Spray-on antennas for flexible, connected devices

2 mins read

Installing an antenna could be as easy as applying some bug spray, say in Drexel's College of Engineering researchers.

The promise of wearables, functional fabrics, the IoT, and their "next-generation" technological cohort seems tantalisingly within reach. But, researchers in the field will tell you a prime reason for their delayed "arrival" is the problem of seamlessly integrating connection technology - namely, antennas - with shape-shifting and flexible "things."

With this latest development, the researchers believe they could overcome this issue. These invisibly thin antenna are made from a type of 2D metallic material called MXene that are said to 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 Professor Kapil Dandekar, PhD of Drexel. "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."

According to the team, the MXene titanium carbide can be dissolved in water to create an ink or paint. 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 nanometers were able to communicate efficiently," said Asia Sarycheva of Drexel. "By increasing the thickness up to 8 microns, the performance of MXene antenna achieved 98% of its predicted maximum value."

Preserving transmission quality in a form this thin is significant, the researchers say, because it would allow antennas to easily be embedded in a variety of objects and surfaces without adding additional weight or circuitry or requiring a certain level of rigidity.

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 aluminium, but are much thicker than MXene antennas.

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 50 times better than graphene and 300 times better than silver ink antennas in terms of preserving the quality of radio wave transmission, the researchers claim.

"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 Assistant Professor Babak Anasori of Drexel. "The thinnest antenna was as thin as 62nm and 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