Like skeletal muscles having a fibrous structure, conducting polymers can actuate upon electrical stimulation and can be shaped into fibers. Through textile assembly strategies of such fibers, complex actuating architectures are possible. However, state-of-the-art strategies using short pieces of yarn, which compel manual integration, are not fully taking advantage of textiles. To manufacture actuating textiles that best exploit textile properties like softness and pliability, and to enable production upscaling, a production of continuous, actuating fibers is presented here. These fibers are produced from commercial polyamide 6/6 filaments by first continuously dip-coating in a modified commercial poly(3,4−ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) dispersion before the electropolymerization of polypyrrole (PPy), where the fibers are withdrawn continuously through an electrolyte solution containing the pyrrole monomer. By employing a cyclic dip-coating with individual viscosity, drying temperature, and withdrawal speed for each layer, and by adjusting the tension, speed, and applied potential of the electropolymerization, their isotonic strain is enhanced threefold. Their specific tension, at 400 µN tex⁻¹, reaches slightly higher than human skeletal muscle fibers. Furthermore, these continuous actuating fibers produced on the meter are processable in an industrial knitting machine. This study anchors the development of textile muscle fibers for future textile muscles.

With the rise of ion-based devices using soft ionic conductors, ionotronics show the importance of matching electronic and biological interfaces. Since textiles are conformal, an essential property for matching interfaces, light-weight and comfortable, they present as an ideal candidate for a new generation of ionotronics, i-textiles. As fibers are the building blocks of textiles, ionically conductive fibers, named ionofibers, are needed. However, ionofibers are not yet demonstrated to fulfill the fabric manufacturing requirements such as mechanical robustness and upscaled production. Considering that ionogels are known to be conformal films with high ionic conductivity, ionofibers are produced from commercial core yarns with specifically designed ionogel precursor solution via a continuous dip-coating process. These ionofibers are to be regarded as composites, which keep the morphology and improve the mechanical properties from the core yarns while adding the (ionic) conductive function. They keep their conductivity also after their integration into conformal fabrics; thus, an upscaled production is a likely outlook. The findings offer promising perspectives for i-textiles with enhanced textile properties and in-air electrochemical applications.

Ionotronic textiles or i-textiles offer in-air electrochemical applications and sensing due to their ionic character, mimicking phenomena of organisms. To manufacture different i-textiles with unique functions and characteristics, it is necessary to have a range of ionically conductive textile fibers or ionofibers to choose from. However, their means of production are not sufficiently explored to provide knowledge that meets the fabric manufacturing needs. For a textile application, surface functionalization is usually explored as a convenient way to build upon an already known textile material. In contrast, bulk functionalization allows for superior production rate, versatility, and durability. Additionally, the use of the synergy between ionic liquids and carbon nanotubes is seldom explored. Therefore, in this study, melt spinning is investigated regarding the use of an ionic liquid (IL) initially without and ultimately with multiwalled carbon nanotubes (CNTs) for the tailoring of the electrical and mechanical properties of ionofibers. Based on thermoplastic polyurethane (TPU) elastomers, IL-containing pellets are prepared using 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIm OTf) at different weight ratios. About the melt-spun monofilaments, their extrusion temperatures, their morphology through scanning electron microscopy with energy-dispersive X-ray, their fiber conductivity through electrochemical impedance spectroscopy and cyclic voltammetry, and their tensile properties are investigated. An optimum of the ratios of IL and CNTs is observed for the melt-spinning process, which results in fiber conductivities within the range of 10^–2 μS cm dtex^–1. Compared to a monofilament melt-spun with no IL and a CNT weight ratio above percolation threshold, the fiber conductivity is twice higher due to its intricate segregated network. Thus, this industrial textile-compatible process offers an alternative within the development of ionotronic fabrics.