PCL microfiber-silk fibroin/poly(l-lactic acid-co-ε-caprolactone) nanofiber (SF/PLCL) core-sheath yarns were fabricated and then knitted with an automatic knitting machine to produce PCL, PCL-PCL and PCL-SF/PLCL fabric scaffolds. The characterization of the scaffolds was performed by using scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy and an universal mechanical instrument. The in vitro experiment showed that rabbit bone marrow stem cells seeded on the scaffolds exhibited an elongated morphology and proliferated better in the PCL-SF/PLCL group, as compared to the PCL and PCL-PCL groups. Moreover, the PCL-SF/PLCL scaffold promoted the tenogenic differentiation of the cells for the highest expression levels of the tendon-related genes through down-regulating p-ERK1/2 expression among the three groups. Furthermore, the in vivo study in a rabbit patellar defect model demonstrated that the PCL-SF/PLCL scaffold could enhance the tissue regeneration and remodeling process as indicated by the better structural and biomechanical properties according to the results of histology, immunohistochemistry, transmission electron microscope examination and biomechanical tests. Therefore, the PCL-SF/PLCL scaffold is proved to be a promising biomaterial for tendon tissue engineering and a potential candidate for clinical treatment of tendon injury in the future.

An efficient hybrid strategy for composite yarns of micro-/nano-fibers

In contrast to yarns of micro-fibers and those of nano-fibers, composite yarns composed of micro- and nano-fibers exhibit great potential in functional applications by integrating the respective advantages of multiscale fibers. However, the efficient fabrication of composite yarns remains challenging. So far, the existing nano-fiber included yarns, such as nanofiber yarn and core-sheath yarn, exhibit poor durability and low preparation efficiency. Herein, an efficient hybrid strategy for the composite yarns made of multiscale fibers has been developed by integration of electrospun nano-fibers and webbing of micro-fibers. Polyacrylonitrile nano-fiber/viscose micro-fiber composite yarns have been prepared massively. To explore structure of the resulting composite yarns, fluorescent tracer technique was adopted and revealed that nano-fibers are dispersed within composite yarn uniformly, while the structure of composite yarns can be governed easily by adjusting electrospinning parameters. Compared to pure yarns of viscose micro-fibers, the composite yarns possess mechanical properties at the same level, enabling the weaving, knitting and braiding of it for industrial applications. Furthermore, the formation mechanism of the composite yarn has been investigated and the fibrous adhesion among multiscale fibers has been modeled. The efficient approach should be a promising one for the design and scalable fabrication of composite yarns of micro-/nano-fibers.

Dref-3 yarn structure with plied staple fibrous core

PurposeDref-3 friction spun core yarns produced using staple fibre yarn as the core, e.g. Jute core yarn wrapped with cotton fibre, have poorer mechanical properties compared to the core yarn itself. The purpose of this study was to understand the structure of such yarns, that will lead to the optimization of fibre, machine and process variables for production of better quality yarn from the Dref-3/3000 machines.Design/methodology/approachThe Dref spinning trials were conducted following a full factorial design with six variables, all with two operative levels. The Dref-3 friction spun yarn, in which the core is a plied, twisted ring yarn composed of cotton singles and the sheath, formed from the same cotton fibres making the singles, has been examined. The structures have also been studied by using the tracer fibre technique.FindingsIt was observed that rather than depending on the plied core yarn, the tensile properties of the Dref-3 yarn are significantly determined by the parameters those affect the constituent single yarn tensile properties, i.e. the amount of twist and its twist direction, yarn linear density and the sheath fibre proportion used during the Dref spinning in making the final yarn. Further, when the twist direction of single yarn, double yarn and the Dref spinning false twisting are in the same direction, the produced core-sheath yarn exhibits better tensile properties.Practical implicationsThe understanding of the yarn structure will lead to optimized production of all staple fibre core Dref spun yarns.Social implicationsThe research work may lead to utilization of coarse and harsh untapped natural fibres to the production of value-added textile products.Originality/valueThough an earlier research has reported the effects of sheath fibre fineness and length on the tensile and bending properties of Dref-3 friction yarn, the present study is the first documented attempt using the tracer fibre technique to understand Dref-3 yarn structure with plied staple fibrous core.

Versatile Core–Sheath Yarn for Sustainable Biomechanical Energy Harvesting and Real‐Time Human‐Interactive Sensing

AbstractThe emergence of stretchable textile‐based mechanical energy harvester and self‐powered active sensor brings a new life for wearable functional electronics. However, single energy conversion mode and weak sensing capabilities have largely hindered their development. Here, in virtue of silver‐coated nylon yarn and silicone rubber elastomer, a highly stretchable yarn‐based triboelectric nanogenerator (TENG) with coaxial core–sheath and built‐in spring‐like spiral winding structures is designed for biomechanical energy harvesting and real‐time human‐interactive sensing. Based on the two advanced structural designs, the yarn‐based TENG can effectively harvest or respond rapidly to omnifarious external mechanical stimuli, such as compressing, stretching, bending, and twisting. With these excellent performances, the yarn‐based TENG can be used in a self‐counting skipping rope, a self‐powered gesture‐recognizing glove, and a real‐time golf scoring system. Furthermore, the yarn‐based TENG can also be woven into a large‐area energy‐harvesting fabric, which is capable of lighting up light emitting diodes (LEDs), charging a commercial capacitor, powering a smart watch, and integrating the four operational modes of TENGs together. This work provides a new direction for textile‐based multimode mechanical energy harvesters and highly sensitive self‐powered motion sensors with potential applications in sustainable power supplies, self‐powered wearable electronics, personalized motion/health monitoring, and real‐time human‐machine interactions.

Fabrication of hollow nanofibrous structures using a triple layering method for vascular scaffold applications

This study aims to develop a new approach for fabricating hollow nanofibrous yarns by engineering a triple-layer structure (polyvinyl alcohol (PVA) multifilament core surrounded by a layer of PVA nanofibers and a polylactic acid (PLA) nanofiber outer layer). After fabrication of this 3-layer structure, the core portion was extracted, leaving the outer layer intact after dissolving the PVA nanofibers in water. To determine the optimum thickness of the outer layer, hollow nanofiber yarns with five different thicknesses were produced. A hollow nanofiber yarn was also produced using a common method to enable comparison of the methods. In the common method, a core sheath yarn consisting of a PVA multifilament core and a PLA nanofiber outer layer was fabricated, and a hollow yarn was produced by placing the core yarn in hot water. The results revealed facilitation of core extraction from the yarn body of the new 3-layer structure, which occurred due to rapid dissolution of the middle layer. The wicking behavior in the hollow yarn fabricated using the novel method followed the Locus Washburn equation and that of the hollow yarn produced from the core sheath yarn deviated from it. The results demonstrated that tensile properties of hollow nanofiber yarns were improved by increasing the thickness. Furthermore, hemolysis and cytotoxicity assays indicated that the fabricated hollow nanofibrous structure is non-toxic and blood compatible, indicating its potential for use in biomedical applications such as vascular scaffolds.