Stretchable antenna developed for wearable health monitoring
Even though many prototype sensors for wearable health systems have been developed there is still a clear need to develop antennas that can be easily incorporated into those systems to transmit data from the sensors, so that patients can be monitored or diagnosed, according to Dr. Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and senior author of a paper describing the work.
One of the key requirements of the project was to develop an antenna that could be stretched, rolled or twisted and always return to its original shape, because wearable systems can be subject to a variety of stresses as patients move around.
To create an appropriately resilient, effective antenna, the researchers used a stencil to apply silver nanowires in a specific pattern and then poured a liquid polymer over the nanowires. When the polymer sets, it forms an elastic composite material that has the nanowires embedded in the desired pattern.
The extremely flexible and resilient antennas contain silver nanowires and can be incorporated into wearable health monitoring devices. Credit: Amanda Myers, co-author.
This patterned material forms the radiating element of a microstrip patch antenna. By manipulating the shape and dimensions of the radiating element, one can control the frequency at which the antenna sends and receives signals. The radiating layer is then bonded to a "ground" layer, which is made of the same composite, except it has a continuous layer of silver nanowires embedded.
Further, it was demonstrated that while the antenna’s frequency does change as it is stretched (since that changes its dimensions), the frequency stays within a defined bandwidth. Consequently, the antenna will still communicate effectively with remote equipment while being stretched. When the antenna returns to its original shape it was found to still work even after it had been significantly deformed, bent, twisted or rolled.
In addition, since the frequency changes almost linearly with the strain, the antenna can be used a wireless strain sensor as well.
"Other researchers have developed stretchable sensors, using liquid metal, for example," Zhu says. "Our technique is relatively simple, can be integrated directly into the sensors themselves, and would be fairly easy to scale up."
The work on the new, stretchable antenna builds on previous research from Zhu’s lab to create elastic conductors and multifunctional sensors using silver nanowires.
The paper, "Stretchable and Reversibly Deformable Radio Frequency Antennas Based on Silver Nanowires," is published online in ACS Applied Materials & Interfaces. 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.
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
