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Stretchable yarn strain sensors demonstrate incomparable advantages for application in wearable electronic devices, such as health monitors, interfaces for human–computer interactions, and flexible robots, because of their good flexibility and ease of integration with other components and fabrics. In this study, a graphene oxide (GO)-doped polyacrylonitrile nanofiber-coated hybrid yarn with a uniformly wavy structure was used as the elastic substrate, and an in situ polymerized polypyrrole conductive polymer was applied to the nanofiber surface to construct a highly stretchable yarn strain sensor. The obtained sensor exhibited an advantageous wavy structure, which endowed it with a wide monitoring range of 0–500%. The large number of nanofibers in the wave also provided a large contact area, which endowed the sensor with an outstanding resistance change of 173.13 under stretching. In addition, the sensor could monitor the bending deformation; the bending sensitivity was 16.6 at a bending degree of 4 cm. Meanwhile, the sensor exhibited stable cycle durability, and only a small sensitivity loss rate was evident after 10,000 cycles during stretching and bending. In addition, the sensor exhibited ideal weaveability and integration and could be easily woven into any fabric. Significantly, it could monitor human muscle vibration and body movement, indicating its high potential for application in wearable electronic devices. [ABSTRACT FROM AUTHOR]

Highlights • A novel airflow-electrospinning method to prepare nanofiber-coated hybrid yarn. • Prepared nanofiber-coated hybrid yarn had a uniform and close-knit out-of-plane wavy structure. • The hybrid yarn possessed a high strain of 531.98%. • The method was suitable for the preparation of highly elastic hybrid yarn with low-elastic polymer nanofiber layer. Abstract Nanofiber-coated hybrid yarn not only exhibited the performance advantages of coating nanofiber-layer, but also possessed the structural feature of core layer, which could endow it excellent application prospect. Previous studies for fabricating nanofiber-coated hybrid yarn had limitations of poor yarn structure and discontinuity, and obtained hybrid yarns with a small strain. Herein, a novel stepped airflow-electrospinning method, in which stepped airflow field could effectively control the movement of nanofibers, was proposed to spin continuous nanofiber-coated hybrid yarn. Interestingly, a highly stretchable nanofiber-coated hybrid yarn with uniform wavy structure was obtained by our designed method, achieving an ultra-high strain of 531.98%. [ABSTRACT FROM AUTHOR]

The development of highly sensitive, stretchable, and wearable textile-based electronic skin is of great value for application in human health monitoring, robot skin, and intelligent electronic devices. Here, we construct a highly sensitive and stretchable electronic fabric with a simple and low-cost electrospinning technology that enables us to simultaneously map and quantify the mechanical stresses induced by normal pressure, lateral strain, and flexion and to detect the noncontact finger proximity. The fabric is woven from composite yarns that are formed by a core-spun yarn wound helically around the surface of the elastic thread, wherein the core-spun yarn is obtained by coating a graphene (GO)-doped polyurethane (PU) nanofiber on the surface of a Ni-coated cotton yarn. The Ni-coated cotton yarn serves as conductive electrodes, and the nanofiber coating provides a dielectric layer. The three-dimensional elastic porous nanofiber structure of the dielectric layer, the fiber aggregate structure of the conductive electrode, and the helical structure of the elastic composite yarn play key roles in allowing the sensor unit of the electronic fabric to improve sensitivity, realize multiple-force sensitivities and realize stretchable and woven wearability. The sensor unit that can induce a large contact-area accumulation of the nanofiber dielectric layers under low external force exhibits excellent sensitivity (1.59 N−1, ＜0.3 N), a wide sensing range (0–5 N), a low detection limit (0.001 N), a short response time (＜50 ms), good cycling stability and repeatability, as well as high strain sensitivity over a wide range (0–100%). In addition, we demonstrate that the electronic fabric is suitable for voice recognition, noncontact airflow monitoring, finger and wrist muscle movements, and noncontact proximity of fingers. This flexible, elastically woven textile-based sensor demonstrates potential applications in wearable electronic devices and humanoid robots due to its superior performance. [ABSTRACT FROM AUTHOR]

