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Posted: Oct 29, 2013

Fabricating e-textiles with reduced graphene oxide

(Nanowerk Spotlight) The future of your clothes will be electronic. Not only will electronic devices be embedded on textile substrates, but an electronics device or system could become the fabric itself (see for instance: "Nanotechnology e-textiles for biomonitoring and wearable electronics"). These electronic textiles ('e-textiles') will have the revolutionary ability to sense, compute, store, emit, and move – think biomedical monitoring functions or new man-machine interfaces, not to mention game controllers – while leveraging an existing low-cost textile manufacturing infrastructure.
In a previous Nanowerk Spotlight ("Towards electronic textiles - putting conductive coatings on fibers") we described how one group of researchers used atomic layer deposition (ALD) to grow coatings of inorganic materials on the surface of textiles like woven cotton and nonwoven polypropylene.
In new work, a group of scientists from Korea have now reported novel method for the fabrication of conductive, flexible, and durable graphene textiles wrapped with reduced graphene oxide (RGO).
preparation of reduced graphene oxide nanoyarns
Schematic illustration of the three steps used to prepare the reduced graphene oxide (RGO) nanoyarns. (Reprinted with permission from Wiley-VCH Verlag)
As the team, led by Byung Hoon Kim, an Assistant Professor in the Department of Physics at Incheon National University, reports in Advanced Materials ("A Novel Method for Applying Reduced Graphene Oxide Directly to Electronic Textiles from Yarns to Fabrics"), these materials were fabricated by the electrostatic self-assembly of BSA molecules onto various textiles, including nylon-6 yarns, cotton yarns, polyester yarns, and nylon-6 fabrics, followed by a low-temperature chemical reduction.
"Our facile method opens a prompt pathway for the preparation of high-quality graphene e-textiles in the present textile industry," Kim tells Nanowerk. "Furthermore, their unique properties make these materials potentially useful in conducting wires and as functional fabrics in wearable electronics."
Kim explains that the key element of this novel technique is the use of bovine serum albumin (BSA) protein – an amphiphilic protein that can be attached to organic and inorganic materials through hydrophobic and hydrophilic interactions – which serves as a molecular glue for improving the adsorption of the graphene oxide onto any textiles regardless of materials and surface condition.
In their experiments, the researchers fabricated e-textile yarns and fabrics in three consecutive steps: 1) electrospun nylon-6 yarns were functionalized with BSA molecules via a simple dipping process which induced positive charges on the surface of the yarns; 2) a uniform coating of graphene oxide nanosheets was formed on the BSA-functionalized yarns via electrostatic self-assembly; and 3) conductive RGO yarns were obtained using a low-temperature vapor reduction method with hydroiodic acid as a reducing agent.
preparation of reduced graphene oxide nanoyarns
Image of a LED light integrated with a folded RGO nanofabric, which serves as an electrical interconnect. (Image: Prof. Byung Hoon Kim, Incheon National University)
Kim points out that this novel approach is applicable to various textiles that are presently used in the textile industry.
"Because invariance in the electrical conductivity of e-textiles under various conditions is an important property for wearable and flexible electronics, we measured the temperature-, bending-cycle-, and washing-number-dependent conductivity of the RGO nylon yarn," explains Kim . "In consideration of real-life weather, we measured the temperature-dependent conductivity from 220 K to 325 K. Although the conductivity of the yarn decreased as the temperature decreased, the variation was less than 9.0%, which indicates that the RGO nylon yarn is practical in real-life applications."
The researchers also conducted wearability test with regard to repeated bending of the fibers as well as washing tests with commercial detergents. In both cases, no significant variation in the electrical conductivity of the fabric was detected.
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