Researchers have developed a three-dimensionally patterned graphene-based dry sensor that can measure electrical activity in the brain without relying on conductive gels. Dry sensors are less irritating and less allergenic than traditional “wet” sensors used in electroencephalography (EEG) to diagnose neurological disorders or control external devices via brain-machine interfaces. Dry sensors, mounted on an elastic headband and used with the augmented reality headset, interpreted brain signals, allowing hands-free control of the robot. While not yet as effective as wet sensors, this development marks a move towards easy-to-implement, non-invasive brain-machine interfaces.

It sounds like something out of science fiction: put on a special electronic headband and control the robot with your mind. But the latest research published now ACS Applied Nanomaterials, took steps to make it a reality. By designing a special three-dimensionally patterned structure that doesn’t rely on sticky conductive gels, the team created “dry” sensors that can measure electrical activity in the brain, even between hairs, bumps, and curves of the head.

Doctors monitor the brain’s electrical signals using electroencephalography (EEG), in which special electrodes are implanted or placed on the head surface. EEG helps diagnose neurological disorders, but can also be incorporated into “brain-machine interfaces” that use brain waves to control an external device such as a prosthetic limb, robot, or even a video game.

Most non-invasive versions involve the use of “wet” sensors attached to the head with a sticky gel that can irritate the scalp and sometimes trigger allergic reactions. Alternatively, the researchers are developing “dry” sensors that don’t require a gel, but so far none have worked as well as the gold standard of the wet variety.

While nanomaterials such as graphene may be a viable option, their flat and often scaly structure makes them incompatible with the irregular curves of the human head, especially over long periods of time. That’s why Francesca Jacopi and her colleagues wanted to create a three-dimensional graphene sensor based on polycrystalline graphene that could precisely monitor brain activity without any stickiness.

The team created several 3D graphene-coated structures with different shapes and patterns, each about 10 µm thick. Among the shapes tested, the hexagonal pattern worked best on the curved, hairy surface of the occiput—the area at the base of the head where the brain’s visual cortex is located. The team placed eight of these sensors on an elastic band that held them behind their heads.

Paired with an augmented reality headset that displays visual cues, the electrodes can identify which cue is being displayed and then work with a computer to convert the signals into commands that control the quadrupedal robot’s movement – ​​completely hands-free. While the new electrodes haven’t yet performed as well as wet sensors, the researchers say the work is a first step towards developing reliable, easy-to-install dry sensors to help expand the applications of brain-machine interfaces.