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The non-permanent 'e-tattoo' attaches to the forehead and enables the detection of mental strain without the need for bulky headgear. It is hoped the technology could be used to watch for fatigue in air traffic controllers or truck drivers.
"Technology is developing faster than human evolution. Our brain capacity cannot keep up and can easily get overloaded," says Nanshu Lu, the study's co-author, from the University of Texas at Austin. “There is an optimal mental workload for optimal performance, which differs from person to person.”
The e-tattoo analyses electrical activity from the brain, as well as eye movement, but unlike traditional electroencephalography caps (EEGs), which are bulky and require dangling wires and conductive gel, the e-tattoo is wireless and comprised of paper-thin, sticker-like sensors that stretch and conform to the skin.
“What’s surprising is those caps, while having more sensors for different regions of the brain, never get a perfect signal because everyone’s head shape is different,” says Lu. “We measure participants’ facial features to manufacture personalised e-tattoos to ensure that the sensors are always in the right location and receiving signals.”
The researchers tested the e-tattoo by giving six people a memory challenge that increased in difficulty. As the task got harder, there were higher levels of activity in theta and delta brainwaves measured by the device. The researchers say the device could also predict mental fatigue as they trained a computer model to estimate mental workload based on signals.
Cost is another benefit: traditional EEG equipment can cost in excess of $15,000, while the e-tattoo's chip and battery pack are just $200, and the disposable sensors about $20 each. “Being low cost makes the device accessible,” says co-author Luis Sentis from UT Austin. “One of my wishes is to turn the e-tattoo into a product we can wear at home.”
Researchers are now working to combine the device with ink-based sensors that can work on hair, allowing for full head coverage and more comprehensive monitoring. “We’ve long monitored workers’ physical health, tracking injuries and muscle strain,” says Sentis. “Now we have the ability to monitor mental strain, which hasn’t been tracked. This could fundamentally change how organisations ensure the overall well-being of their workforce.”
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