Electrical stimulation can be used for the treatment of various nerve and muscle injuries as well as acute and chronic pain conditions. An electrical pulse is applied to a muscle or nerve to activate ...excitable tissue using internal or external electrodes with the aim of building muscle strength, artificially creating or supporting limb movement or reducing pain. Textile electrodes offer several advantages over conventionally used disposable surface electrodes: they are flexible and re-usable and they do not require hydrogels, thereby avoiding skin irritation and allergic reactions and enhancing user comfort. This article presents a literature review that assesses the state of research on textile electrode constructions. Based on the review, production approaches and designs are compared, methods for evaluating stimulation discomfort and pain are proposed and issues related to user compliance are discussed. The article concludes with suggestions for future work focused on investigating the impacts of textile-based electrode parameters on comfort, convenience and ease of use.
Commercially available yarns are promising precursor for artificial muscles for smart fabric‐based textile wearables. Electrochemically driven conductive polymer (CP) coated yarns have already shown ...their potential to be used in smart fabrics. Unfortunately, the practical application of these yarns is still hindered due to their slow ion exchange properties and low strain. Here, a method is demonstrated to morph poly‐3,4‐ethylenedioxythiophene:poly‐styrenesulfonate (PEDOT:PSS) coated multifilament textile yarns in highly twisted and coiled structures, providing >1% linear actuation in <1 s at a potential of +0.6 V. A potential window of +0.6 V and –1.2 V triggers the fully reversible actuation of a coiled yarn providing >1.62% strain. Compared to the untwisted, regular yarns, the twisted and coiled yarns produce >9× and >20× higher strain, respectively. The strain and speed are significantly higher than the maximum reported results from other electrochemically operated CP yarns. The yarn's actuation is explained by reversible oxidation/reduction reactions occurring at CPs. However, the helical opening/closing of the twisted or coiled yarns due to the torsional yarn untwisting/retwisting assists the rapid and large linear actuation. These PEDOT:PSS coated yarn actuators are of great interest to drive smart textile exoskeletons.
A method of morphing conductive polymer coated textile yarns in twisted and coiled structures is demonstrated to achieve rapid and substantial linear actuation. The strain and speed are significantly higher than the maximum reported results from other electrochemically operated conductive polymer incorporated yarns. These yarn actuators are of great interest to drive smart textile fabrics and potentially results in low‐cost wearables.
Textile-based stimulation electrodes are a fast-growing research area. With their advantages including flexibility, reusability and the possibility for integration into garments, textile electrodes ...open up new possibilities that are not yet feasible today, e.g. various self-administrated treatments and rehabilitation based on neuromuscular electrical stimulation (NMES) or transcutaneous electrical nerve stimulation (TENS). So far, most research has shown that textile-based stimulation electrodes perform more reliable when wetted with an electrolyte. However, there is no systematic investigation about which type and amount of electrolyte to use.
In this study, double-layered textile electrodes have been produced by machine knitting with a size of 3 × 3 cm2. The electrodes were wetted stepwise with a liquid amount from 5 µL up to 320 µL; four levels of sodium chloride (NaCl) concentrations, i.e. 0.9%, 1.5%, 5% and 35%, plus pure deionized water as a reference liquid were chosen. The study analyzed the behavior of the skin-electrode impedance when changing the moisture content and NaCl concentration. In addition, equivalent circuits were modelled for deeper insights into the mechanisms causing an impedance change.
Results showed that the impedance was greatly influenced by the liquid amount with amounts of 5 µL already significantly reducing the impedance compared to dry electrodes, caused by a substantial reduction in resistance. The reactance, on the other hand, was only partly influenced by the liquid amount showing a reduction upon higher liquid amounts only within a range of 5 – 40 µL. Further, a significant influence on the impedance by the presence of ions was found where the skin-electrode systems wetted with NaCl solution were showing generally lower impedances than systems wetted with deionized water. However, within this, no remarkable influence of the NaCl concentration could be observed. As the impedance was found to be very sensitive to the moisture content in the system, it is recommended to introduce standardizations for impedance testing of wet textile electrodes with precisely controlled electrolyte volumes and liquid migration properties to make independent studies of textile electrodes more comparable.
