Nanotube Electrodes Spear Nerve Cells

To better understand how the brain works, neuroscientists plunge fine-tipped electrodes inside nerve cells to measure the electrical signals they transmit. Oftentimes, researchers use glass-encased electrodes called micropipettes, but the probes can be brittle, making them difficult to work with. Metal electrodes have been tried, too, but it’s difficult to sharpen their tips sufficiently to poke them into cells. For a more robust alternative, researchers at Duke University, led by Bruce R. Donald and Richard Mooney, have developed ultrafine electrodes made of carbon nanotubes for nerve cell recording (PLoS One 2013, DOI: 10.1371/journal.pone.0065715). “With carbon nanotubes, we can make something very strong and conductive that is pointy like a harpoon,” Donald says. To make the 1- to 2-mm-long spears, the Duke researchers used dielectrophoresis to draw nanotubes out from the end of a tungsten wire, and they stiffened the whole assembly by running current through it. Then they coated the electrode with an insulating compound and etched its tip with a focused ion beam. Using the new electrodes, the team successfully recorded signals from inside single nerve cells in slices of mouse brain and from outside nerve cells in the brains of live mice.