Credit: © 2007 ACS

Whereas many nanoscientists look to nature for inspiration, other researchers rely on nanotechnology to tell them more about natural systems. An example of this is the use of arrays of ultrafine electrodes to explore how electrical signals move along neurons, as demonstrated in this image of the electrical activity in a slice of rat brain recorded by Barclay Morrison III and colleagues at Columbia University and the Oak Ridge National Laboratory (Yu, Z. et al. Nano Lett. doi:10.1021/nl070291a; 2007).

Morrison and co-workers started by preparing an array of 40 electrodes — each made of vertically aligned carbon nanofibres — on a silicon wafer using standard fabrication techniques. The array was then cleaned and coated with proteins to make the surface compatible with neural cells. The brain slice, bathed in artificial cerebrospinal fluid, was placed on the array and the spontaneous electrical activity was recorded. The array was also able to detect responses when a constant current was applied to evoke a response, or when chemicals were added to induce epileptic activity.

The image above shows the electrical activity measured at different positions along the array (vertical axis) as a function of time (horizontal axis) in response to electrical stimuli being applied to two of the electrodes. Electrical activity is shown in units of mV mm−2 (red for positive values, blue for negative).

This new tool might allow researchers to record multiple electrical signals simultaneously with high spatial resolution, and improve our understanding of the complex neuronal circuitry in the nervous system.