At the Université Laval in Quebec City, Canada, researchers have developed a respiration sensor built into a t-shirt that can be sampled by a nearby radio device. The idea is that patients in a hospital would wear a lightweight, comfortable shirt that doesn’t have any wires, while their breathing rate would be discreetly monitored in real-time. The sensor itself is simply a spiral antenna made out of multi-material fibres.
It’s embedded into the fabric of a common cotton t-shirt so that the expansion of the chest on every breath causes the antenna to bend slightly. This change in the geometry of the antenna affects its operational frequency, something that can be detected with a fairly simple radio device operating in the 2.45 GHz range, the antenna’s central frequency.
To evaluate the performance of the new system, the researchers had two males wear the t-shirt while sitting, standing, or lying down. During deep breathing, the sensor system was able to easily detect the antenna’s operational frequency changes as large as 120 MHz, and for shallow breathing the number was often as small as 4 MHz, yet still detectable.