May 5, 2017 | By Benedict

Researchers at Duke University have used an electrically conductive material to 3D print potent electromagnetic metamaterials. The research could be used to improve Bluetooth, Wi-Fi, and wireless sensing devices.

3D printed metamaterial cells can be combined like Lego bricks to create functional structures

Metamaterials are materials engineered to have properties not found in nature. Uniquely, these properties are generally the result of the material’s engineered structure (which often consists of tiny repeating patterns) rather than what the metamaterials are made of.

When arranged in particular ways, metamaterials can be used for a wide range of applications, functioning as lenses, sound filters, and even earthquake defenses.

One interesting use of electromagnetic metamaterials is in radio frequency applications, including Bluetooth, Wi-Fi, and wireless sensing sensing devices. Excitingly, a group of Duke researchers has just found a way to create such metamaterials using an off-the-shelf 3D printer.

“There are a lot of complicated 3D metamaterial structures that people have imagined, designed, and made in small numbers to prove they could work,” said Steve Cummer, professor of electrical and computer engineering at Duke.

“The challenge in transitioning to these more complicated designs has been the manufacturing process. With the ability to do this on a common 3D printer, anyone can build and test a potential prototype in a matter of hours with relatively little cost.”

3D printed cubes interact with electromagnetic waves 14 times more strongly than 2D shapes

At first glance, making electromagnetic metamaterials using an FDM 3D printer would appear to be a thankless task: plastics aren’t conductive, so you generally need a much more expensive metal 3D printer (SLM, SLS, DMLS etc.) to fabricate something conductive.

Fortunately, making conductive materials—even ones that can be extruded using a regular 3D printer—is this group’s specialty.

“Our group is really good at making conductive materials,” said Benjamin Wiley, Duke associate professor of chemistry. “We saw this gap and realized there was a huge unexplored space to be filled and thought we had the experience and knowledge to give it a shot.”

With the help of Shengrong Ye, a postdoctoral researcher at Duke, Wiley has been able to develop a 3D printable material that is 100 times more conductive than anything currently on the market. The highly conductive 3D printing material is currently being sold under the brand name Electrifi by Multi3D LLC, a startup founded by Wiley and Ye. (Last year, the filament was used to create this terrifying 3D printed Terminator head, complete with LED eyes.)

Electrifi is great for a whole host of electrical applications, but the question remained: could it be turned into a metamaterial?

In a research paper that has been published in Applied Physics Letters, Cummer and doctoral student Abel Yangbo Xie have shown that Electrifi is 1) easily conductive enough, and 2) capable of interacting with radio waves almost as well as traditional pure copper metamaterials.

Experiments showed that 3D printing the metamaterials made a big difference, with 3D cubes interacting with electromagnetic waves 14 times better than their 2D counterparts.

Each cube was 3D printed to interact with an electromagnetic wave in a particular way. Then, by combining the cubes like Lego bricks, the researchers were able to create completely new electromagnetic devices.

Researchers used a Prusa 3D printer to create the metamaterial blocks

Interestingly, the devices only work if their blocks are roughly the size of the electromagnetic waves they are interacting with. This means that, while they can’t work with the visible spectrum, infrared, or X-rays, they are perfect for interacting with radio waves and microwaves.

“We're now starting to get more aggressive with our metamaterial designs to see how much complexity we can build and how much that might improve performance,” Cummer said.

“Many previous designs were complicated to make in large samples. You could do it for a scientific paper once just to show it worked, but you'd never want to do it again. This makes it a lot easier. Everything is on the table now.”

The researchers think the 3D printed metamaterials could change how the radio frequency industry prototypes new devices.

"When you can hand off your designs to other people or exactly copy what somebody else has done in a matter of hours, that really speeds up the design process,” Cummer added.

A Prusa i3 RepRap 3D printer was used to fabricate the electromagnetic metamaterials.

 

 

Posted in 3D Printing Materials

 

 

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