Liquid processing method can produce complete electronic devices

The team demonstrated the technique by producing a functional led array made of zinc oxide nanowires in a single beaker, instead of the several separate steps and devices required for conventional production. They say they were able to do so under relatively benign conditions, with moderate temperatures and without a vacuum. "People have done a good job of controlling the morphology of wires by other means - using high temperatures, high pressure, or subtractive processing. But to be able to do this under these benign conditions is attractive because it makes it possible to integrate such devices with relatively fragile materials such as polymers and plastics," said Brian Chow, a postdoc at MIT. According to Chow, control over the shapes of the wires had, until now, been a trial and error process. "We were trying to find out what the controlling factor was," he explained. "The key turned out to be the electrostatic properties of the zinc oxide material as it grew from a solution. Different compounds, when added to the solution, attached themselves electrostatically only to certain parts of the wire - inhibiting the wire's growth in those directions." While the work was carried out with zinc oxide nanowires, the MIT scientists believe the method could be expanded to different material systems. "Because the benign assembly conditions allow the material to be deposited on plastic surfaces, it might enable the development of flexible display panels, for example," he said. Other possible applications for the method include the production of batteries, sensors, and optical devices. Chow says the method has the potential for large scale manufacturing and could be used to make tiny implantable devices for the brain to provide both sensing and stimulation.