An Engineer in Wonderland – Nano-printing by explosive

02apr08explosives.jpg You can get a bit blasé about achievements at the various Fraunhofer Institutes in Germany. They are always doing clever things – take a look the ethylene sensor here: Infra-red sensor tunes fruit ripening But its Institute for Chemical Technology has excelled itself by proving that explosive blasting in miniature can be used to make tools for hologram production. I have seen explosive forming before – as a way of forcing aluminium sheet into moulds – but nothing with resolution “in the two-figure nanometre range” that Fraunhofer is claiming.

They are using a sheet of explosive behind a pattern to emboss that pattern into a steel sheet. “Nobody believed such a thing could be possible,” said project manager Gunter Helferich. With the right dosage, explosives enable a template to be copied with far greater accuracy than by conventional methods. Holograms are normally produced using an object, a laser, photo resist and etching to produce the master, which is electroplated with nickel. The peeled-off nickel becomes the production tool. It looks like, although I’m prepared to be corrected here, Fraunhofer is blasting the master straight into the steel to make a production tool that is harder than nickel – although I doubt the master is much good afterwards so there must be an intermediate step or two here. Apparently, “almost any structure, be it wood, leather, textiles or sand, can be rapidly and accurately impressed on metal in perfect detail with the aid of a sheet explosive”, said Fraunhofer, which is looking for industrial partners to develop the technique. ‘Alice’ By the way, the title An Engineer in Wonderland was inspired by the 1967 book ‘The Engineer in Wonderland’ by Professor Eric Laithwaite: champion of the linear induction motor.

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