At the Ubicomp 2019 conference,University of Massachusetts Amherst graduate students Ali Kiaghadi and S. Zohreh Homayounfar debuted health-monitoring sleepwear they call "phyjamas."

The electronically active garments contain unobtrusive, portable devices for monitoring heart rate and respiratory rhythm during sleep.

The inventors designed a new fabric-based pressure sensor and combined that with a triboelectric sensor - one activated by a change in physical contact - to develop a distributed sensor suite that could be integrated into loose-fitting clothing like pajamas. They also developed data analytics to fuse signals from many points that took into account the quality of the signal coming in from each location.

Credit: UMass Amherst/Andrew lab

This combination allowed them to detect physiological signals across many different postures. They performed multiple user studies in both controlled and natural settings and showed that they can extract heartbeat peaks with high accuracy, breathing rate with less than one beat per minute error, and perfectly predict sleep posture.

"Such pressured regions of the textile are potential locations where we can measure ballistic movements caused by heartbeats and breathing," explains Professot Deepak Ganesan, "and these can be used to extract physiological variables."

The difficulty is that these signals can be individually unreliable, particularly in loose-fitting clothing, but signals from many sensors placed across different parts of the body can be intelligently combined to get a more accurate composite reading. Phyjamas solved this problem.

"We expect that these advances can be particularly useful for monitoring elderly patients, many of whom suffer from sleep disorders," says Professor Trisha Andrew. "Current generation wearables, like smartwatches, are not ideal for this population since elderly individuals often forget to consistently wear or are resistant to wearing additional devices, while sleepwear is already a normal part of their daily life. More than that, your watch can't tell you which position you sleep in, and whether your sleep posture is affecting your sleep quality; our Phyjama can."