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Tuesday, October 09, 2018

Sprayable, transparent antennas for the IoT

By Nick Flaherty www.flaherty.co.uk


Researchers at Drexel University’s College of Engineering have developed a technique for spraying invisibly thin antennas, made from a type of two-dimensional, metallic material called MXene, that perform as well as those being used in mobile devices, wireless routers and portable transducers.

“This is a very exciting finding because there is a lot of potential for this type of technology,” said Kapil Dandekar, PhD, a professor of Electrical and Computer Engineering in the College of Engineering, who directs the Drexel Wireless Systems Lab, and was a co-author of the research. “The ability to spray an antenna on a flexible substrate or make it optically transparent means that we could have a lot of new places to set up networks — there are new applications and new ways of collecting data that we can’t even imagine at the moment.”



Spray-applied MXene antennas could open the door for new applications in smart technology, wearables and IoT devices.

MXene titanium carbide can be dissolved in water to create an ink or paint and the high conductivity allows the printed structures to transmit and direct radio waves.

“We found that even transparent antennas with thicknesses of tens of nanometers were able to communicate efficiently,” said Asia Sarycheva, a doctoral candidate in the A.J. Drexel Nanomaterials Institute and Materials Science and Engineering Department. “By increasing the thickness up to 8 microns, the performance of MXene antenna achieved 98 percent of its predicted maximum value.”

“This technology could enable the truly seamless integration of antennas with everyday objects which will be critical for the emerging Internet of Things,” said Dandekar. “Researchers have done a lot of work with non-traditional materials trying to figure out where manufacturing technology meets system needs, but this technology could make it a lot easier to answer some of the difficult questions we’ve been working on for years.”

Initial testing of the sprayed antennas suggest that they can perform with the same range of quality as current antennas, which are made from familiar metals, like gold, silver, copper and aluminum, but are much thicker than MXene antennas. Making antennas smaller and lighter has long been a goal of materials scientists and electrical engineers, so this discovery is a major step in reducing their footprint as well as broadening their application.

“Current fabrication methods of metals cannot make antennas thin enough and applicable to any surface, in spite of decades of research and development to improve the performance of metal antennas,” said Yury Gogotsi, professor of Materials Science and Engineering in the College of Engineering, and Director of the A.J. Drexel Nanomaterials Institute, who initiated and led the project. “We were looking for two-dimensional nanomaterials, which have sheet thickness about hundred thousand times thinner than a human hair; just a few atoms across, and can self-assemble into conductive films upon deposition on any surface. Therefore, we selected MXene, which is a two-dimensional titanium carbide material, that is stronger than metals and is metallically conductive, as a candidate for ultra-thin antennas.”

Drexel researchers discovered the family of MXene materials in 2011 and have been gaining an understanding of their properties, and considering their possible applications, ever since. The layered two-dimensional material, which is made by wet chemical processing, has already shown potential in energy storage devices, electromagnetic shielding, water filtration, chemical sensing, structural reinforcement and gas separation.

“The MXene antenna not only outperformed the macro and micro world of metal antennas, we went beyond the performance of available nanomaterial antennas, while keeping the antenna thickness very low,” said Babak Anasori, a research assistant professor in A.J. Drexel Nanomaterials Institute. “The thinnest antenna was as thin as 62nm — about thousand times thinner than a sheep of paper — and it was almost transparent. Unlike other nanomaterials fabrication methods, that requires additives, called binders, and extra steps of heating to sinter the nanoparticles together, we made antennas in a single step by airbrush spraying our water-based MXene ink.”

The group initially tested the spray-on application of the antenna ink on a rough substrate — cellulose paper — and a smooth one — polyethylene terephthalate sheets — the next step for their work will be looking at the best ways to apply it to a wide variety of surfaces from glass to yarn and skin.

“Further research on using materials from the MXene family in wireless communication may enable fully transparent electronics and greatly improved wearable devices that will support the active lifestyles we are living,” said Anasori.


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