To hell with plain old 3-D printing. With “metamaterials,” you can not only 3-D print the shape of an object, but also the internal microstructure. What that means, given where the technology is now, is a handful of relatively useless household tools. But in terms of long-term application, the creators of the technology, a group of researchers at the Hasso-Plattner Institut in Germany, say their goal is to eliminate the need for assembly. A noble goal indeed in the age of Ikea tools and furniture.