Nanowires could be the basis of tomorrow's advanced electronics, from cheap solar cells to high-resolution displays. But it's been difficult to arrange the tiny strands precisely. Ali Javey, an assistant professor of electrical engineering and computer science, has become a master at doing so. His latest tool for making high-quality circuits: a roller printer. He coats a glass cylinder with a catalyst and puts it in a chemical-vapor deposition chamber, where its surface sprouts nanowires. When the cylinder is pressed against a flexible piece of plastic or a silicon wafer, the tips of the nanowires cling to the flat surface; as the tube rolls, the wires are dragged and combed into straight rows before detaching from the roller. So far, Javey has used the technique to print transistors based on germanium, silicon, and indium arsenide nanowires. He has also printed arrays of light-sensing cadmium selenide nanowires, which can be used as photosensors for imaging applications. --Katherine Bourzac

Credit: Erik Pawassar