Although it is possible to control devices using brain waves, doing so usually involves having electrodes and conductive gel applied to one's head. Now, however, scientists have developed a new-and-improved type of "dry" electrode – and it's been used to mind-control a robot.
One of the obvious problems with conductive gel is the fact that users are left with a bunch of goop on their head, which they have to wash off. Additionally, some people's skin may have an allergic reaction to the gel.
Dry electrodes which don't require gel do exist, but they tend to be flat and rigid. This means that they don't conform well to the rounded contours of the head, and they have difficulty making contact with the skin if hairs are in the way. As a result, they tend to not perform as well as "wet" electrodes.
In an effort to address those limitations, scientists from Australia's University of Technology Sydney set out to create dry electrodes which were much more flexible and sensitive than any that had come before.
The researchers started out with sheets of silicon carbide film, and etched tiny shapes such as squares, bars, dots and hexagons into their surface. A thin layer of the film that made up the negative space surrounding these shapes was then removed, leaving the shapes protruding up from a flexible substrate.
Next, a layer of electrically conductive graphene was deposited on the surface of each shape. Finally, the film was cut into small squares made up of grids of the 10-micrometer-thick shapes. These squares were the finished dry-yet-flexible electrodes.
An elastic headband containing eight of the electrodes was then placed on a volunteer's head in such a way that the electrodes were at the bottom back end of the skull, overtop of the visual cortex. When an augmented reality headset was subsequently used to present the person with various visual cues, the electrodes were able to determine which cue was being viewed, by detecting the accompanying unique pattern of electrical activity in the brain.
A linked computer was in turn able to match each of those patterns up to a predetermined command, which was successfully used to remotely control a quadruped robot. The electrodes incorporating the hexagonal shapes performed best, even when applied over hair. And while it was determined that wet electrodes still worked a little better, the scientists state that the research has paved the way for much better-performing dry electrodes.
The study is described in a paper that was recently published in the journal ACS Applied Nano Materials.
Source: American Chemical Society
