Textiles are materials made of natural or synthetic fibers. They typically are produced by spinning fibers into yarns and then weaving or knitting the yarns into fabrics. Electronic textiles, or e-textiles, are fabrics with electronic circuits, devices, and interconnections woven, knitted, sewn, or embroidered into them using conductive yarns. E-textiles do not have to be wearable; they can just as easily be incorporated into home or office furnishings, such as carpets and drapes, as well as other nonapparel applications. In any case, e-textiles are characteristically lightweight and must be flexible, stretchable, washable, and resistant to strain, bending, and pressure. See also: Electronics; Manufactured fiber; Natural fiber; Spinning (textiles); Stress and strain; Textile

Conductive yarns can be made by drawing metal wire (for example silver, stainless steel, or nickel) down to very small diameters, such that they are flexible enough to be woven. They also can be made by metallizing the surface of yarns, such as wool, cotton, polyester, polyurethane, and polyamide (nylon), using evaporative or vacuum physical vapor deposition processes. A common example is silver-coated nylon yarn. Metal fibers, such as stainless-steel fibers, can be blended with other fibers, such as polyurethane, and spun to make conductive yarn. Depending on the application, the conductive yarns may or may not require a coating with an insulating material. See also: Activated carbon; Cotton; Drawing of metal; Nickel; Physical vapor deposition; Polyamide resins; Polyester resins; Polyurethane resins; Silver; Stainless steel; Wool

At present, most e-textiles are passive circuits, such as conductors and resistors, with active components, such as transistors, diodes, batteries, and solar cells, connected to them. However, research in active woven components is progressing rapidly. For example, researchers at Drexel University have demonstrated supercapacitors—chargeable energy-storage devices similar to batteries—that were knitted out of cellulose yarns (such as cotton, linen, and bamboo) that contained embedded activated-carbon particles. See also: Bamboo; Circuit (electronics); Linen; Supercapacitors

One of the most prominent e-textile applications is as fabric sensors. Electrocardiogram (ECG), electromyography, and electroencephalography (EEG) textile electrodes can be knitted or woven into garments. Stretch (elastic) sensors based on silver-coated nylon yarn, for example, can measure heart rate, respiration, and blood pressure. These types of circuits have been incorporated into fitness apparel and can detect conditions in the body through changes in pressure, which is measured in terms of the degree of stretch in the fabric. Silver-coated yarn has also been used to embroider antennae onto garments to transfer radio signals from sensors. See also: Antenna (electromagnetism); Bioelectronics; Electrodiagnosis; Electroencephalography; Electromyography