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Antennas Made of Flexible Nanotube Films Could be Feasible Competitor for Copper in Wireless Applications

Scientists at Rice University’s Brown School of Engineering state that antennas made of carbon nanotube films can be just as efficient as copper for wireless applications. They are also more flexible, tougher, and can basically be painted onto devices.

Metal-free antennas made of thin, strong, flexible carbon nanotube films are as efficient as common copper antennas, according to a new study by Rice University researchers. (Photo by Jeff Fitlow)

The Rice lab of chemical and biomolecular engineer Matteo Pasquali examined antennas made of “shear-aligned” nanotube films. The experts learned that not only were the conductive films able to equal the performance of typically used copper films, they could also be formed thinner to better manage higher frequencies.

The results provided in Applied Physics Letters progress the lab’s earlier work on antennas made of carbon nanotube fibers.

The lab’s shear-aligned antennas were examined at the National Institute of Standards and Technology (NIST) facility in Boulder, Colorado, by lead author Amram Bengio, who performed the research and wrote the paper while earning his doctorate in Pasquali’s lab. Bengio has since set up a company to further advance the material.

At the target frequencies of 5, 10, and 14 gigahertz, the antennas can easily hold their own with their metal equivalents, he said. “We were going up to frequencies that aren’t even used in Wi-Fi and Bluetooth networks today, but will be used in the upcoming 5G generation of antennas,” he said.

Bengio noted other scientists have debated that nanotube-based antennas and their inherent properties have prevented them from compiling to the “classical relationship between radiation efficiency and frequency,” but the Rice experiments with more sophisticated films have proved them erroneous, allowing for the one-to-one comparisons.

To create the films, the Rice lab dissolved nanotubes, a majority of them single-walled and up to 8 µm long, in an acid-based solution. When spread onto a surface, the shear force formed triggers the nanotubes to self-align, an occurrence the Pasquali lab has used in other studies.

Bengio said that even though gas-phase deposition is extensively employed as a batch process for trace deposition of metals, the fluid-phase processing technique offers itself to more scalable, uninterrupted antenna manufacturing.

The test films were around the size of a glass slide, and ranging from 1 to 7 µm thick. The nanotubes are bound together by powerfully attractive van der Waals forces that give the material mechanical properties a lot better than those of copper.

The scientists said the new antennas could be appropriate for 5G networks as well as for wireless telemetry portals in downhole oil and gas exploration; for aircraft, particularly unmanned aerial vehicles, for which weight is a vital factor; and for future “internet of things” applications.

There are limits because of the physics of how an electromagnetic wave propagates through space. We’re not changing anything in that regard. What we are changing is the fact that the material from which all these antennas will be made is substantially lighter, stronger and more resistant to a wider variety of adverse environmental conditions than copper.

Amram Bengio, Chemical and Biomolecular Engineer and Study Lead Author, Brown School of Engineering, Rice University

“This is a great example of how collaboration with national labs greatly expands the reach of university groups,” Pasquali said. “We could never have done this work without the intellectual involvement and experimental capabilities of the NIST team.”

The paper’s co-authors of are Rice graduate student Lauren Taylor, research group manager Robert Headrick and alumni Michael King and Peiyu Chen; Damir Senic, Charles Little, John Ladbury, Christian Long, Christopher Holloway, Nathan Orloff and James Booth, all of NIST; and former Rice faculty member Aydin Babakhani, now an associate professor of electrical and computer engineering at UCLA. Pasquali is the A.J. Hartsook Professor of Chemical and Biomolecular Engineering, professor of chemistry and of materials science and nanoengineering. Bengio is the founder and chief operating officer of Wootz, L.L.C.

The research was supported by the Air Force Office of Scientific Research, the Department of Defense, and a National Defense Science and Engineering Graduate Fellowship.

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