Sprayable antennas turn surfaces into ultra-thin, transparent transmitters
If a device connects wirelessly to other things, chances are high that it has an antenna in it. But as crucial as these components are, the rigid metals they're made of can limit what devices they can be built into. To help with that, researchers at Drexel University have developed a new kind of antenna that can be sprayed onto just about any surface.
The antenna is made up of an incredibly thin, metallic material known as "MXene" (pronounced "Maxine"). This stuff is a two-dimensional form of titanium carbide that's highly conductive, which allows it to transmit and direct radio waves.
Previously, we have seen MXene put to work in experimental batteries that recharge in seconds. In this case, the Drexel team created a powdered form that can be dissolved in water to form an ink or paint. That can then be sprayed onto a surface, effectively turning it into a 2D antenna in whatever shape is needed.
"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," says Yury Gogotsi, lead researcher on 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."
The team tested the new MXene antennas and found that despite their incredible thinness, their performance is comparable to existing antennas. To make sure that wasn't simply a property of being two-dimensional, the researchers also compared them to other 2D antennas made of materials like graphene, silver ink and carbon nanotubes. The MXene antennas were apparently 50 times better at preserving radio wave transmission than graphene, and 300 times better than silver ink.
"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," says Babak Anasori, co-author of the study. "The thinnest antenna was as thin as 62 nanometers — about a thousand times thinner than a sheet 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."
In experimenting with just how thin they could make the antennas, the team found that they still worked well at a thickness of just a few tens of nanometers, which is so thin they're transparent. They performed their best when layered up to be 8 micrometers thick, where they hit 98 percent of the maximum performance they were calculated to be capable of.
These MXene antennas could help give connectivity to just about anything, including flexible or wearable electronics. Interestingly, it's not the first time we've heard of sprayable antennas – a few years ago a company called ChamTech claimed to have developed a sprayable system that could turn trees and buildings into antennas to boost mobile signals, but nothing seems to have come of the idea since.
The research was published in the journal Science Advances. The team demonstrates the sprayable antennas in the video below.
Source: Drexel University