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Creating Connections.
Yim’s first-generation or “G1” PolyBots are “a test bed for doing experiments with different gaits,” he says. Yim connects several G1 modules by hand to produce different robot body shapes, beginning with a snake’s. He pauses before attaching the next module, which is essentially a squat box-shaped hinge. “These guys have basically two parts: the modules and the wires that connect them. Each module has a computer and four identical connectors” on its top, to which green and white wires are attached. “The wires pass power and communications from module to module.”

A motor in the module, driven by the onboard computer, can swivel each of the hinge’s two halves in either direction, Yim says, flexing the device’s joint with his hands. As the snake grows before him, Yim explains that the modules are actually capable of snapping together on four sides, “so they can form a cross as well as a chain.” Small wires touch when two modules are joined-“That’s how a module sees who its neighbors are.”


From Many, One.
Though each module stores its own basic software for detecting neighboring modules and actuating its motor, Yim says, the newly formed snake needs a central “brain” to organize the modules’ movement. Once Yim finishes assembling the chain, he attaches the brain-a small blue circuit board dangling from a couple of wires (not visible in this image)-to an open connector on one of the modules.

The snake sits silently for a few seconds, its green light-emitting diodes blinking. “What’s happening,” says Yim, “is that each module is talking to the others and to the brain. They’re figuring out that All of us modules are in a line, so this means we’re in the shape of a snake,’ and the brain is about to say, Okay, I recognize the snake shape, now let’s move like a snake.’” At that moment, the chain springs into life; its modules bend upward and downward in waves, driving the assembly forward with each undulation. “Kids actually love it,” says Yim. “It looks very biological. It crawls over their hands, and they touch it and go, Eeww.’”

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