A neural implant provides information about activity deep inside the brain while sitting on its surface. The implant is made up of a thin, transparent, and flexible polymer strip that is packed with a dense array of graphene electrodes. The technology, tested in transgenic mice, brings the researchers a step closer to building a minimally invasive brain-computer interface (BCI) that provides high-resolution data about deep neural activity by using recordings from the brain surface.

The implant is a thin, transparent and flexible polymer strip that conforms to the brain’s surface. The strip is embedded with a high-density array of tiny, circular graphene electrodes, each measuring 20 micrometers in diameter. Each electrode is connected by a micrometers-thin graphene wire to a circuit board.

In tests on transgenic mice, the implant enabled the researchers to capture high-resolution information about two types of neural activity — electrical activity and calcium activity — at the same time. When placed on the surface of the brain, the implant recorded electrical signals from neurons in the outer layers.

Transparency is one of the key features of this neural implant. An implant made using graphene is transparent, which provides a completely clear field of view for a microscope during imaging experiments. (Image credit: David Baillot/UC San Diego Jacobs School of Engineering)

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