Multi-nozzle air jet electrospinning was used to produce continuous viscose filament/polyvinylidenefluoride (PVDF) nanofiber hybrid yarns. The production of PVDF nanofibers using this method was based on the principle that the rupture of bubbles results in multiple jet flows. Nanofibers ejected from multiple nozzles were gathered and bundled by conjugate electrospinning and were then twisted on the surface of a filament yarn through the rotation of a metal funnel. The structures and properties of the hybrid yarn were characterized, and spinning mechanism of this novel method was analyzed. The experimental results obtained in this study showed that PVDF nanofibers were perfectly coated on the filament yarn surface with a good orientation and displayed uniform twist distribution with a twist angle of 24.3°, as well as PVDF nanofibers integrated with the core yarn well. After coating with twisted PVDF nanofibers, the mechanical properties of the yarn improved significantly. The stress and strain of the yarn at break increased from 19.39 MPa and 15.83% to 30.82 MPa and 19.81%, respectively. In addition, the hybrid yarn contact angle reached 150° after coating with the twisted PVDF nanofibers, indicating a transformation of the yarn from hydrophilic to hydrophobic. The nanofiber-coated hybrid yarn produced herein can possibly be used as a self-cleaning fabric. [ABSTRACT FROM AUTHOR]

Three different nanofiber yarns with various structures are first fabricated using a custom-made, coaxial, conjugate, electrospinning set-up. These yarns are then subjected to thermal stabilization and carbonization to obtain polyacrylonitrile-based carbon nanofiber yarns (PAN-based CNY), PAN/poly(methyl methacrylate)-based carbon nanofiber yarns (PAN/PMMA-based CNY), and C/Cu composite nanofiber yarns. The structures of the three CNYs are characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The electrical conductivity of the samples is measured using a four-point probe method. In the case of the PAN-based CNY, the fibers strongly adhere to each other and eventually fracture, making the individual fibers no longer distinguishable from each other. On the other hand, the PAN/PMMA-based CNY and C/Cu composite nanofiber yarns are composed of independent fibers that are well oriented. Moreover, for the C/Cu composite nanofiber yarn, a nanowire composed of Cu nanoparticles is observed along the central axis of these fibers. In addition, Cu nanoparticles uniformly adhere to the surfaces of these fibers. Compared to the PAN-based CNY, the electrical conductivity of the C/Cu composite nanofiber yarns is significantly higher. [ABSTRACT FROM AUTHOR]

Continuous polyacrylonitrile nanofiber yarns were fabricated by the homemade multiple conjugate electrospinning apparatus, and the principle of yarn spinning was studied. The effects of the applied voltage, flow rate, spinning distance, and funnel rotary speed on the diameter and mechanical properties of nanofiber yarn were analyzed. The diameter of the nanofibers decreased with increasing applied voltage and the flow rate ratio of the positive and negative needles ( FP/ FN), whereas the diameter of nanofibers increased with increasing overall flow rate and needle distance between the positive and negative. Subsequently, the diameter of the yarns increased first and then decreased with increasing applied voltage, FP/ FN, and needle distance. However, the diameters of the yarns increased dramatically and then remained stable with increasing overall flow rate. The nanofibers were stably aggregated and continuously bundled and then uniformly twisted into nanofiber yarns at an applied voltage of 20 kV, an overall flow rate of 6.4 mL/h, a needle distance of 18.5 cm, and an FP/ FN value of 5:3. With increasing funnel rotary speed, the diameters of the nanofibers and yarns decreased, whereas the twist angle of the nanofiber yarns gradually enlarged. Meanwhile, an increase in the twist angle brought about an improvement in the yarn mechanical properties. Nanofiber yarns that prepared showed diameters between 70 and 216 μm. Nanofiber yarns with a twist angle of 65° showed a tensile strength of 50.71 MPa and an elongation of 43.56% at break, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40137. [ABSTRACT FROM AUTHOR]

