Although a great many people like the “prestige” that comes with the natural color of their gold jewelry, teeth or vacuum cleaners, things are about to get a little more complicated – scientists from the University of Southampton have now devised a technique that causes gold (or other metals) to be seen in a variety of other colors ... green gold, anyone?
Unlike processes such as anodizing, in which colored films are added to metal surfaces, the Southampton technology works by actually altering the gold itself. Tiny raised or indented patterns are embossed onto its surface, changing the way that it absorbs and reflects light. Depending on the shape, height and/or depth of the pattern, that reflected light can be seen as any one of a number of colors. Different patterns could even be applied to the same object, causing different parts of it to take on different colors.
“This is the first time the visible color of metal has been changed in this way,” said project leader Prof. Nikolay Zheludev. “The colors of the objects we see all around us are determined by the way light interacts with those objects. For instance, an object that reflects red light but absorbs other wavelengths will appear red to the human eye.”
Other metals, such as silver and aluminum, can also be “colorized” using the technique. Along with its obvious applications in fields like jewelry-making, it has been suggested that the technology could additionally find use in making items such as banknotes harder to forge.
The patterns are presently being applied using an existing technique known as ion beam milling, which is described as being similar to sand-blasting on the atomic scale. However, the scientists believe that industrial-scale processing would be possible via methods such as nano-imprint, in which a master template is used to stamp out patterns on surfaces.
The university has filed for a patent on the technology, and is looking into its commercialization.
Source: University of Southampton