On the subject of the printing of things equivalent to financial institution notes or passports, you need to use a way that is not straightforward to copy. Swiss scientists have developed simply such a know-how, which prints by taking materials away as a substitute of depositing it.
Led by PhD pupil Sebastian Mader and Prof. Olivier Martin, a crew on the EPFL analysis institute initially got down to develop a cloth that fully absorbs gentle.
What they got here up with was a clear Plexiglass substrate lined with a layer of aluminum on the underside, magnesium fluoride within the center, and chrome on high (on the floor). Every layer is only a few nanometers thick, and the mixture does certainly take up all wavelengths of sunshine, leading to what's perceived as a "excellent" shade of black.
Martin, nevertheless, questioned what would occur if he used a laser to take away the layer of chrome. Upon doing so, he found that the remaining layers of magnesium fluoride and aluminum fashioned a extremely reflective mirror. Eradicating these layers in flip revealed the clear Plexiglass. Due to this fact, when a sheet of coloured paper was positioned on the again of the Plexiglass, that background shade confirmed by way of.
The scientists moreover discovered that by exactly controlling the length of laser gentle publicity, it was attainable not solely to get stable black, mirrored and background colours, but in addition to get delicate gradations between them (equivalent to half black, half mirrored).
Down the street, through the use of a skinny, versatile, clear substrate instead of the Plexiglass, it's hoped that the know-how might be utilized in purposes the place safety and fraud prevention are of the utmost significance.
The analysis is described in a paper that was not too long ago printed within the journal Gentle: Superior Manufacturing.
Supply: EPFL
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