A line is the shortest distance between two points, but “A-line,” a 4D printing system developed at Carnegie Mellon University, takes a more circuitous route.

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One-dimensional, “line”-shaped plastic structures produced with the A-line system can bend, fold and twist themselves into predetermined shapes when triggered by heat.

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3D-printed objects that later change shape are the very definition of 4D printing. But the process takes on special qualities when the objects can fit through narrow openings.

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A rod inserted through a narrow bottleneck, for instance, might transform into a hook to fish an object out of the bottle. Or a long, thin fastener inserted through holes in the seat of a chair might lock a chair leg into place. The A-line method also can be useful in making compliant devices, such as coil springs and tweezers. These are difficult to produce in […]

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