This new Brain Computer Interface fits between the hairs on your head

Even though today we can pack Brain Machine Interfaces (BMI) into glasses , print them onto you, put them into your ear buds, and the equivalent of children’s decal stickers most BMI are still typically unwieldy, which makes using them on the move a non-starter. Now though a new neural interface small enough to be attached between the user’s hair follicles keeps working even when the user is in motion.

At present BMI are typically used as research devices designed to study neural activity or, occasionally, as a way for patients with severe paralysis to control wheelchairs, prosthetics, computers, or fleets of F-35 fighter jets. But there are hopes they could one day become a fast and intuitive way for people to interact with personal devices and post of social networks like Facebook through thoughts alone.

Invasive approaches that implant electrodes deep in the brain provide the highest fidelity connections, but regulators are unlikely to approve them for all but the most pressing medical problems in the near term.

Some researchers are focused on developing non-invasive technologies like Electroencephalography (EEG), which uses electrodes stuck to the outside of the head to pick up brain signals. But getting a good readout requires stable contact between the electrodes and scalp, which is tricky to maintain, particularly if the user is moving around during normal daily activities.

Now, researchers have developed a neural interface just 0.04 inches across that uses microneedles to painlessly attach to the wearer’s scalp for a highly stable connection. To demonstrate the device’s potential, the team used it to control an augmented reality video call. The interface worked for up to 12 hours after implantation as the wearer stood, walked, and ran.

“This advance provides a pathway for the practical and continuous use of BMI in everyday life, enhancing the integration of digital and physical environments,” the researchers write in a paper describing the device in the Proceedings of the National Academy of Sciences.

To create their device, the researchers first moulded resin into a tiny cross shape with five microscale spikes sticking out of the surface. They then coated these microneedles with a conductive polymer called PEDOT so they could pick up electrical signals from the brain.

Besides firmly attaching the sensor to the head, the needles also penetrate an outer layer of the scalp made up of dead skin cells that acts as an insulator. This allows the sensor to record directly from the epidermis, which the researchers say enables much better signal acquisition.

The researchers also attached a winding, snake-like copper wire to the sensor and connected it to the larger wires that carry the recorded signal away to be processed. This means that even if the larger wires are jostled as the subject moves, it doesn’t disturb the sensor. A module decodes the brain readings and then transmits them wirelessly to an external device.

To show off the device’s capabilities, they used it to control video calls conducted on a pair of XREAL augmented reality glasses. They relied on “steady-state visual evoked potentials,” in which the brain responds in a predictable way when the user looks at an image flickering at a specific frequency.

By placing different flickering graphics next to different buttons in the video call interface, the user could answer, reject, and end calls by simply looking at the relevant button. The system correctly detected their intention in real-time with an average accuracy of 96.4 percent as the user carried out a variety of movements. They also showed that the recording quality remained stable over 12 hours, while a gold-standard EEG electrode fell off over the same period.

The device was fabricated using a method that would allow mass production, the researchers say, and could also have applications as a wearable health monitor. If they can scale the approach up, an always-on connection between our brains and personal devices may not be so far away.