Zinc oxide nanostructures are directly synthesized in parallel microfluidic channels (held by the metal frame) by flowing reactants through the tubing. The microfluidic structure not only creates the device, but also becomes the final packaged functional LED device itself.
CAMBRIDGE, US: Researchers at MIT have found a way to grow submicroscopic wires in water with great precision, using a method that makes it possible to produce entire electronic devices through a liquid-based process.
The team demonstrated the technique, called hydrothermal synthesis, by producing a functional light-emitting diode (LED) array made of zinc oxide nanowires in a microfluidic channel. They were able to do so on a lab bench, essentially using a syringe to push solution through a capillary tube one-tenth of a millimetre wide, without expensive semiconductor manufacturing processes and facilities.
Unlike larger structures, with nanomaterials, differences in shape can lead to dramatic differences in behaviour. “For nanostructures, there’s a coupling between the geometry and the electrical and optical properties,” explained Brian Chow PhD ’08, co-author of a paper describing the results that was published July 10 in the journal Nature Materials. The system Chow and his colleagues developed can precisely control the aspect ratio of nanowires to produce anything from flat plates to long, thin wires.
Control over the shapes of the wires has until now been largely a trial-and-error process. “We were trying to find out what is the controlling factor,” explained Jaebum Joo PhD ’10, now a senior research scientist at Dow Chemical Co, who was the lead author of the paper.
While this work was done with zinc oxide nanowires, MIT scientists believe the method, “Can be expanded to different material systems,” Joo said, adding that, “Zinc oxide has potential for large-scale manufacturing.”
Manu Prakash PhD ’08, now an assistant professor of bioengineering at Stanford University, said this was a very interdisciplinary project that emerged when he (studying applied physics), Joo (studying nanomaterials) and Chow (in applied chemistry) were close friends in graduate school. They talked about the inefficiency of present methods, where electronic circuits are first built, then packaged and finally tested. “All these things could be done in one shot,” Prakash said, and that’s what they were able to demonstrate in the work.
Christopher Murray, University Professor of Chemistry and Materials Science and Engineering at the University of Pennsylvania, called this paper a “Valuable contribution.” Murray was not involved in this research.
The research was carried out with Media Lab associate professors Edward Boyden and Joseph Jacobson and was funded by the MIT Centre for Bits and Atoms, the MIT Media Lab, the Korea Foundation for Advanced Studies, Samsung Electronics, the Harvard Society of Fellows, the Wallace H Coulter Early Career Award, the NARSAD Young Investigator Award, the National Science Foundation and the NIH Director’s New Innovator Award.
(C) MIT News