Hiding Messages In Magnets

Magnets have always been fun, particularly since the super-powerful neodymium type became readily available. You can stack them up, pull them apart, or, if you really want, use them for something practical. Now [Adric] has shown us a new use for them entirely – by writing hidden messages on them.

It’s a remarkably simple hack, but ingenious all the same. [Adric] was pretty sure that the Quelab hackerspace laser wasn’t powerful enough to cut or etch a nickel-plated neodymium magnet. However, they suspected it would have just enough power to heat localised parts of the magnet above the Curie temperature, where the magnetic properties of the material break down.

Thus, the laser cutter was set up to run a few passes over some neodymium magnets. By placing a magnetic viewing film over the magnet, it’s possible to make the etched pattern visible. There was also some incidental visible marking of the magnet surface, which [Adric] thinks is due to the tape applied to the magnet before the laser processing.

For those of you operating spy rings in deep cover, you’ve now got a new way to send them secret messages. Just be sure to check in with the local postal service as to their policies regarding giant magnets in the post. Then you can contemplate whether you have the ability to sense magnetic fields.

12 thoughts on “Hiding Messages In Magnets

    1. Nice video find, congrats.
      There are many applications for magnets with immense permutations for even simple array type devices, I’d expect more commercial products find their way to doing more useful things. It’s a pity that getting to the rare earth elements is do far costly and fraught with pollution issues…

    1. How about gutting a DVD Writer for it’s LASER diode? You could disguise it in almost any package. If your target is a blackbody you might be able to reach Curie within a few seconds. You could pop black baloons with it from across the room. You could light matches too.

  1. Couldn’t you just print some iron filament in the middle of a 3D print, and encapsulate it with regular thermoplastics? Then magnetize the ferromagnetic material?

    1. Probably sure though wouldn’t be that strong a magnet, I’d grab some old rare earth magnets heat past Curie point (only just) strip the plating, chill them & crush into powder then mix appropriate ratios or fill voids in the 3D print, seal with resin then do the pulse thing with appropriate device, all good fun :-)

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