Researchers have developed a $220 temporary face tattoo that can track if a person's brain is working too hard, and whether they should be taking a break.
The University of Texas at Austin in the United States developed the e-tattoo, which decodes brainwaves to measure mental strain and tracks whether someone's brain capacity is overloading.
The e-tattoo is aimed at monitoring the brain waves of people in professions such as traffic controllers and truck drivers, where lapses in mental capacity can have serious consequences.
Researchers said their ultimate goal was to monitor work performance of people in high-risk roles, to determine whether they need to take a break to avoid mental fatigue.
The peer-reviewed study said there was a sweet spot for workers in these sorts of roles, where they were engaged and attentive, without being overloaded.
"On the contrary, performance may decline when mental workload is too low or too high," the study said.
"At low levels of mental workload, a person can become disengaged and make mistakes.
"At high levels, a person may become overwhelmed and lose control.
"Therefore, managing users' mental workload levels is of significant interest to designers of human in-the-loop systems to optimise performance."
How does it work?
Six people had the tattoo applied to them and were asked to complete two tasks on a computer designed to test their memories.
The tasks went for about two and a half hours to properly capture any fatigue.
The tasks would increase in difficulty.
Researchers said participants showed higher brain activity signalling increased cognitive demand.
They also observed when mental fatigue set in as brain activity decreased.
The e-tattoo captured real-time electroencephalogram (EEG) and electrooculography (EOG) signals while the tasks were completed, and researchers interpreted the results.
Electroencephalogram signals are electrical activity of the brain recorded through electrodes placed on the scalp, while electrooculography is a technique used to measure eye movements.
What did researchers find?
"We found that the model can successfully estimate the mental workload for all levels for all six subjects," the study said.
"Together, these results show that the EEG and EOG data collected by the e-tattoo system contained sufficient information for a reliable estimation of the mental workload evoked by the [tasks] in each of the six subjects."
The study found the e-tattoos could also predict mental strain, meaning it could potentially forewarn its subjects about approaching fatigue if necessary.
Researchers said while the e-tattoo was successful, it did have its limitations.
They found stable skin contact could impact its effectiveness, and sweating could reduce its adhesiveness.
As a result, researchers said they would need to test the e-tattoo outside of the laboratory to fully determine its effectiveness.
Why is this important?
Traditional EEG equipment costs about $15,000 to operate, and can be bulky and not allow for movement.
The e-tattoo, its chips, battery pack and sensors cost about $220.
Author Dr Luis Sentis said this was a crucial aspect of the study.
"Being low cost makes the device accessible," he said.
"One of my wishes is to turn the e-tattoo into a product we can wear at home."
Dr Sentis said the e-tattoo could potentially be revolutionary in workplaces where mental fatigue was a real risk to employees.
"We've long monitored workers' physical health, tracking injuries and muscle strain," he said.
"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."
University of Melbourne graduate researcher Jihoon Lim is working on a similar technology to monitor muscle fatigue.
He said accurately tracking fatigue in the workplace was a safety matter.
"Fatigue, especially mental fatigue, can impair critical cognitive functions such as concentration, decision-making, and reaction speed, increasing the risk of errors and workplace accidents," he said.
"Therefore, accurately tracking fatigue in real-time is essential to minimise these risks and maintain optimal productivity and safety standards."
Mr Lim said wearable tattoos were an important development for scientists.
"E-tattoos are particularly valuable because they offer continuous, non-invasive, and unobtrusive monitoring," he said.
"Traditional fatigue assessment methods often rely on subjective self-reporting or occasional clinical evaluations, which can be inconsistent or incomplete.
"In contrast, e-tattoos provide objective, real-time physiological data.
"This ease of use encourages regular wear, even during prolonged occupational activities, without causing discomfort or disrupting work routines."
Mr Lim said the technology would potentially help employees monitor their own wellbeing.
"Workers can proactively manage their fatigue, significantly improving workplace safety, health outcomes, and overall efficiency," he said.
"By enabling early detection of fatigue, e-tattoos allow timely interventions, including adjustments to work schedules, task rotations, and rest breaks, thus reducing workplace hazards and enhancing employee wellbeing and productivity."
The research was supported by the US Army Research Office and published in Cell Press.
