A team of researchers at Duke University have 3-D printed potent electromagnetic metamaterials, using an electrically conductive material compatible with a standard 3-D printer. The demonstration can revolutionize the rapid design and prototyping of radio frequency applications such as Bluetooth, Wi-Fi, wireless sensing and communications devices.
Metamaterials are synthetic materials composed of many individual, engineered devices called cells that together produce properties not found in nature. As an electromagnetic wave moves through the metamaterial, each engineered cell manipulates the wave in a specific way to dictate how the wave behaves as a whole. Metamaterials can be tailored to have un-natural properties such as bending light backwards, focusing electromagnetic waves onto multiple areas and perfectly absorbing specific wavelengths of light. But previous efforts have been constrained to 2-D circuit boards, limiting their effectiveness and abilities and making their fabrication difficult.
The Duke materials scientists and chemists have shown a way to bring electromagnetic metamaterials into the third dimension using common 3-D printers. The key to making 3-D printed electromagnetic metamaterials a reality was finding the right conductive material to run through a commercial 3-D printer which usually uses plastics that are typically terrible at conducting electricity.
While there are a few commercially available solutions that mix metals in with the plastics, none are conductive enough to create viable electromagnetic metamaterials. While metal 3-D printers do exist, they cost as much as $1 million and take up an entire room.
Benjamin Wiley, an associate professor of chemistry at Duke and Shengrong Ye, a postdoctoral researcher, have already created a 3-D printable material that is 100 times more conductive than anything currently on the market. Wiley and Ye started a company called Electrifi by Multi3D LLC, which sells this more conductive material. Though it is still not nearly as conductive as regular copper, it is conductive enough to create a 3-D printed electromagnetic metamaterial.
The team has shown that not only is Benjamin’s Electrifi conductive enough, it interacts with radio waves almost as strongly as traditional metamaterials made with pure copper. The small difference is easily made up for by the printed metamaterials’ 3-D geometry with the results showing that the 3-D printed metamaterial cubes interact with electromagnetic waves 14 times better than their 2-D counterparts.
By printing numerous cubes, each tailored to specifically interact with an electromagnetic wave in a certain way, and combining them like Lego building blocks, researchers can now begin to build new devices. For the devices to work, however, the electromagnetic waves must be roughly the same size as the individual blocks. While this rules out the visible spectrum, infrared and X-rays, it leaves open a wide design space in radio waves and microwaves.
They are now starting to get more aggressive with their metamaterial designs to see how much complexity they can build and how much that might improve performance. Many previous designs were too complicated to make in large samples. You could do it for a scientific paper once just to show it worked, but you would never want to do it again. According to them, this process could change how the radio frequency industry prototypes new devices in the same way that 3-D printer changed plastic-based designs.
This work was supported by a Multidisciplinary University Research Initiative grant from the Office of Naval Research.
