Future of IoT may be skin-deep

A breakthrough by researchers at Drexel University in the US means that the next generation of internet of things devices may well not need bulky external antennas to communicate over wi-fi or Bluetooth.

Instead, the devices could simply be sprayed with a special conducting paint which will effectively make the device’s outer case the transmission/receive antenna.

The coating, comprising of a material belonging to a family of carbides and nitrites known as MXenes (pronounced “max-eens”), means that internet of things devices would only need a titanium carbide coating of a few tens of nanometres.

MXenes were discovered by the Drexel researchers in 2011 in the Department of Materials Science and Engineering, led by Yuri Gogotsi. MXenes can now be dissolved in water to create conductive paint.

Antennas only as thick as 8 µm possess low enough reflection coefficient (-65 dB) to be of practical value (the ratio of reflected, or lost signal to successful).

The antennas are at least as good as counterparts made from gold, copper or aluminum, the performance of which is limited by their “skin depth”. This is the minimum thickness of the material through which radio frequencies can flow.

“This is a first since 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 Gogotsi.

According to the team, MXene antennas are 200 times better than existing silver ink antennas in preserving the quality of radio transmissions.

“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 member of the research team.

“Unlike other nanomaterials’ fabrication methods, that require 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.”

Even graphene, the “miracle material” familiar to many, conducts radio frequencies quite poorly in comparison. Researchers have so far been successful in creating antennae on cellulose paper and PET sheets (polyethylene terephthalate).

Research like this opens the way for antennas to appear just about anywhere, in clothing (hospital gowns or scrubs), or even on human skin. Industrial applications may also present themselves where external antennas are not practical, such as in situations where an antenna would disrupt machinery’s functions.

Connectivity to and from IoT devices is one of the critical issues in any use case scenario of the technology, and by using existing standards like Bluetooth or wi-fi, costs of specialist deployments will be significantly lower.

The full paper appears in Science Advances.