Graphene promises metal-free wearable electronics

Electronic textiles that communicate, sense, or power other devices promise a new era of smart wearable technology. But current e-textiles rely heavily on metals such as gold, silver, and copper, making disposal or recycling difficult. Using nanomaterials such as carbon in the form of graphene could offer an effective metal-free alternative, according to researchers from Isidoro Ibanez-Labianao and Akram Alomainy from Queen Mary University of London, M. Said Ergoktas and Coskun Kocabas from the University of Manchester, and Anne Toomey and Elif Ozden-Yenigun from the Royal College of Art [Ibanez-Labiano et al., Applied Materials Today (2020), 100727 https://doi.org/10.1016/j.apmt.2020.100727]. “[We] created a graphene-based communicating piece of cloth as a facilitator for the Internet of Things network and to provide a new understanding of the complexity of the human, natural, and material world,” says Ozden-Yenigun, who led the work. Wearable electronics have to continue functioning while being stretched, bent, and flexed repeatedly during use, as well as after repeated washing. To create such devices from graphene, the researchers used chemical vapor deposition (CVD) to grow multilayered graphene and transferred it onto a cellulose-based textile. A coplanar waveguide (CPW) design approach turns the thin layers of graphene into antennas, which can be used in wearable communication systems to talk to different devices elsewhere on the body or external systems. “The proposed antenna design is tuned to ensure the wearer’s comfort by eliminating the additional buffer layers and stiff components that are often used in radiating and ground layers,” explains Ozden-Yenigun. Creating planar graphene antennas with CPW avoids layer misalignment, is easy to integrate with textiles and fabrics, and is compatible with new fabrication techniques such as lamination and other add-on textile methods. The device itself can be tuned from the microwave to the terahertz range using an external field or chemical doping. Test devices show an operational bandwidth of 6 GHz, which is almost double the value previously reported for graphene devices, point out the researchers. CVD-grown graphene sheets also offer better surface coverage than screen-printed conductive textiles. “[Our] proposed methodology suggests a viable solution for a fully integrated textile-based communication interface that can replace current rigid, restrictive, and toxic approaches, [which are] causing a new type of waste, namely e-waste, of contaminated used textiles,” says Ozden-Yenigun. “[Graphene-based] body-centric communication [devices] could open up new revenues in sustainable and washable soft electronic components and systems.” The prototype devices appear to withstand repeated bending with only a slight change in performance and were put through washability tests. The main limitation now is the scale of multi-layer graphene synthesis, says Ozden-Yenigun. “There has been remarkable progress… in the last decade but we need a push in fabricating affordable off-the-shelf electrically conductive graphene products,” she says.