A method for spraying invisibly thin MXene antennas onto flexible substrates could lead to next-generation wireless devices including wearables, functional fabrics, and IoT devices.

In research published in Science Advances, a group from Drexel University’s College of Engineering in Philadelphia reported a method for spraying the antennas that are made from MXene, a type of two-dimensional, metallic material that is said to perform as well as those being used in mobile devices, wireless routers and portable transducers.

“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,” 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 researchers from the College’s Department of Materials Science and Engineering, report that the MXene titanium carbide can be dissolved in water to create an ink or paint. According to Drexel, the exceptional conductivity of the material enables it to transmit and direct radio waves, even when it’s applied in a very thin coating.

“We found that even transparent antennas with thicknesses of tens of nanometres 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 eight microns, the performance of MXene antenna achieved 98 per cent of its predicted maximum value.”

Preserving transmission quality in a form this thin would allow antennas to easily be embedded in numerous objects and surfaces without adding additional weight or circuitry or requiring a certain level of rigidity.

“This technology could enable the truly seamless integration of antennas with everyday objects which will be critical for the emerging Internet of Things,” Dandekar said. “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 made from gold, silver, copper and aluminium, but are much thicker than MXene antennas.

Drexel researchers discovered the family of MXene materials in 2011. The layered two-dimensional material, which is made by wet chemical processing, has shown potential in energy storage devices, electromagnetic shielding, water filtration, chemical sensing, structural reinforcement and gas separation.

In their paper, the Drexel researchers put the spray-on antennas up against a variety of antennas made from these new materials, including graphene, silver ink and carbon nanotubes. The MXene antennas were reportedly 50 times better than graphene and 300 times better than silver ink antennas in terms of preserving the quality of radio wave transmission.

“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, PhD, a research assistant professor in A.J. Drexel Nanomaterials Institute. “The thinnest antenna was as thin as 62nm and it was almost transparent. Unlike other nanomaterials fabrication methods, that require…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 will be looking at the best ways to apply it to a wide variety of surfaces from glass to yarn and skin.

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