Nanowire and nanotube production typically occurs in a furnace heated to between 600 and 1,000 degrees Celsius--temperatures that other electronic components cannot withstand. "One very big problem right now is figuring out how to assemble these nanowires or nanotubes onto a microchip in a way that is commercially feasible," notes Liwei Lin of the University of California at Berkeley. Lin and his colleagues developed a method that localizes the heating to the areas where they want the nanowires to grow by passing a current through specific sections of a microchip. They successfully manufactured silicon wires up to 10 microns long and between 30 and 80 nanometers in diameter. In addition, they produced carbon nanotubes five microns in length.
Although sections of the chip surface reached 700 degrees C, the surrounding areas remained cool and the entire process was carried out at room temperature. "This is a unique approach," Lin says. "This method allows the production of an entire nano-based sensor in a process similar to creating computer chips. There would be no post-assembly required."