When tracking a sleeping person's eye movements, you typically have to stick hard-wired electrodes onto their face. Soon, however, an unobtrusive flexible mask could do the job – while also measuring their heart rate.
Traditionally, a technique known as electrooculography is utilized for tracking nocturnal eye movements. It involves adhering pairs of electrodes to the skin either above and below or to either side of each of the patient's eyes.
As the eye moves up and down or from side to side, its cornea (front of eye) and retina (rear) correspondingly move closer to or farther away from each electrode. Because the electrical fields of the cornea and retina differ from one another, the electrodes are able to determine which way the eye is facing relative to them, by picking up on changes in the detected electrical signals.
The tracking of such movements can be an important part of sleep studies, as it allows clinicians to know when a patient is in the REM (rapid eye movement) sleep phase. Unfortunately, though, most people find it difficult to sleep with electrodes stuck on their sensitive facial skin, and with multiple wires running from their face to a computer.
That's where the experimental new Chesma mask comes in.
Developed by an international consortium led by the University of Massachusetts Amherst, it incorporates multiple built-in electrodes on its underside. These are made from a soft, conformable polymer hydrogel combined with conductive silver threads, and they simply press up against the skin as the mask is worn on the face.
The device additionally contains a single pressure sensor that sits against an artery, for monitoring the wearer's heart rate – another important factor in sleep studies.
Tests indicated that the electrodes are very durable, staying attached and functional after 15 laundry cycles. They're also not adversely affected by build-up from cosmetics or skin waste, and they last for nearly 40 hours without drying out – when they do dry out, they can be made soft and gel-like again simply by adding a few drops of water.
Currently, one charge of the device's battery is good for about eight hours of use. It is hoped that once the technology is developed further, however, that figure could climb to as much as three days. The final version could have other applications besides sleep analysis, such as tracking the direction of wearers' gaze while they're playing VR-based games.
A paper on the research was recently published in the journal Matter.
Sources: University of Massachusetts Amherst, Cell Press via EurekAlert
