07/17/2012
Growing LED lights on paper
The same chemical used as a pigment in breakfast cereals could lead to the creation of LEDs that are grown or printed on the surface of paper.
To create the printable diodes, it is necessary to first grew nanometer-sized zinc oxide crystals by coating paper in a polymer, seeding it with a solution containing zinc, and then coating it again with another polymer. The paper is then dipped in a mixture that encourages the zinc to grow into upright hollow rods, with yet another polymer added to keep the rods isolated from each other. Scraping away portions of the top polymer layer exposes the nanorods, which, when connected by silver electrical contacts, light up when expose to an electrical charge.
To create printable ZnO nanorods, one can use ultrasound to remove the rods and then mix them with an ink-containing solution. Using a conventional silk-screening machine, it is possible to print the ZnO on a piece of paper treated similarly to the one used to grow the crystal. The printed zinc also light up when a charge is applied to the paper.
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