There have been a few stretchable health monitoring device breakthroughs over the years that are designed to flex with the human body while in natural motion. They are akin to wearing a Band-Aid with integrated circuits that can garner information on heart rates, respiration, and even the amount of sweat that leaves the body during exercising. Now engineers from Stanford University were able to create a stretchable wearable sensor that detects physiological signals emanating from the skin and transmits the data over to a clip-on receiver.
The BodyNet technology was demonstrated by placing sensors to the wrist and abdomen of a test subject, which monitored their pulse and respiration rate by detecting how the skin stretched and contracted during each breath and heartbeat. The engineering team spent three years developing the sensors with the idea that they should be comfortable to wear, have no rigid circuits, and should be able to power themselves.
The engineers designed the BodyNet sticker using a variation of RFID technology that uses an internal antenna to harvest some the energy from a body-worn receiver, much in the same fashion as using an RFID card. That collected energy is used to power the sticker’s motion sensors, which then take readings and beam the data back to the receiver. The key to the sticker’s functionality is the stretchable antenna, which was fabricated by screen-printing metallic ink onto a rubber substrate.
Unfortunately, whenever the rubberized antenna is stretched, the signal becomes weak and unreadable. To get around that issue, the engineers made a new type of RFID platform that detunes the sensors, which increases the tolerance of strain-induced changes in the electronic properties resulting in a strong signal. The engineers state their BodyNet technology will initially be used to monitor patients with sleep disorders or heart conditions.