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Conductive Fibers Weave Flexible Electronics [Chemical Engineering Progress](Chemical Engineering Progress Via Acquire Media NewsEdge) A new conductive fiber coating could enable wearable electronics without the wires. Potential applications include patient clothing that tracks heart rate, body temperature, and movement, as well as sensors for environmental monitoring. The new coating was created with atomic layer deposition (ALD) - a technique that sequentially exposes a surface to different chemicals to build up a thin film. The research team, led by North Carolina State Univ. assistant professor of textile engineering, chemistry and science Jesse Jur, used ALD to grow layers of electronic materials on various textiles, including woven cotton and nonwoven polypropylene. "We have been researching a wide range of coatings by atomic layer deposition, from metals to transparent conductors as well as semiconductors and insulators - the major components needed for microelectronic devices," Jur says. "We now have methods for growing these materials on a variety of textiles and synthetic nonwoven fiber materials, including polypropylene, nylon, and polyesters." The researchers formed zinc oxide (ZnO) films with thicknesses ranging between 20 nm and 100 nm using ALD at 1 1 50C on woven cotton substrates. When they compared the conductivity of the ZnO-coated cotton fibers to that of the ZnO-coated cotton paper and flat silicon substrates, they found that the effective conductivity of the ZnO films was about the same on woven cotton and paper substrates - demonstrating that ALD can produce similar conductivity values for different fiber materials. Electronic fabrics are not new. Many of these materials, however, consist of an electronic component sewn to a fabric or textile. Cambridge, MA-based mclO, for example, is developing stretchy electronic patches that can be incorporated into fitness apparel to measure everything from heart rate and blood pressure to joint injuries. The North Carolina State team takes this one step farther by actually turning the fibers themselves into electronic devices. "Our research team is attempting to blur the physical distinction between the fabric and the device by integrating these conductive layers directly into the textile, and this results in 'all-fiber' devices," Jur notes. The researchers do not speculate on when these electronic materials will be on store shelves, but say that their work is "advancing the technology much quicker toward commercialization." Their next step will be to combine the different layers (conductors, semiconductors and insulators) to form the actual microelectronic devices. They also plan to build more prototype materials to demonstrate how these textiles can be used, Jur says. A naturai fibrous material is shown here with (small swatch) and without the conductive coating. Adding electronic functionality to fabric systems is important for new applications in healthcare and environmental monitoring. Photo courtesy of Jesse Jur and Gregory Parsons, North Carolina State Univ. (c) 2011 American Institute of Chemical Engineers |