"Graphene" and "wonder material" are a common pairing in science story headlines.

The first known truly two-dimensional material, graphene is a new form of carbon that has been generating consistent buzz since its discovery in 2004. And with potential applications for everything from water filtration systems to extremely efficient batteries, the excitement is far from unfounded.

While there is no shortage of wonder in regard to graphene's potential, the material so far lacks concrete commercial applications. However, products made with graphene are getting closer to hitting the market, and a low-cost 3D-printed antenna reported last week in the journal Applied Physics Letters could be among the first of such applications.

Printed with flexible graphene-based ink, the antenna's bendiness makes it an appealing option for wearables. It also avoids one of the key obstacles facing graphene: obtaining high-quality samples of the stuff in large quantities.

Senior author Zhirun Hu – whose co-authors included scientists Andre Geim and Kostya Novoselov, who won the 2010 Nobel Prize in Physics for discovering graphene – said in an interview that he estimates that graphene-based antennas made with this technique will likely be available within a year.

"Normally with graphene, you have less conductivity — so you cannot effectively radiate radio frequency signals," Hu said.

Radio frequency identification, or RFID, is a type of wireless data transmission already used for a variety of purposes, including in the microchips embedded in pets. Because such RFID tags can recieve power from remote RFID reader devices, they do not need batteries and can last a long time.

"This paper shows a step forward - it shows that you can use graphene to radiate RF signals effectively," Hu said.

Current RFID tags are made from metals such as aluminum and copper, which are expensive and difficult to manufacture. With interest in wearable technology on the rise, part of the appeal in these flexible printed graphene antennas is that they present an opportunity to incorporate RFID into a variety of wearable materials at low cost.

Prior to this work, all recipes for graphene ink included some sort of binder material, which essentially functions as graphene glue. This "glue" is very useful, according to Josep Miquel Jornet, because "we are at the point at which we can produce low-quality graphene at a large scale, but large-scale production of high-quality graphene - single layer, no impurities — that's very hard."

Jornet, an electrical engineer at SUNY Buffalo who was not involved in the work, went on to call the work by Hu and his colleagues "very nice." In other words, it is much easier, quicker and more cost effective to produce a bunch of small, lower-quality graphene flakes than it is to create larger, higher-quality pieces of graphene.

The researchers made graphene ink by smushing together a bunch of graphene nanoflakes, then compressing them, which Hu said allowed them "to increase the conductivity of the printed graphene without using a binder."

This is important, because binder materials present two notable problems that the researchers avoided with their binder-free technique. The first is that binder materials are insulators — so when you use them, it reduces the conductivity of the antenna, making them less efficient. The other problem is that when graphene ink contains a binder material, it has to be heated to very high temperatures — ruling out the option of printing on materials such as paper, plastic or many fabrics.

With the new binder-free method, it is possible to create antennas at temperatures of only 100 degrees Celsius, or about 212 degrees Fahrenheit, so they can be printed on a variety of different textiles.

A pliable, low-cost antenna that can be printed on similarly cheap and flexible materials like paper and plastic is well-suited to contribute to the Internet of Things, by making RFID truly ubiquitous. Hu said the next step is making printed wireless graphene sensors that "can detect, for instance, temperature change," noting that he and his colleagues already "are working on it."

Imagine a hospital where doctors could simply put a sticker on their patients that allows them to remotely monitor the temperature, blood pressure and other vital signs of patients in many different rooms. The low cost of wireless graphene sensors could open up an array of new possibilities for wearable technology.

"The point is that graphene is no longer just a scientific wonder," Novoselov said in a press release. "It will bring many new applications to our daily life very soon."

On a scientific time scale, graphene is already making incredibly quick progress for a new material. Graphene antennas represent a significant step toward turning scientific wonder into reality.

Photo: CORE-Materials | Flickr



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