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.)"