In a nutshell: A new carbon-based coating improves the performance of carbon-fibre microelectrodes, enabling two-way communication with single brain cells.

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Neural interfaces are implantable devices used for communicating with the brain. By inserting electrodes into the brain, researchers can study how the brain works and develop new therapies for neurological diseases.

But current neural interfaces are limited in their design and application. Most implantable devices communicate with the brain in only one way: they either record or stimulate brain activity. And, because inserting electrodes into the brain can lead to inflammation and scarring, the devices have limited lifespans.

To solve both of these problems, Brain Function CoE researchers from the University of Melbourne, National Vision Research Institute and RMIT University have developed a new coating for implantable devices. The research was led by Wei Tong from Michael Ibbotson’s group.

The new coating is made from two-dimensional plates of carbon material, stacked vertically to create ‘nanowalls’. When these carbon-based nanowalls are deposited onto the surface of electrodes, they increase their overall surface area. This improves the electrodes’ electrochemical properties.

The new coating improved the performance of carbon-fibre microelectrodes. The coated electrodes successfully stimulated cells in retinal tissue. They also recorded activity from single cells in the brain with a high signal-to-noise ratio.

The researchers also showed that the new coating is flexible and does not peel or crack when the electrodes are bent. Coated electrodes are still ultrathin, so they create minimal damage to the brain during insertion. And because the nanowalls are made from a carbon material, the immune system does not treat them like a foreign substance. This reduces the likelihood of scarring, enabling long-term use of the coated electrodes.

Next steps:
The researchers plan to demonstrate the safety and function of the coated electrodes in rodents over extended periods, such as six months or more.

Hejazi, M. A., Tong, W., Stacey, A., Sun, S. H., Yunzab, M., Almasi, A., . . . Garrett, D. J. (2020). High fidelity bidirectional neural interfacing with carbon fiber microelectrodes coated with boron-doped carbon nanowalls: An acute study. Advanced Functional Materials, 2006101. doi: 10.1002/adfm.202006101

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