4-D printing remains in its early stages, It’s certainly too early to tell if it’s anything more than a buzzword, let alone if its promise will translate into practicality. But the sorts of people who bet on these kinds of things are betting on it.
And why not? Suppose a structure could unfold itself, like origami. Imagine if walls could flex or stiffen in response to shifting loads, or if a buried pipe could change shape to accommodate varying water flows — or to pump water via peristalsis, like your digestive system. Through 4-D printing, nothing is set in stone unless you want it to be.