The researchers built up layers of their SWNTs to produce a film that is electrically conducting even at a thickness of just a few nanometers. They next grew neuron precursor cells on this film. These precursor cells successfully differentiated into highly branched neurons. A voltage could then be applied, lateral to the SWNT film layer, and a so-called whole cell patch clamp used to measure any electrical effect on the nerve cells. When a lateral voltage is applied, a relatively large current is carried along the surface but only a very small current, in the region of billionths of an amp, is passed across the film to the nerve cells. The net effect is a kind of reverse amplification of the applied voltage that stimulates the nerve cells without damaging them.
Kotov and his colleagues report that such devices might find use in pain management, for instance, where nerve cells involved in the pain response might be controlled by reducing the activity of those cells. An analogous device might be used conversely to stimulate failed motor neurons, nerve cells that control muscle contraction. The researchers also suggest that stimulation could be applied to heart muscle cells to stimulate the heart.