Keeping an Eye on Fatigue

Missing a night of sleep can be more than just exhausting; it can impact your mood, cognitive function, and even your physical health. For those who do not have the luxury of missing a beat in their profession, like airline pilots and truck drivers, that loss of cognitive function, in particular, is troubling. When one wrong move can cost hundreds of people their lives, we cannot take any chances.

It is for this reason that certain professions have protocols for preventing accidents caused by sleep deprivation. One of the tools frequently employed is an assessment of each individual’s alertness. Unfortunately, while these assessments may be well-intentioned, they are not always especially useful. Many of them simply survey the workers, which can be an unreliable indicator of fatigue. More concrete results can be captured with an EEG, but that requires a trip to a lab, which is impractical for most situations.

A solution to this problem may soon be on the way. A new wearable device developed at the University of California, Los Angeles could give us a solid answer about one’s level of fatigue in a compact and portable package. Their soft magnetoelastic sensor attaches to the eyelid, and it can provide continuous, real-time measurements of the wearer’s fatigue level by tracking movements of the eye.

The idea behind the device is based on the observation that how we blink changes when we are tired. Blinks become slower, less frequent, and more irregular as fatigue builds. Capturing that information reliably, however, has never been easy. To make it possible, the team’s design uses a thin gold coil patterned onto a stretchable elastomer, which sits atop a magnetoelastic film filled with microscopic magnets. Each blink deforms the material slightly, altering its magnetic field in a way that can be converted into electrical signals.

The resulting sensor translates eyelid motion into clean, continuous data, without needing bulky equipment or invasive monitoring. Unlike many bioelectronic devices, it does not need batteries for operation and is fully waterproof, thanks to the magnetic sensing mechanism that is not hampered by sweat or humidity. These factors make it suitable for use outside the lab, so it is practical for workers on construction sites, behind the wheel, or anywhere else fatigue could compromise safety.

Looking ahead, this basic sensor design could find applications beyond fatigue monitoring. Similar devices could one day track pulse waves, respiration, or muscle movement, enabling a new generation of biomedical sensors and therapeutic tools. One might even envision future applications in haptic feedback systems, human-machine interfaces, or environmental monitoring.