Growing nanowires vertically has been within our power for some time now, but growing them horizontally, and directly on a surface you might actually want? That's harder. Researchers at the Weizmann Institute of Science think they've figured out the trick, and have coaxed nanowires to grow in nice straight lines on sapphire crystals. This makes the nanowires more directly useful for electronics.
They use miscut C-plane sapphire, which produces a series of parallel nanoscale grooves in the surface of the crystal. Then, using the well established vapor-liquid-solid growth method, the nanowires are teased out along the furrows, resulting in long, horizontal, perfectly aligned wires. In this case the researchers used nickel catalyst nanoparticles to produce galium nitride nanoparticles, which are commonly used in electronics.
This method has produced nanowires far longer than other horizontal types, and the researchers have already used it to craft nanowires up to one millimeter in length, which is comparable to vertically grown nanowires. The horizontal nanowires had optical and electronic properties on the same level as their vertical counterparts, too. Get ready for crystal radios to come back into style, on the nano scale.