News Feature | April 24, 2017

Smaller, Gentler Brain Electrodes Worth Their Weight In Gold…And Graphene

By Suzanne Hodsden

Image courtesy of Daegu Gyeongbuk Institute of Science & Technology (S. Korea)

Scientists in South Korea are mining the biomedical potential of both gold and graphene to design a more flexible brain-machine interface (BMI) that can transmit clearer signals while causing minimal damage to brain tissue, said researchers. The platform could be used to record brain activity or to transmit stimulation treatments for neurological conditions like Parkinson’s and epilepsy.

Research in BMI technology is rapidly expanding and exploring a wide variety of applications from mind-controlled prosthetics to vision simulation in the blind. The main challenge of neural electrodes is creating circuitry that is strong enough to transmit signaling without breaking down, yet soft and flexible enough to be implanted in the brain without triggering an immune response. Advances in materials research have allowed scientists to design electrodes feasible for brain implants.

With graphene — a highly flexible, yet stable substance that effectively conducts both heat and electricity — scientists have found a material that ticks all the boxes of biocompatibility and long-term strength. The potential of graphene research is considered so high that the E.U. recently invested over €1.08 billion in its further development. Last month, a consortium of European researchers funded by that initiative introduced a graphene-based neural probe, commenting that the material demonstrated “excellent noise to signal ratio.”

A team of scientists from the Daegu Gyeonbuk Institute of Science and Technology in South Korea has paired the flexibility of graphene with gold, also known as an excellent conductor. Their proposed technology joins a thin gold base with zinc oxide nanowires, which are coated with gold and a conductive polymer. The combination of materials maximizes surface area, conductive properties, and strength while retaining the flexibility required by a BMI platform.

Because many tiny wires offer the same surface area as a larger, flat electrode, the proposed system can achieve excellent signal quality with smaller electrodes when tested on rats, said researchers in a study published in ACS Applied Materials and Interfaces.

Using zinc oxide nanowires “to increase the effective surface area drastically decreased the impedance value and enhanced the signal-to-noise ratio,” wrote scientists. “In vivo neural signal recordings showed that our neural probe can detect clearer signals.”

Related, Korean scientists from the Institute for Basic Science (IBS) combined gold and graphene into a wearable patch that is capable of monitoring glucose levels and delivering medication through an array of microneedles. The graphene-and-gold sensors can likewise monitor pH levels and temperature.