North Carolina State University Researchers Develop ‘Stretchable’ Antennas

I've reported on "stretchable" antennas before, but in that application their ability to stretch was used to tune them to different frequencies. Researchers at North Carolina State University have developed a "stretchable" antenna for use with wearable health monitoring devices.

The NCSU researchers created the antenna by using a stencil to apply silver nanowires in a specific pattern and then pouring a liquid polymer over the nanowires. When the polymer sets, it forms an elastic composite material with the nanowires embedded in it with the desired pattern, allowing the pattern to be used as the radiating element of a microstrip patch antenna. The shape and dimensions of the radiating element determine its resonant frequency.

By now, you’re probably wondering what happens to that resonant frequency when the antenna is stretched. Dr. Jacob Adams, an associate professor of electrical and computer engineering at NC State explains that while the resonant frequency does change, it stays within a defined bandwidth.

"This means it will still communicate effectively with remote equipment while being stretched. In addition, it returns to its original shape and continues to work even after it has been significantly deformed, bent, twisted or rolled," said Adams.

More details on the stretchable antenna are available in the North Carolina State University news release and in a paper published on-line in ACS Applied Materials & Interfaces, "Stretchable and Reversibly Deformable Radio Frequency Antennas Based on Silver Nanowires." Lead author of the paper is Lingnan Song, an undergraduate at Zhejiang University who worked on the project at NC State during an exchange program. Co-authors include Amanda Myers, a Ph.D. student at NC State; and Dr. Jacob Adams, an assistant professor of electrical and computer engineering at NC State.

The antennas developed by the researchers include a 3-GHz microstrip antenna and a 6-GHz 2-element patch array. While these aren't close to broadcast frequencies, I wonder if a modified design might not be used to receive UHF TV or perhaps even VHF FM or TV if the fabric was large enough. Use of the stretchable antenna for two-way communications over commercial wireless networks seems unlikely unless the absorbed RF power on the skin could be reduced below FCC exposure limits.

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. As vice president of Broadcast Technology for NBCUniversal Local, H. Douglas Lung leads NBC and Telemundo-owned stations’ RF and transmission affairs, including microwave, radars, satellite uplinks, and FCC technical filings. Beginning his career in 1976 at KSCI in Los Angeles, Lung has nearly 50 years of experience in broadcast television engineering. Beginning in 1985, he led the engineering department for what was to become the Telemundo network and station group, assisting in the design, construction and installation of the company’s broadcast and cable facilities. Other projects include work on the launch of Hawaii’s first UHF TV station, the rollout and testing of the ATSC mobile-handheld standard, and software development related to the incentive auction TV spectrum repack.
A longtime columnist for TV Technology, Doug is also a regular contributor to IEEE Broadcast Technology. He is the recipient of the 2023 NAB Television Engineering Award. He also received a Tech Leadership Award from TV Tech publisher Future plc in 2021 and is a member of the IEEE Broadcast Technology Society and the Society of Broadcast Engineers.