Graphene is an unusual substance that the research team says makes an excellent choice of material for its minute sensors intended for measuring the electrical impulses constantly coursing throughout the human nervous system. The reason for this is that graphene consists of a single layer of carbon atoms just one atom in width. The graphene atoms, which form a hexagonal lattice, make up an active layer in the sensors with three very useful characteristics. They react extremely sensitively to the weak cell impulses, are well-tolerated biologically and can be mounted onto a pliable substrate.
"This is ideal for the applications that we have in mind for these components," explains Dmitry Kireev, an expert in microtechnology at the Institute of Complex Systems (ICS-8) in Jülich. "The long-term goal is to develop a brain-computer interface." The idea is for the implants to detect signals in the heart of the central nervous system and relay them externally, for example to give amputees direct control over a prosthesis. Although the researchers point out that there is a long way to go yet, they say that the sensors can already help them understand a great deal about how nerve cells function.
So far, Kireev has managed to create two different architectures for the microsensors. He explains that in the more basic scenario, the thin layer of graphene simply forms a microelectrode that can record the impulses from the nerve cells and pass these on. "Thanks to the low background noise presented by this constellation, it delivers very clear signals." The second architecture is rather more complex. In this case, the graphene layer forms part of a field-effect transistor (FET) on a component, which functions as a tiny valve for electric current. Ultimately, the aim is to not only read nerve impulses but also stimulate cells precisely. "It's not only individual neurons that process bioelectric signals but also heart cells. So it's perfectly conceivable that we could use this technology to manufacture a smart pacemaker," Kireev reveals.