Robust Yarn Research Articles

Strong and Robust Electrochemical Artificial Muscles by Ionic-Liquid-in-Nanofiber-Sheathed Carbon Nanotube Yarns.

To address the lack of a suitable electrolyte that supports the stable operation of the electrochemical yarn muscles in air, an ionic-liquid-in-nanofibers sheathed carbon nanotube (CNT) yarn muscle is prepared. The nanofibers serve as a separator to avoid the short-circuiting of the yarns and a reservoir for ionic liquid. The ionic-liquid-in-nanofiber-sheathed yarn muscles are strong, providing an isometric stress of 10.8MPa (about 31 times the skeletal muscles). The yarn muscles are highly robust, which can reversibly contract stably at such conditions as being knotted, wide-range humidity (30 to 90 RH%) and temperature (25 to 70 °C), and long-term cycling and storage in air. By utilizing the accumulated isometric stress, the yarn muscles achieve a high contraction rate of 36.3% s-1 . The yarn muscles are tightly bundled to lift heavy weights and grasp objects. These unique features can make the strong and robust yarn muscles as a desirable actuation component for robotic devices.

Machine-Washable Conductive Silk Yarns with a Composite Coating of Ag Nanowires and PEDOT:PSS.

Electrically conducting fibers and yarns are critical components of future wearable electronic textile (e-textile) devices such as sensors, antennae, information processors, and energy harvesters. To achieve reliable wearable devices, the development of robust yarns with a high conductivity and excellent washability is urgently needed. In the present study, highly conductive and machine-washable silk yarns were developed utilizing a Ag nanowire and PEDOT:PSS composite coating. Ag nanowires were coated on the silk yarn via a dip-coating process followed by coating with the conjugated polymer:polyelectrolyte complex PEDOT:PSS. The PEDOT:PSS covered the Ag nanowire layers while electrostatically binding to the silk, which significantly improved the robustness of the yarn as compared with the Ag nanowire-coated reference yarns. The fabricated conductive silk yarns had an excellent bulk conductivity of up to ∼320 S/cm, which is largely retained even after several cycles of machine washing. To demonstrate that these yarns can be incorporated into e-textiles, the conductive yarns were used to construct an all-textile out-of-plane thermoelectric device and a Joule heating element in a woven heating fabric.

Robust yarn electrodes for microbatteries with high areal capacity

This work reports the design strategy of mechanically robust yarn electrodes having high areal capacity (ca. 14 mAh/cm2) as building blocks for microbatteries. Lithium iron phosphate (LiFePO4) was embedded into poly(acrylonitrile) nanofibers (NFs) via electrospinning. The obtained NFs were assembled into yarns via a yarning process, and were then thermally treated to produce carbon NF yarns. A hot-stretching process was used between the yarning and thermal treatment processes, improving the mechanical (tensile modulus of 1.03 GPa and strength of 38 MPa) and electrical (43.1 S/cm) properties of the yarn electrodes. The free-standing yarn electrodes with different mass loadings showed stable cycling performances with reasonable reversible capacity (ca. 112 mAh/g) up to 30 cycles. These mechanically robust and electrochemically excellent yarn electrodes could serve as building blocks for various structures in advanced microbatteries requiring high areal density.

Merge multiple carbon nanotube fibers into a robust yarn

Carbon nanotube (CNT) fibers are merged into a robust larger-diameter yarn by using an adhesion agent of polyethylenimine (PEI). As compared to poly(vinyl alcohol) and epoxy, PEI molecules can unite neighboring CNT fibers by constructing a strong inter-fiber adhesion, owing to their high mobility to soften the fiber surface. The merged yarn inherits fully the tensile strength and toughness from the single fiber, remains electrically conducting, and can be stably used up to 180 °C even in O2. It also exhibits high mechanical performances under various application conditions, such as bending, pressing, twisting, and rubbing.