Nano Lett. 12, 3391–3398 (2012)

Making the electrodes in neural prosthetic devices small and flexible reduces the inflammation and scarring they cause. However, most materials are unable to deliver a sufficiently high charge per area, and have too high an interfacial impedance when they are fashioned into sufficiently small electrodes. The high electron mobility and surface area of carbon nanotubes recommend them as electrodes, but their performance at small dimensions and their long-term biocompatibility remain an issue. Nicholas Kotov and colleagues at the University of Michigan have now demonstrated that gold nanoparticle electrodes may be a better choice for neural prosthetics.

The researchers constructed two small electrodes, one from carbon nanotubes and one from gold nanoparticles. Layer-by-layer assembly was used to ensure that each electrode had the same thickness (around 100 nm). The impedance of the gold nanoparticle electrode was measured to be three times lower, and the charge storage capacity (a measure of available charge per area) ten times higher, than the carbon nanotube electrode. Moreover, a large body of clinical data supports the long-term biocompatibility of gold. The gold electrode performance benefited from a high surface area, and from good connectivity among nanoparticles.