Looking to Kirigami to Shape Modern Wireless Technology

Andrew Corselli

Inspired by the ancient Japanese art of kirigami, this MXene material antenna array was created by researchers at Drexel University and the University of British Columbia. (Image: Drexel University)

The future of wireless technology — from charging devices to boosting communication signals — relies on the antennas that transmit electromagnetic waves becoming increasingly versatile, durable and easy to manufacture. Researchers at Drexel University and the University of British Columbia believe kirigami, the ancient Japanese art of cutting and folding paper to create intricate three-dimensional designs, could provide a model for manufacturing the next generation of antennas.

Recently published in the journal Nature Communications, research from the Drexel-UBC team showed how kirigami — a variation of origami — can transform a single sheet of acetate coated with conductive MXene ink into a flexible 3D microwave antenna whose transmission frequency can be adjusted simply by pulling or squeezing to slightly shift its shape.

The proof of concept is significant, according to the researchers, because it represents a new way to quickly and cost-effectively manufacture an antenna by simply coating aqueous MXene ink onto a clear elastic polymer substrate material.

“For wireless technology to support advancements in fields like soft robotics and aerospace, antennas need to be designed for tunable performance and with ease of fabrication,” said Yury Gogotsi, Ph.D., Distinguished University and Bach Professor in Drexel’s College of Engineering, and a co-author of the research. “Kirigami is a natural model for a manufacturing process, due to the simplicity with which complex 3D forms can be created from a single 2D piece of material.”

Standard microwave antennas can be reconfigured either electronically or by altering their physical shape. However, adding the necessary circuitry to control an antenna electronically can increase its complexity, making the antenna bulkier, more vulnerable to malfunction and more expensive to manufacture. By contrast, the process demonstrated in this joint work leverages physical shape change and can create antennas in a variety of intricate shapes and forms. These antennas are flexible, lightweight, and durable, which are crucial factors for their survivability on movable robotics and aerospace components.

To create the test antennas, the researchers first coated a sheet of acetate with a special conductive ink, composed of a titanium carbide MXene, to create frequency-selective patterns. MXene ink is particularly useful in this application because its chemical composition allows it to adhere strongly to the substrate for a durable antenna and can be adjusted to reconfigure the transmission specifications of the antenna.

MXenes are a family of two-dimensional nanomaterials discovered by Drexel researchers in 2011 whose physical and electrochemical properties can be adjusted by slightly altering their chemical composition. MXenes have been widely used in the last decade for applications that require materials with precise physiochemical behavior, such as electromagnetic shielding, biofiltration, and energy storage. They have also been explored for telecommunications applications for many years due to their efficiency in transmitting radio waves and their ability to be adjusted to selectively block and allow transmission of electromagnetic waves.

Here is an exclusive Tech Briefs interview — edited for length and clarity — with Dr. Mohammad Zarifi, from UBC, and Lingyi Bi, Lead Author from Drexel.

Tech Briefs: What was the biggest technical challenge you faced while developing these tunable radio antennas?

Zarifi: The first and biggest problem was the difference in conductivity between the conventional metals, such as copper or aluminum, and the MXene that is fabricated in Dr. Gogotsi’s lab and by Lingyi. So, we needed to go back and redesign everything from a microwave and antenna perspective. Since most of our knowledge is based on those conventional metals, we needed to rethink how to design these structures for use with MXene.

Bi: We also want to mention the form factor. Traditional antennas are not configurable, meaning that once their form factor has been established, they can only read certain frequencies. But with our antenna, using MXene, we can have a configurable antenna that can change its frequency.

Zarifi: There are other methods for reconfigurable antennas and reconfigurable surfaces. But, I want to point out two things here. One is, this is not only an antenna; it is more like a reflecting surface. And the second thing is the method of fabrication. Since the way we would be able to fabricate these surfaces is much easier and more environmentally friendly, we can also reduce the cost and apply it to a large surface. So, imagine a big building is blocking an antenna signal from reaching certain points behind it. You could attach frequency selective surfaces to the building, in order to redirect electromagnetic signals to the areas not covered by the main antenna. The biggest thing we have demonstrated here is that with those cuts and with this specific material, we can make this surface reconfigurable. That means that we can change and realign the beam to the area that we want.

Tech Briefs: Can you just explain in simple terms how it works?

Zarifi: When electromagnetic waves hit a surface, some go through, some reflect back, and some disappear. However, if we properly engineer these surfaces, we can select what frequency passes, what frequency reflects, and what frequency disappears. Let's say for example, if we don't want an intrusion to happen in a certain area, we can block the signal.

Tech Briefs: Do you have any further research, work, etc. on the horizon?

Zarifi: Absolutely. Right now, there is another article being prepared for submission by other Ph.D. students and researchers. We are planning to develop it for different frequencies and different applications. One application is RFID tags for clothing. We are very familiar with them; when we are shopping, you see that some silver color tags remain on the clothing.

The problem with them is that making silver ink and adjusting it is very difficult. Also, they are not very environmentally friendly. So, what we are doing in the next phase is trying to replace the nylon base with paper so it can easily be disposed of. And then using MXene instead of silver nanoparticles or silver paste as conductors.

Also, some companies, especially space companies, have reached out to me to see if they can use this technology for space applications. So, we are looking to see if we can test this material and its microwave properties in low temperatures because when it goes through space, it will be faced with low temperatures and temperature variations.

Bi: I would add that I think, for additional study, one key area that hasn't been addressed by MXene, which is not an issue for our current study, is external connection. Our current study is with passive surfaces, so we have not needed to connect them to electronics.