Display omitted
•Electrode-skin impedance greatly reduced when using higher liquid amounts.•Extremely sensitive; visible impedance differences already in microliter range.•General presence of NaCl ions significantly reduces impedance and actual salt concentration does not affect impedance.
Textile electrodes, also called textrodes, for biosignal monitoring as well as electrostimulation are central for the emerging research field of smart textiles. However, so far, only the general ...suitability of textrodes for those areas was investigated, while the influencing parameters on the contact impedance related to the electrode construction and external factors remain rather unknown. Therefore, in this work, six different knitted electrodes, applied both wet and dry, were compared regarding the influence of specific knitting construction parameters on the three-electrode contact impedance measured on a human forearm. Additionally, the influence of applying pressure was investigated in a two-electrode setup using a water-based agar dummy. Further, simulation of an equivalent circuit was used for quantitative evaluation. Indications were found that the preferred electrode construction to achieve the lowest contact impedance includes a square shaped electrode, knitted with a high yarn density and, in the case of dry electrodes, an uneven surface topography consisting of loops, while in wet condition a smooth surface is favorable. Wet electrodes are showing a greatly reduced contact impedance and are therefore to be preferred over dry ones; however, opportunities are seen for improving the electrode performance of dry electrodes by applying pressure to the system, thereby avoiding disadvantages of wet electrodes with fluid administration, drying-out of the electrolyte, and discomfort arising from a "wet feeling".
Conducting fibres and yarns promise to become an essential part of the next generation of wearable electronics that seamlessly integrate electronic function into one of the most versatile and most ...widely used form of materials: textiles. This review explores the many types of conducting fibres and yarns that can be realised with conjugated polymers and carbon materials, including carbon black, carbon nanotubes and graphene. We discuss how the interplay of materials properties and the chosen processing technique lead to fibres with a wide range of electrical and mechanical properties. Depending on the choice of conjugated polymer, carbon nanotube, graphene, polymer blend, or nanocomposite the electrical conductivity can vary from less than 10−3 to more than 103 S cm−1, accompanied by an increase in Young’s modulus from 10 s of MPa to 100 s of GPa. Further, we discuss how conducting fibres can be integrated into electronic textiles (e-textiles) through e.g. weaving and knitting. Then, we provide an overview of some of the envisaged functionalities, such as sensing, data processing and storage, as well as energy harvesting e.g. by using the piezoelectric, thermoelectric, triboelectric or photovoltaic effect. Finally, we critically discuss sustainability aspects such as the supply of materials, their toxicity, the embodied energy of fibre and textile production and recyclability, which currently are not adequately considered but must be taken into account to ready carbon based conducting fibres for truly practical e-textile applications.
Electronic textiles (E‐textiles) are made using various materials including carbon nanotubes, graphene, and graphene oxide. Among the materials here, e‐textiles are fabricated with reduced graphene ...oxide (rGO) coating on commercial textiles. rGO‐based yarns are prepared for e‐textiles by a simple dip coating method with subsequent non‐toxic reduction. To enhance the conductivity, the rGO yarns are coated with poly(3,4‐ethylene dioxythiophene): poly(styrenesulfonic acid) (PEDOT) followed by electrochemical polymerization of polypyrrole (PPy) as the electromechanically active layer, resulting in textile actuators. The rGO‐based yarn actuators are characterized in terms of both isotonic displacement and isometric developed forces, as well as electron microscopy and resistance measurements. Furthermore, it is demonstrated that both viscose rotor spun (VR) and viscose multifilament (VM) yarns can be used for yarn actuators. The resulting VM‐based yarn actuators exhibit high strain (0.58%) in NaDBS electrolytes. These conducting yarns can also be integrated into textiles and fabrics of various forms to create smart e‐textiles and wearable devices.
A simple graphene oxide, PEDOT:PSS and PPy coated textile‐based soft actuator is presented that shows good electrochemical strain and force. This opens a new perspective in the development of textile yarns with enhanced conductivity and/or actuation with possible applications in the field of smart textile materials.
