Scientists were able to perform these measurements by an arrangement of microelectrodes – a network of small tubes – inserted into the cell membrane. But this approach is limited. Researchers were only able to determine the voltage in certain cells that had electrodes plugged into them.
“Recording a single point voltage – say, in the brain – is like wanting to watch a movie by looking at a single pixel on your computer screen. You can know how things are going, but you can’t see the plot, you can’t see the correlation of information at different points in space. space, ”Cohen said. The new graphene device produces a more complete picture because it records the voltage at each point where tissue and carbon atoms touch.
“What we were able to do using our graphene tool was photograph the entire surface simultaneously,” said Halleh Balch, lead author of the study, who was a PhD student at Berkeley during the experiment. (He is now a postdoctoral researcher at Stanford.) This is partly due to the unique properties of graphene. “Graphene is atomically thin, which makes it very sensitive to the local environment, because basically every part of its surface is an interface,” he said. Graphene also conducts electricity well and is relatively difficult, which makes it a long -standing experiment among quantum physicists and materials scientists.
But in the field of biological sensing, it’s more to newcomers. “The method itself is quite interesting. It’s novel, in the sense that graphene is used,” said Gunther Zeck, a physicist at Vienna Technical University who was not involved in the study.He has worked with microelectrodes in the past, and he suspects that graphene -based devices may be be real competition for them in the future.Making large microelectrode stacks can be very complex and expensive, Zeck said, but making large graphene sheets may be more practical.The new device is about 1 square centimeter, but graphene sheets are thousands of times more large are already commercially available.By using them to make “cameras”, scientists can detect electrical impulses to larger organs.
For more than a decade, physicists have known that graphene is sensitive to voltages and electric fields. But combining that view with the reality of untidy biological systems poses design challenges. For example, because the team did not insert graphene into the cell, they had to increase the influence of the cell’s electric field on the graphene before recording it.
The team used their knowledge of nanophotonics – a technology that uses light at the nano scale – to translate vague changes in graphene reflectivity into detailed descriptions of the electrical activity of the heart. They are coated with graphene on a waveguide, a glass prism coated with silicon and tantalum oxide, which creates a zigzag path for light. Once light hits the graphene, it enters the waveguide, which bounces it back onto the graphene, and so on. “This has increased the sensitivity we have, because you go through the surface of graphene many times,” said Jason Horng, a study author and Balch lab partner during his PhD. “If graphene has some change in reflectivity, then that change will be amplified.” This magnification means that small changes in the reflectivity of graphene can be detected.
The team also managed to capture the mechanical motion of the entire heart – the reduction of all cells at the beginning of the heartbeat and their relaxation later. As the heart cells pulsate, they drag onto the graphene sheet. That causes the light that leaves the graphene surface to be slightly refracted, in addition to changes in the electric field of the cell that is already present in its reflection. This led to an interesting observation: When the researchers used a muscle relaxant drug called blebbistatin to prevent the cells from moving, light -based recordings showed that the heart had stopped, but voltage was still spreading through the cells.