Programmable Magnets

Martin Hellman writes "A few weeks ago Popular Mechanics awarded one of its Breakthrough Awards for the invention of 'programmable magnets.' Instead of having a single North or South pole, these clever devices have an array of North and South poles. If a matching device with exactly the same array is aligned with the first one, they will experience strong repulsion, just like two single North poles do when brought near one another. If the matching device has the complementary array (North and South interchanged), with correct alignment the two devices will attract. But a slight misalignment will cancel most of the force. Other configurations are possible as well, allowing frictionless magnetic gears and exploding toys. The inventor, Larry Fullerton, used techniques similar to those from CDMA modulation. (Watch the intro video for a brief explanation. While I don't understand magnetism that well, I do understand CDMA and carrying over those ideas to magnetic arrays does make sense to me.)"

Re:Obligatory:

[Myopic]

Some people will need to be told about the joke [knowyourmeme.com].

How programmable though.

[Twinbee]

A decade or so back, I created something called "Super Magnet", and the whole idea was to create a system of atoms/magnets with completely customizable forces - a bit like an infinitely extendable version of what Nature does.

Yes, I know this is in software, but the results can be pretty cool:

http://www.youtube.com/watch?v=LTW09McfCjA [youtube.com]
http://www.youtube.com/watch?v=jdfSWsTBtyE [youtube.com]
http://www.skytopia.com/project/magnet/magnet.html [skytopia.com]

Bear in mind these animations are about 10 years old - modern hardware and algorithms would use many more magnets (though creativity counts for quite a bit too).

Re:Exploding toys?

[camperdave]

It's more of a spring loaded type of effect. The "correlated" magnetic field, instead of being completely attractive, or completely repulsive, is repulsive up to a certain distance, at which point it becomes attractive. So to arm the toy, you press the magnets together until they reach the attractive distance. This holds them together. To "explode" the toy, you separate the magnets (either by physical means, or by another magnet that cancels the attractive field), and the repulsive fields cause the parts to "explode".

Imagine a magnetic bowl with the rim being the north pole, and the bottom being the south. Now, imagine lowering the north end of a bar magnet down into the center of the bowl. At first, it will be repulsed by the north field along the rim of the bowl. However, once the end of the bar magnet is lower than the rim of the bowl, the field will force the bar magnet down, and it will be attracted to the bottom of the bowl. At this point, an upward blow large enough to knock the bar magnet loose, and past the lip of the bowl, will cause it to enter the repulsive area of the field, and it will "explode".

Magnetic gears?

[reg106]

The "frictionless" magnetic gear shown will still have friction in the bearing. The magnetic "teeth" will introduce a huge amount of backlash into the gear system. And you would run into problems if you tried to stack gears beside each other in a gearbox. The high pull-off force/low twist-and-pull force application is neat though. One limitation is that rare earth magnets tend to be brittle, and make a mess when they break.

To be clear though, magnets have been made with multiple poles for a long time, for example those flexible fridge magnets will often have alternating poles across their surface. Also, the pull off application is in many ways similar to the "switchable magnetic bases" [edmundoptics.com]. In these devices, the orientation of the magnetic is changed to force the field lines to go through the surface underneath, or to be contained within the base. The innovation in the present work is the use of coding theory to design the patterns.

Re:Hey kdawson...

[Dishevel]

Hey Tri ...
Please reply to posts you are actually talking about.

Re:Obligatory:

[tomkost]

They do deteriorate, but not generally due to interactions with other magnets. They deteriorate mostly due to molecular vibration (from heat or shock waves). This vibration can cause the domains to become unaligned.