So far, there is very little true e-textile in production - that is, textiles with electronic and/or electric functionality based on weavable e-fibers. They form part of the broader category called textile electronics mainly involving no use of e-fibers. These more traditional forms are primarily used for such things as sensing (for health and fitness monitoring), warming (in outdoor wear), displays and lighting (including illuminating t-shirts and party fashions) and control (such as sleeve controls for your personal electronics and woven rollable keyboards). Then there is logistics, notably with stitched RFID labels. That will later include active RFID where there is a battery in the label or insert for real-time location, mesh networking and so on. These batteries will have energy harvesting in future.
Beyond clothing, the technology is being integrated into car and train seats. For example, EnOcean energy harvesters are used to monitor occupancy of seats in trains so that operators can judge when to add or remove carriages. The sensors are powered by the act of someone sitting on the seat. Nearly all of these current applications involve discrete devices distributed through or across the textile and many of these may be replaced by true e-textiles before the end of the coming decade. Reasons for that include lighter weight, better comfort and appearance and eventually lower cost and better functionality even making it attractive to the famous designer brands. At the other extreme, eventually some electronic functionality may be included "free" in volume runs of apparel whether it will be used or not, rather like the barcode today.
Adidas, with some of the largest sales of textile electronics in the world, including their fitness monitoring sports bra, sees some of the challenges and opportunities as:
• Low power electronics - Micro to milliwatts for wearable monitoring systems; several watts for heating system.
• In 2014, Kim Scheffler, Wearables Development Manager, Adidas Wearable Sports Electronics (aWSE) said, "Fully integrating electronics into textiles is limited by battery technology today". Part of this is improving duration of operation before the battery needs replacing or recharging, the trend being to rechargeable batteries.
• Sustainable power - environmentally friendly.
• "Lifetime" power - 6-18 months, 100 washes/wears.
• Trend towards body distributed networks - don't want multiple battery cells.
• Energy harvesting options - Thermoelectric; body/environmental differences. Piezoelectric; foot, elbow, knee, hip or body twisting motion. Also intelligent energy storage and power management.
Currently, the main materials employed in textile electronics include conductive inks, metal wires, plated synthetic fibers and filaments, printed or impregnated fabrics, electronic and electrical circuits in heat-sealed or stitched patches and labels and conductive polymers. An increase in effort in the last few years should speed commercialisation largely taking place near the end of the coming decade. However, if the benefits necessary for a given application are achieved satisfactorily by earlier products such as iron-on electronic patches on textiles or wearable devices then active fibers may not be introduced for those functions, particularly if they prove to be more challenging or more expensive. There is nothing inevitable about active fibers always being the end game. That said, a 2014 IDTechEx survey of 550 developers and manufacturers of wearable electronics in its report, Wearable Technology 2014-2024: Technologies, Markets, Forecasts found that most of their planned products are being made for places on the human body where e-textiles could provide advantages when they are available and affordable. Of course, e-textiles will potentially be used way beyond apparel, with furnishings, medical patches and bandages being examples of the wider potential market.
In the research for the new IDTechEx report, E-Textiles: Electronic Textiles 2014-2024, IDTechEx has found that the interest in weavable e-fibers extends to ones that are coated and ones that are inherently electric or electronic in functionality. Most work is aimed at making them harvest light and some of these photovoltaic developments seek to put energy storage on the same fiber. Other programs provide fibers that sense, have memory and even have two other functions on one fiber. Stretchable electronic and electrical fibers have been demonstrated and fibers constituting transistors, new forms of energy harvesting and more but progress to market is seen mostly with photovoltaic and better conductive fibers. There is even work on weaving fibers optics, carbon nanotubes and nanorods not intended for that purpose. Of course, basic weavable conductive fibers have been on the market for over a decade already.
IDTechEx concludes that the repertoire of different fiber-based components is inadequate to make much as yet but within the decade that will change. Weaving, knitting, knotting, embroidering and other localised stitching of these fibers has been demonstrated but the closely related technology of fibers trapping tiny microchips, LEDs and other conventional components into circuits completed by weavable conductive fiber may succeed commercially relatively soon. The report covers these and looks at timelines and approximate market size for the true e-textiles, recognising that it is too early to be very precise. A market of over US$1 billion awaits by the end of the decade and in twenty years that could be tens of billions of dollars. Many examples of projects are given, most being in universities and start-ups.