A pair of standard earbuds can be turned into a device capable of recording brain activity and exercise levels.
They can measure the electrical activity of the brain as well as levels of lactate in the body with the addition of two flexible sensors screen-printed onto a stamp-like flexible surface, according to a new study.
The sensors communicate with the earbuds, which then wirelessly transmit the data gathered for visualization and further analysis, either on a smartphone or a laptop.
The data can be used for long-term health monitoring and to detect long-term neuro-degenerative conditions, say scientists.
They believe the sensors, developed by engineers at the University of California San Diego, are a lot less cumbersome than state-of-the-art devices currently used to sense the brain’s electrical activity and the body’s sweat secretions.
And the research team has shown that they can be used in the real world during exercise,.
While in-ear sensing of several physiological measures is not new, integrating sensing of brain and body signals in a single platform is.
The breakthrough was made possible by the combined expertise of biomedical, chemical, electrical, and nano-engineering.
Researchers say that data from an electroencephalogram (EEG), which measures electrical activity in the brain, and sweat lactate, an organic acid the body produces during exercise and normal metabolic activity, can be combined for several purposes.
For example, they can be used to diagnose different types of seizures. They can also be used for monitoring effort during physical exercise and monitoring levels of stress and focus.
The researchers validated the data collected during this proof-of-concept study against data obtained from commercially available dry-contact EEG headsets and lactate-containing blood samples.
The data the flexible sensors collected were just as effective.
The research team foresees a future, in which neuroimaging and health monitoring systems work with wearable sensors and mobile devices – such as phones, earbuds and watches – to track brain activity and levels of health-related metabolites throughout the day.
Professor Gert Cauwenberghs said: “Being able to measure the dynamics of both brain cognitive activity and body metabolic state in one in-ear integrated device that doesn’t intrude on the comfort and mobility of the user opens up tremendous opportunities for advancing health and wellness of people of all ages, anytime and anywhere.”
The team felt that the common wearing of earbuds translated to an “untapped” potential for gathering brain and body signals conveniently, both for wellness and health.
Professor Patrick Mercier said: “Earbuds have been around for decades, and in many ways were one of the first wearable devices on the market.
“This research takes important first steps to show that impactful data can be measured from the human body simply by augmenting the capabilities of earbuds that people already use on a daily basis.
“Since there are no major frictions to using this technology, we anticipate eventual wide scale adoption.”
The ear has sweat glands and is close to the brain, says Dr. Yuchen Xu, co-first author of the study.
He added: “It’s a natural entry point–people are used to wearing earbuds.”
Co-first author Dr. Ernesto De La Paz said: “One of the reasons why we were able to achieve this breakthrough was that we really thought about integration.
“We wanted to make the sensors as small as possible to collect tiny sweat samples. We also accounted for the irregular shape of the ear by integrating components that can bend.”
Dr. Xu said: “The primary technical challenge was not only fitting two sensors in the ear, which is a small space that varies from an individual to another, but also reliably acquiring signals from both EEG and lactate.
“We also had to accommodate for earbuds integration and reduce crosstalk.
“That’s when we landed on the idea of a stamp-like stretchable sensor, which is a simple addition to the earbud itself, but has all the necessary functions we needed and gave us enough freedom for our designs.”
To improve sweat collection, the team covered the electrochemical sensors with a see-through hydrogel film.
Dr. Xu said: “It’s sponge-like and hydrophilic. It acts as a mechanical cushion between skin and sensors and also helps collect sweat.”
Joseph Wang said: “This new and powerful in-ear multimodal wearable bioelectronic platform offers a rich source of real-time information on the health of the users, by recording simultaneously and dynamically physical and biochemical information.”
The team admitted that one of the devices’ limitations is that in order to gather enough lactate to meaningfully analyze data, subjects need to perform exercise or other physical activity that gets people to sweat.
In future work, the team aims to do away with that requirement.
Dr. Xu said: “The next step is also to integrate electronics into the sensor.”
The team’s ultimate aim is to transmit the processed data wirelessly to a computer or a smartphone.
They say in-ear sensors could also gather extra information – such as oxygen saturation levels and glucose levels – which could eventually lead to new treatments..
Cauwenberghs said. “Auditory neurofeedback coupling the measured brain signals with sound played by the device in the ear may enable potentially far-reaching new therapeutic advances for active remediation of debilitating neurological disorders, such as tinnitus for which currently no effective treatment is available.”
Dr. Sheng Xu added: “The ear canal has been relatively underexplored within the wearable technology community.
“This work demonstrates the potential of continuous sensing to capture valuable physical and chemical signals from the ear canal thereby paving the way for numerous exciting opportunities in the field of wearables.”
The work was described in the journal Nature Biomedical Engineering.
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