From cockpits to operating theatres, pressure is part of the job for those working in high-stakes environments, but scientists may have found a way to monitor the mind before it’s pushed too far.

Researchers from the University of Texas at Austin have developed a wireless ‘e-tattoo’, which, when stuck to the forehead, decodes brainwaves to measure cognitive strain and help track the mental workload of people in critical roles.

According to its creators, the e-tattoo may help track mental fatigue in demanding jobs, such as surgery, air traffic control, or lorry driving, where a small miscalculation can have serious consequences.

Setting out to improve on the current method of mental workload assessment, which relies on the NASA Task Load Index, a lengthy and subjective survey that participants complete after performing tasks, the research team developed the e-tattoo to help find workers’ cognitive ‘Goldilocks’ zone, where they are neither overwhelmed nor bored. 

“Our brain capacity cannot keep up and can easily get overloaded,” said Professor Nanshu Lu, co-author of the study. “There is an optimal mental workload for optimal performance, which differs from person to person.”

Publishing their findings in Device, Lu and her colleagues said that the lightweight, flexible e-tattoo could not only detect when the brain is struggling, but could also predict mental strain by measuring brainwave activity.

Attached directly to the skin, the e-tattoo uses four EEG electrodes, each picking up signals from different parts of the brain, while around the eyes, sensors tracked every flicker and blink, with participants challenged to complete a memory task that became increasingly difficult.

The data revealed that as cognitive demand rose, so did theta and delta brainwave activity, while at the same time, alpha and beta waves declined – a pattern linked to mental exhaustion.

The researchers then trained a computer model to estimate mental workload based on signals from the e-tattoo, successfully distinguishing between different levels of mental workload. The results show that the device can potentially predict mental fatigue.

“We’ve long monitored workers’ physical health, tracking injuries and muscle strain,” said Professor Luis Sentis, another co-author of the study.

“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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With the e-tattoo consisting of a lightweight battery pack, graphite-based conductive material and paper-thin sensors that can stretch and conform seamlessly to the skin, the device will allow researchers to move away from bulky, wired EEG caps that often provide false signals due to movement.

Cost is another advantage. Traditional EEG equipment can exceed $15,000 (£11,000), while the e-tattoo’s chips and battery pack cost $200 (£148), and disposable sensors are about $20 (£15) each, which the team hopes will make the device more commercially viable.

“Being low cost makes the device accessible,” continued Sentis. “One of my wishes is to turn the e-tattoo into a product we can wear at home.”