The development of highly sensitive, stretchable, and wearable electronic skin with multimodal mechanical‐sensing performance is of great research value for applications in health monitoring, and wearable electronic devices. In this work, a fabric‐like sensor with high flexibility and weavability that could detect the mechanical forces induced by pressure, strain, and flexion is designed. The fabric‐like sensor is woven by composite yarns (GCNF@ECYs) formed by winding graphene oxide‐doped polyacrylonitrile nanofiber yarns with in situ polymerized conductive polypyrrole on elastic yarns. The hierarchical structure of the fabric ranged from the macroscopic yarn to the submicron‐scale fibers to the nanometer‐scale particles as well as the wrapped structure constructed by winding conductive nanofiber yarn on elastic yarn. This offers more conductive pathways, larger deformation space, and multimodal mechanical‐sensing capabilities. The GCNF@ECY sensor unit has high sensitivity (the gauge factor was ≈68), wide pressure‐sensing range, excellent cycling stability, and good repeatability (over 10 000 cycles). The sensor can detect human respiration, facial expressions, pulse monitoring, and a full range of human motion. Moreover, the fabric sensor can be easily woven into textiles to produce electronic textiles with great potential in wearable human health monitoring electronics devices. In this work, a fabric‐like sensor with high flexibility and weavability that could detect the mechanical forces induced by pressure, strain, and flexion is designed. The sensor unit has high sensitivity (the gauge factor is ≈68), wide pressure‐sensing range, excellent cycling stability, and good repeatability (over 10 000 cycles). [ABSTRACT FROM AUTHOR]

One-dimensional, flexible yarn-shaped supercapacitors for woven cloth have the potential for use in different kinds of wearable devices. Nevertheless, the challenge that supercapacitors face is low energy density. In this paper, we present a low-cost and large-scale manufacturing method to construct a supercapacitor yarn with high power and high energy density. To construct the novel and flexible poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)–polyacrylonitrile (PDEOT: PSS-PAN)/Ni cotton (PNF/NiC) capacitor yarn, an electrospinning technique was initially used to wrap the polyacrylonitrile (PAN) nanofibers around the core Ni-coated yarn. The PEDOT: PSS–PAN nanofiber composite electrode was created using in situ deposition and H3PO4/PVA was used as a gel electrolyte. This electrode material has a yarn/nanofiber/PEDOT: PSS nanoparticle hierarchical structure, providing a high specific area and enhanced pseudocapacitance. The electrode demonstrated a high volumetric capacitance of 26.88 F·cm−3 (at 0.08 A·cm−3), an energy density of 9.56 mWh·cm−3, and a power density of 830 mW·cm−3. In addition, the PNF/NiC capacitor yarns are lightweight, highly flexible, resistant to bending fatigue, can be connected in series or parallel, and may be suitable for a variety of wearable electronic products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu 2 O@Cu 9 S 5 yolk-shell nanospheres were prepared by a facial wet chemical method. • This catalyst display enhanced electrocatalytic properties for H 2 O 2 reduction. • This catalyst based sensor exhibits excellent H 2 O 2 sensing performance. • Performance include low detection limit, outstanding sensitivity and selectivity. It is urgent to develop highly active catalysts toward hydrogen peroxide (H 2 O 2) sensor in many industrial and biological processes, which usually is limited by high cost of instrumentation requirements and low-accuracy detection at low level. Herein, Cu 2 O@Cu 9 S 5 yolk-shell nanospheres has been synthesized via a facial wet chemical method and applied as electrocatalyst for non-enzymatic H 2 O 2 sensor. These Cu 2 O@Cu 9 S 5 yolk-shell nanospheres with mean sizes of 230 nm consisting of Cu 2 O conductive core and Cu 9 S 5 shell show numerous advantageous characteristics of well-sustained structural integrity, the homogeneous particle size distribution and visible mesoporosity morphology. The significantly improved electrocatalytic activity by catalyzing H 2 O 2 of the Cu 2 O@Cu 9 S 5 yolk-shell nanospheres as a sensor has been obtained by comparing with those neat Cu 2 O nanospheres and Cu 9 S 5 hollow nanospheres. This noticeable property is largely due to the synergistic catalysis effect of the contribution of the Cu 2 O and Cu 9 S 5. Cu 2 O@Cu 9 S 5 yolk-shell nanospheres based non-enzymatic H 2 O 2 sensor displays the relatively wide linear range from 0.1 μM to 3.5 mM with a high sensitivity of 299.74 μA mM−1 cm−2 but low detection limit of 28.83 nM (S/N ≥ 3) for electrochemical detection of H 2 O 2 , which is potentially superior to other similar Cu 2 O-based sensors that has been reported in the literatures. Additionally, this sensor also demonstrates excellent selectivity of H 2 O 2 in the presence of various coactive interferences. This novel Cu 2 O@Cu 9 S 5 yolk-shell nanospheres electrocatalyst provides a broad application prospect for H 2 O 2 sensing. [ABSTRACT FROM AUTHOR]