Many beasts, buildings, and beauties greet children who open pop-up books: a Tyrannosaurus rex with jaws agape, elaborate medieval castles with soaring towers, the Statue of Liberty with her torch held high. These detailed objects take their three-dimensional shape with the turn of a page, arising from intricately folded paper. Today, chemists and engineers are making their own sophisticated versions of pop-up structures. What they lack in whimsy, they may someday gain in practical function.
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These objects, which begin as two-dimensional structures, fold themselves into final, functional three-dimensional shapes. Self-folding is one of the methods in a broader category called self-assembly. In that strategy, scientists design structures that build themselves out of specific components, says George M. Whitesides, a chemist and materials scientist at Harvard University. Self-assembly “is a strategy for making complex, multicomponent, three-dimensional things,” he says.