We here at Medgadget regularly cover new body-worn monitoring devices, and, judging by the way things are going, there’s a lot more to come as sensors get smaller, more capable, and easier to manufacture. On top of that, flexible electronics are poised to permit continuous monitoring of vital signs using devices that stick to and conform to the body’s shape and movement. One missing component is a flexible antenna that would transmit sensor readings to a central device.

Researchers at North Carolina State University have developed just such an antenna that can take shape of the body as it flexes, but that easily returns to its starting shape when released. The antenna is made by pouring a liquid polymer over a pattern of nanowires layed down using a stencil. When the polymer dries, the new material can be bent while preserving the conductivity of the wires within. The new antenna can be integrated with flexible sensors for all-in-one stick-on health monitoring devices.

This patterned material forms the radiating element of a microstrip patch antenna. By manipulating the shape and dimensions of the radiating element, the researchers 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.

The researchers also learned that, while the antenna’s frequency does change as it is stretched (since that changes its dimensions), the frequency stays within a defined bandwidth. “This means it will still communicate effectively with remote equipment while being stretched,” Jacob J. Adams [co-author of the study] says. “In addition, it returns to its original shape and continues to work even after it has been significantly deformed, bent, twisted or rolled.” As the frequency changes almost linearly with the strain, the antenna can be used a wireless strain sensor as well.

source:NC State