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A Brain-Computer Interface That Lasts for Weeks

Flexible EEG sensor stays stuck to your through showers, swims, and sleep

2 min read
A Brain-Computer Interface That Lasts for Weeks
Photo: John Rogers/University of Illinois

imgPhoto: John Rogers/University of Illinois

Brain signals can be read using soft, flexible, wearable electrodes that stick onto and near the ear like a temporary tattoo and can stay on for more than two weeks even during highly demanding activities such as exercise and swimming, researchers say.

The invention could be used for a persistent brain-computer interface (BCI) to help people operate prosthetics, computers, and other machines using only their minds, scientists add.

For more than 80 years, scientists have analyzed human brain activity non-invasively by recording electroencephalograms (EEGs). Conventionally, this involves electrodes stuck onto the head with conductive gel. The electrodes typically cannot stay mounted to the skin for more than a few days, which limits widespread use of EEGs for applications such as BCIs.

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Now materials scientist John Rogers at the University of Illinois at Urbana-Champaign and his colleagues have developed a wearable device that can help record EEGs uninterrupted for more than 14 days. Moreover, their invention survived despite showering, bathing, and sleeping. And it did so without irritating the skin. The two weeks might be "a rough upper limit, defined by the timescale for natural exfoliation of skin cells," Rogers says. 

The device consists of a soft, foldable collection of gold electrodes only 300 nanometers thick and 30 micrometers wide mounted on a soft plastic film. This assemblage stays stuck to the body using electric forces known as van der Waals interactions—the same forces that help geckoes cling cling to walls.

The electrodes are flexible enough to mold onto the ear and the mastoid process behind the ear. The researchers mounted the device onto three volunteers using tweezers. Spray-on bandage was used once twice a day to help the electrodes survive normal daily activities.

The electrodes on the mastoid process recorded brain activity while those on the ear were used as a ground wire. The electrodes were connected to a stretchable wire that could plug into monitoring devices. "Most of the experiments used devices mounted on just one side, but dual sides is certainly possible," Rogers says.

The device helped record brain signals well enough for the volunteers to operate a text-speller by thought, albeit at a slow rate of 2.3 to 2.5 letters per minute.

According to Rogers, this research: 

...could enable a persistent BCI that one could imagine might help disabled people, for whom mind control is an attractive option for operating prosthetics… It could also be useful for monitoring cognitive states—for instance, to see if people are paying attention while they're driving a truck, flying an airplane, or operating complex machinery. It could also help monitor patterns of sleep to better understand sleep disorders such as sleep apnea, or for monitoring brain function during learning.

The scientists hope to improve the speed at which people can use this device to communicate mentally, which could expand its use into commercial wearable electronics. They also plan to explore devices that can operate wirelessly, Rogers says. The researchers detailed their findings online March 16 in the journal Proceedings of the National Academy of Sciences.

The Conversation (0)

This Implant Turns Brain Waves Into Words

A brain-computer interface deciphers commands intended for the vocal tract

10 min read
A man using an interface, looking at a screen with words on it.

A paralyzed man who hasn’t spoken in 15 years uses a brain-computer interface that decodes his intended speech, one word at a time.

University of California, San Francisco
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A computer screen shows the question “Would you like some water?” Underneath, three dots blink, followed by words that appear, one at a time: “No I am not thirsty.”

It was brain activity that made those words materialize—the brain of a man who has not spoken for more than 15 years, ever since a stroke damaged the connection between his brain and the rest of his body, leaving him mostly paralyzed. He has used many other technologies to communicate; most recently, he used a pointer attached to his baseball cap to tap out words on a touchscreen, a method that was effective but slow. He volunteered for my research group’s clinical trial at the University of California, San Francisco in hopes of pioneering a faster method. So far, he has used the brain-to-text system only during research sessions, but he wants to help develop the technology into something that people like himself could use in their everyday lives.

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