Researchers developed 3D-printed sensors that can record brain activity on earbuds

Researchers at the University of California San Diego have figured out a way to turn everyday earbuds into high-tech gadgets that can record electrical activity inside the brain. The 3D screen-printed, flexible sensors are not only able to detect electrophysiological activity coming from the brain but they can also harvest sweat. Yes, sweat.

More specifically, sweat lactate, which is an organic acid that the body produces during exercise and normal metabolic activity. Because the ear contains sweat glands and is anatomically adjacent to the brain, earbuds are an ideal tool to gather this kind of data.

You may be wondering why scientists are interested in collecting biometric info about brain activity at the intersection of human sweat. Together, EEG and sweat lactate data can be used to diagnose different types of seizures. There are more than 30 different types of recorded seizures, which are categorized differently according to the areas of the brain that are impacted during an event.

But even beyond diagnostics, these variables can be helpful if you want to get a better picture of personal performance during exercise. Additionally, these biometric data points can be used to monitor stress and focus levels.

And while in-ear sensing of biometric data is not a new innovation, the sensor technology is unique in that it can measure both brain activity and lactate. However, what’s more important is that the researchers believe, with more refinement and development, we will eventually see more wearables that use neuroimaging sensors like the one being made to collect health data on everyday devices. In a statement, UC San Diego bioengineering professor Gert Cauwenberghs said that, “Being able to measure the dynamics of both brain cognitive activity and body metabolic state in one in-ear integrated device,” can open up tremendous opportunities for everyday health monitoring.

Throughout the development of the sensor technology, the researchers had to grapple with some obstacles. They needed to make the sensors as small and thin as possible so that they could collect tiny sweat samples. They also had to integrate “components that can bend” to account for the irregular shape of the ear according to Ernesto De La Paz, a Ph.D. alumnus who co-authored the research.

One primary technical challenge was being able to fit the sensors in the ear, specifically in the tragus of the ear, which is an anatomically unique space situated in front of the ear canal that can vary from one individual to another. This led the researchers to create a “stamp-like stretchable sensor,” which can be easily tacked onto an earbud’s surface.

But in order to make sure that the sensors would actually have direct contact with the ear and accurately pick up readings, researchers opted for 3D printed, spring-loaded sensors that “hold contact but can adjust as earbuds move.” The biometric sensors also had to be covered with a hydrogel film that made sure they would amply collect sweat from a wearer.

Despite their capabilities and rosy future as a potential diagnostic aid, the 3D printed sensors really need a considerable amount of sweat in order to be useful for data analysis. But the researchers said down the line the sensors will be more precise, so hard workouts may not be necessary for meaningful sweat analysis.