Microplastics in the environment are a subject of intense research as they pose a potential threat to marine organisms. Plastic fibers from textiles have been indicated as a major source of this type ...of contaminant, entering the oceans via wastewater and diverse non-point sources. Their presence is also documented in terrestrial samples. In this study, the amount of microfibers shedding from synthetic textiles was measured for three materials (acrylic, nylon, polyester), knit using different gauges and techniques. All textiles were found to shed, but polyester fleece fabrics shed the greatest amounts, averaging 7360 fibers/m
−2
/L
−1
in one wash, compared with polyester fabrics which shed 87 fibers/m
−2
/L
−1
. We found that loose textile constructions shed more, as did worn fabrics, and high twist yarns are to be preferred for shed reduction. Since fiber from clothing is a potentially important source of microplastics, we suggest that smarter textile construction, prewashing and vacuum exhaustion at production sites, and use of more efficient filters in household washing machines could help mitigate this problem.
A need exists for artificial muscles that are silent, soft, and compliant, with performance characteristics similar to those of skeletal muscle, enabling natural interaction of assistive devices with ...humans. By combining one of humankind's oldest technologies, textile processing, with electroactive polymers, we demonstrate here the feasibility of wearable, soft artificial muscles made by weaving and knitting, with tunable force and strain. These textile actuators were produced from cellulose yarns assembled into fabrics and coated with conducting polymers using a metal-free deposition. To increase the output force, we assembled yarns in parallel by weaving. The force scaled linearly with the number of yarns in the woven fabric. To amplify the strain, we knitted a stretchable fabric, exhibiting a 53-fold increase in strain. In addition, the textile construction added mechanical stability to the actuators. Textile processing permits scalable and rational production of wearable artificial muscles, and enables novel ways to design assistive devices.
In this work, high‐performance fibers such as aramid (Twaron), polyamide (PA6), polyester (PET), and hybrid Twaron/PA6 fibers were transformed into electroactive fibers by coating them with ...conjugated polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT) through vapor phase polymerization (VPP) method. The VPP is considered as an efficient technique for depositing CPs on different substrates regardless of their lower solubility in various solvents. In this paper, PEDOT‐coated high‐performance fibers were prepared under already optimized reaction conditions, and then a comparison between electrical, thermal, and mechanical properties of different fibers, before and after coating, was made. The obtained coated fibers were characterized through scanning electron microscope (SEM), thermogravimetric analysis (TGA), 2‐probe electrical resistance measurement method, and tensile testing. It was revealed that at particular reaction conditions, all high performance textile substrates were successfully converted into electroactive fibers. The voltage‐current (V‐I) characteristics showed that PEDOT‐coated polyester fibers exhibited highest conductivity value among all other substrate fibers. The active PEDOT layers on high performance fibers could behave as an antistatic coating to minimize the risks associated with static charges at work places. Also, the obtained fibers have potential to be used as smart materials for various medical, sports, and military applications.
Smart textiles have been around for some decades. Even if interactivity is central to most definitions, the emphasis so far has been on the stimuli/input side, comparatively little has been reported ...on the responsive/output part. This study discusses the actuating, mechanical, output side in what could be called a second generation of smart textiles—this in contrast to a first generation of smart textiles devoted to sensorics. This mini review looks at recent progress within the area of soft actuators and what from there that is of relevance for smart textiles. It is found that typically still forces exerted are small, so are strains for many of the actuators types (such as electroactive polymers) that could be considered for textile integration. On the other side, it is argued that for many classes of soft actuators—and, in the extension, soft robotics—textiles could play an important role. The potential of weaving for stress and knitting for strain amplification is shown. Textile processing enables effective production, as is analyzed. Textile systems are made showing automatic actuation asked for in stand‐alone solutions. It is envisioned that soft exoskeletons could be an achievable goal for this second generation of smart textiles.
Textiles and textile processing have potential for soft actuation and soft robotics. Actuating mechanisms possible to transfer to textile are discussed. Here a textile actuator, “textuator” based on electroactive polymers is shown. Like natural mammal muscles, it consists of fibres in parallel, is electrically driven and works by contraction. Large area production is potentially possible.
PDF
