Inside each M-Block is a flywheel that can reach speeds of 20,000 revolutions per minute; when the flywheel is braked, it imparts its angular momentum to the cube. On each edge of an M-Block, and on every face, are cleverly arranged permanent magnets that allow any two cubes to attach to each other...

To compensate for its static instability, the researchers’ robot relies on some ingenious engineering. On each edge of a cube are two cylindrical magnets, mounted like rolling pins. When two cubes approach each other, the magnets naturally rotate, so that north poles align with south, and vice versa. Any face of any cube can thus attach to any face of any other.

The cubes’ edges are also beveled, so when two cubes are face to face, there’s a slight gap between their magnets. When one cube begins to flip on top of another, the bevels, and thus the magnets, touch. The connection between the cubes becomes much stronger, anchoring the pivot. On each face of a cube are four more pairs of smaller magnets, arranged symmetrically, which help snap a moving cube into place when it lands on top of another.

As with any modular-robot system, the hope is that the modules can be miniaturized: the ultimate aim of most such research is hordes of swarming microbots that can self-assemble, like the “liquid steel” androids in the movie “Terminator II.” And the simplicity of the cubes’ design makes miniaturization promising.

Although Philip K. Dick fans are rightly thinking about the autofac from his 1955 short story of the same name, or even the nanomachine swarm from Stanislaw Lem's excellent 1954 novel The Invincible, I have an older and perhaps more exact science fictional prediction of this idea.

In his amazing 1920 short story The Metal Monster, Abraham Merritt imagines a robot that is constructed of smaller metal pieces able to move on their own.

Faster the cubes moved; faster the circle revolved; the pyramids raised themselves, stood bolt upright on their square bases; the six rolling spheres touched them, joined the spinning, and with sleight-of-hand suddenness the ring drew together; its units coalesced, cubes and pyramids and globes threading with a curious suggestion of ferment.

With the same startling abruptness there stood erect, where but a moment before they had seethed, a little figure, grotesque; a weirdly humorous, a vaguely terrifying foot-high shape, squared and angled and pointed and ANIMATE—as though a child should build from nursery blocks a fantastic shape which abruptly is filled with throbbing life.

Again the sibilant rustling—and cubes and pyramids and spheres were gone.

"Goodwin!" he whispered. "What—what were they?"

"Metal," I said—it was the only word to which my whirling mind could cling—"metal—"

"Metal!" he echoed. "These things metal? Metal—ALIVE AND THINKING!"
(Read more about Abraham Merritt's living metal cubes)