Conductive textiles

This topic merits separate treatment due to the novelty of the technology and wide variety of studies thus far the applications are primarily passive (unswitchable) camouflage in the microwave and far-IR regions, and sensors. 

The most well-known and most advanced work to date in CP-based conductive textiles has been that of Kuhn and coworkers at the Milliken Research Corp., Spartanburg, SC, USA, a division of the Milliken textiles group [268, 269, 485, 883]. This work involves the in-situ, template-type chemical polymerization of CPs, primarily poly (pyrrole), onto individual textile fibers, yielding a continuous. 

In a more recent study [268] the Milliken group described their in-situ polymerization procedure in detail, and investigated in detail the effects of such factors as dopant type and level, substrate (fiber) type, degradation, and monomer concentration. They found that the nature of the fiber appeared to have little influence on the polymerization, with hydrophilic fibers such as rayon or cotton working as well as 

It is to be noted however that these textiles remain static, passive (unswitchable, non--dynamic) camouflage materials. Applications for such textiles have also been claimed in ESD/antistatic coatings for industrial belts, e.g. in coalmines, and personnel uniforms, e.g. for explosion-proofness. 

Wiersma et al. at DSM Research, Geleen, The Netherlands [284] described an interesting way of coating textile fibers with CP/polyurethane and CP/alkyd blends from aqueous colloidal dispersions made in a commercially available aqueous resin dispersions. The dispersions included a polyurethane-in-water dispersion (DSM Resins URAFLEX XP 401 UZ, 40% solids content). A variant of the template-type in-situ polymerization was used. After polymerization, the dispersed CP sol could be applied as a coating onto the textile fibers. CPs used included P(Py) and P(ANi). 

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Particle size, pm 3 (AgCLAD silver-coated, thick-wall spheres), 45-125 (Metalite, silver-coated, fight glass spheres), 50 to 300 mm (Bekinox VS for conductive textiles) Conduct-O-Fil glass spheres - 12-92, copper flakes - 10-150... 

Beki-Shield - steel fibers for EMI protection of plastics Bekitex - metal-containing yams for conductive textiles Composite Material L.L.C., Mamaroneck, NY, USA... 

Thus, the processability of conducting textiles using conventional composite techniques allows for new industrial developments (high-performance absorbing materials for missiles, aircraft and space industry and warships). 

As a conductive textile electrode, Shieldex , an Ag-coated polyamide yarn produced by Statex Produktions Vertriebs GmbH (Bremen, Germany) represented... 

Figure 4.18 Results of electrodeposition of sensitized ZnO on ELITEX conductive textiles, (a) Current density during electrodeposition at 70°C from a resting oxygen-saturated aqueous 0.1 M ZnCl2 solution with 50pM eosinY (squares averaged by the dashed line) compared to the current density observed at a planar substrate rotating at 500 rpm under otherwise identical conditions (solid line).

The upper and lower layers have several electric conductive textile paths (1 and 2), which are arranged in parallel. The conductive paths of the lower layer (2) are arranged in a rotation through 90° to the conductive paths of the upper layer (1). The two layers have to be separated as long as no movement has been detected. Therefore the foam layer (3) from a conventional mattress can be used. To realise an electrical contact between the conductive paths of the upper and lower layers the foam has to be prepared with holes (4). 

The interconnection between the conductive textiles and the electronic unit safeguards the reliability of the whole system. Hence, the textile arts needed to be prepared for contacting to the electrical units. For this purpose end sleeves for strands and lustre terminals were attached to the conductive yams. After having prepared the circuit board layout and the control system console, the lustre terminals were connected to the console. Figure 9.10 shows an overview of the budding of the control system. 

Meyer et al. (2006) developed a three-layer structure capacitance sensor consisting of two conductive textile layers sandwiching a compressible spacer material (foam or textile) for motion and muscle activity detection. As the body moves, pressure is applied to the capacitance sensor, more specifically onto the spacer layer, and capacitance changes accordingly. The sensors were shown to be able to detect arm movement when placed on the biceps and triceps. 

By using an aqueous chemical growth method, as described earlier, ZnO nanoneedles were grown on a commercially available conductive textile fabric (ArgenMesh ... 

Ko YH, Kim MS, Park W, Yu JS. Well-integrated ZnO nanorod arrays on conductive textiles by electrochemical synthesis and their physical properties. Nanoscale Res Lett 2013 8(l) l-8. 

Khan A, Hussain M, Nur O, Willander M. Mechanical and piezoelectric properties of zinc oxide nanorods grown on conductive textile fabric as an alternative substrate. J Phys D Appl Phys 2014 47(34) 345102. 

Many of the wires used in the current generation garments with embedded electronic circuitry are cumbersome and awkward. They are simply strapped to the outside of the garments, or carried on the body. This adds bulk and weight to the garment that makes them uncomfortable and impractical for daily use. To enable the integration of electronic circuitry into textiles, a need has arisen for the development of electrically conductive textile fibers and yarns. 

One of the most widely used approaches for fabricating electrically conductive textiles from intractable ICPs is to use an in situ approach to polymerize a submicron thick coating of an ICP onto an existing textile substrate. In this in situ polymerization technique, the fabric is immersed in a solution containing the ICP monomer, an oxidant, and the desired dopant anion. This process is industrially applicable because it can be performed using standard textile dyeing equipment using aqueous solutions for both aniline and pyrrole. 

Besides using an in situ polymerization of pyrrole to form an electrically conductive textile, other researchers have adopted a two-step process. The major advantage of the two-step process is that it can be easily adapted into a continuous process for industrial applications. However, the structure of the polypyrrole may be different to that obtained from the in situ polymerization process. Several variations to the a two-step process include first immersing the textile support in a solution containing the oxidant and desired dopant anion and then exposing the impregnated textile to either pyrrole vapor [87-89] or pyrrole dissolved in an aliphatic solvent [90] to initiate the polymerization reaction. Alternately, the textile support may be first exposed to pyrrole vapor and then immersed into an aqueous solution containing the oxidant and desired dopant anion [91]. 

The in situ polymerization of aniline to form an electrically conductive textile was also first reported by Kuhn and coworkers [78,79] in which the polyaniline was deposited onto a textile substrate from an aqueous solution containing aniline, ammonium persulfate, hydrochloric acid, and either the disodium salt of 2,6-naphthalenedisulfonic acid or 1,3-benzenedisulfonic acid. In these studies, the polymerization conditions were controlled in order to deposit the polyaniline layer only onto the textile support with no polymer precipitating in the bulk liquid phase. This was accomplished by using dilute solutions of aniline (0.03 M). A subsequent study by Tzou and Gregory [92] on the deposition of polyaniline to nylon-6 fibers was focused on investigating the reaction kinetics of the chemically oxidative polymerization of aniline... 

In contrast, the in situ polymerization approach for depositing an intractable ICP, such as polypyrrole, onto an existing textile substrate has still been the most effective approach for fabricating electrically conductive textiles from these intractable ICPs. This technique has been successfiilly converted from laboratory into commercial production for producing large quantities of these textiles using a relatively inexpensive aqueous-based process. 

Kuhn, H.H., and W.C. Kimbrell. 1989. Electrically conductive textile materials and method for making same. US Patent 4,803,096. 

Kuhn, H.H. 1997. Adsorption at the liquid/solid interface Conductive textiles based on polypyrrole. Text Chem Color 27 17. 

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