This technology has the potential to track the mental workload of workers like air traffic controllers, surgeons, truck drivers – all jobs that depend on people to calculate properly.
“Technology is developing faster than human evolution. Our brain capacity cannot keep up and can easily get overloaded,” said Nanshu Lu, the study’s co-senior author from the Department of Aerospace Engineering and Engineering Mechanics at The University of Texas at Austin. “There is an optimal mental workload for optimal performance, which differs from person to person.”
Humans reportedly perform best in a cognitive Goldilocks zone; neither overwhelmed nor bored. Finding that balance is key to optimal performance. Current mental workload assessment relies on the NASA Task Load Index, a lengthy and subjective survey participants complete after performing tasks.
The e-tattoo suggests an objective alternative by analysing electrical activity from the brain and eye movement – also known as electroencephalography (EEG) and electrooculography (EOG). Unlike EEG caps that are bulky, with dangling wires and lathered with squishy gel, the wireless e-tattoo consists of a lightweight battery pack and paper-thin sensors.
These sensors feature wavy loops and coils, a design that enables them to stretch and conform easily to the skin for comfort and clear signals.
“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,” said 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 on six participants who completed a memory challenge that increased in difficulty. As the mental load increased, participants demonstrated higher activity in theta and delta brainwaves, signalling increased cognitive demand, while alpha and beta activity decreased, indicating mental fatigue. These results suggest the device is capable of detecting when the brain is struggling.
But the device didn’t stop at detection. It could also predict mental strain. To do so, a computer model was trained to estimate mental workload based on signals from the e-tattoo, distinguishing between different levels of mental workload. The results show that the device can potentially predict mental fatigue.
Cost is another advantage: traditional EEG equipment can exceed costs of $15,000, while the e-tattoo’s chips and battery pack costs $200, and the disposable sensors are about $20 each.
“Being low cost makes the device accessible,” said Luis Sentis, co-senior author from UT Austin. “One of my wishes is to turn the e-tattoo into a product we can wear at home.”
While the e-tattoo currently only works on hairless skin, the researchers are working to combine it with ink-based sensors that work on hair. This will allow for full head coverage and more comprehensive brain monitoring. As robots and new technology increasingly enter workplaces and homes, the team hopes this technology will enhance our understanding of human-machine interaction.
“We’ve long monitored workers’ physical health, tracking injuries and muscle strain,” concluded Sentis. “Now we have the ability to monitor mental strain, which hasn’t been tracked. This could fundamentally change how organisations ensure the overall wellbeing of their workforce.”
