When these spaghetti-like materials were embedded into the alginate hydrogels, they crisscrossed their way through the gel to create porous, conductive pathways through which electricity could travel. If you throw something shorter and rounder on the floor, like rice, many of the grains won't touch at all,' said Tringides. It's a bit like throwing a box of uncooked spaghetti on the floor-because the noodles are all long and thin, they're likely to cross each other at multiple points.

'Part of the advantage of these materials is their long and narrow shape. The vast majority of electrodes are made of metal because metals are highly electrically conductive-but also very stiff and inflexible.Īfter many experiments and late nights in the lab, the team identified a combination of graphene flakes and carbon nanotubes as their top candidate. Now that the team had a material that could flex and flow around tissues, they had to invent an electrode that could do the same thing. In contrast, the alginate hydrogel stayed in position the whole time and retained its brain-like shape after removal. When they left the materials on the mock brains for two weeks, the elastic material had substantially moved from its original location and immediately sprang back into its original shape when removed from the underlying mock tissue. The alginate hydrogel had double the amount of contact with the underlying mock brain compared to the other materials, and was even able to get down into some of the brain's many deep grooves. They then placed their hydrogel onto a fake 'brain' made from gelatin-like agarose, and compared its performance to that of a plastic material and an elastic material.

After experimenting with different types of hydrogels, they settled on a version that most closely matched the mechanical properties of brain and heart tissue. The team's first task was to test whether their alginate hydrogels could successfully conform to living tissues. Credit: Wyss Institute at Harvard University These materials criss-cross each other at many points, creating a continuous path for electric current flow. A scanning electron microscope (SEM) image shows a close-up of the electrode’s graphene flakes and carbon nanotube components.

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