Researchers at North Carolina State University, Raleigh, say that they have developed a new, stretchable antenna that can be incorporated into wearable technologies, such as health monitoring devices.
While many researchers have developed prototype sensors for wearable health systems, antennas that can be easily incorporated into those systems to transmit data from the sensors lagged behind. The team focused on developing an antenna that could be stretched, rolled, or twisted and easily return to its original shape, because wearable systems subjected to a variety of stresses as patients move around.
To create an appropriately resilient, effective antenna, they 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.
This patterned material forms the radiating element of a microstrip patch antenna, they explained. By manipulating the shape and dimensions of the radiating element, they said that they can control the frequency at which the antenna sends and receives signals. The radiating layer is then bonded to a “ground” layer made of the same composite, except that it has a continuous layer of silver nanowires embedded.
The researchers discovered that, while the antenna’s frequency does change as it is stretched due to its dimensions changing, the frequency stays within a defined bandwidth. This allows them to still communicate effectively with remote equipment while being stretched. As the frequency changes almost linearly with the strain, the antenna can be used a wireless strain sensor as well.