When the Pieces Put Themselves Together Instead of assembly lines, what if manufacturing moved to self-assembly lines? There is something counterintuitive about seeing toys and furniture that spring together simply when their pieces are shaken around and around. Doesn't this go against the principles of entropy we learned in high school science, where order is supposed to dissolve into disorder? Actually, no. Self-assembly is a well-studied phenomenon on the molecular level - snowflakes, proteins, viruses - and one of the driving forces in nanotechnology. But researchers are taking principles from microbiology and applying them on the macro level - furniture, infrastructure and even buildings for space. Skylar Tibbits, a researcher at the Massachusetts Institute of Technology's architecture school, has already built a stool, a robot and toys this way. Arthur Olson, a molecular biologist at the Scripps Research Institute, started collaborating with Mr. Tibbits after they discovered that they had both been designing self-assembling toys inspired by microbiology. "We have the same principles, but different applications and very different scales," Dr. Olson said. Certain principles govern self-assembly. First, there needs to be a blueprint of the ultimate form. Second, the system needs to have forces of attraction that bring together the parts. These can either be magnets or electrostatic forces. Third, error correction has to allow the pieces to "fix" themselves when they assemble in the wrong way. Fourth, an external energy source is needed to activate the assembly. On the molecular level, this is often heat, but on the human scale it can be simple shaking. It is actually this external energy source that allows self-assembly to seemingly violate the principle of entropy, since entropy is a law that applies only to isolated systems. Inspired by these principles, Dr. Olson has been creating self-assembling toys on his 3-D printer and selling them at Science Within Reach for several years. A set of similar toys was manufactured by Mr. Tibbit and Dr. Olson and made available at the TEDGlobal conference in Edinburgh last month. Those toys are based on biological forms - an enzyme, a protein, a virus - and are made up of four, eight, or 12 plastic parts with tiny magnets inside. When the glass flasks are shaken, the plastic parts jumble together, link with the magnets and then grow into spherical structures. The more parts in the flask, the easier it is for the pieces to come together, Mr. Tibbits explained. Specifically, the toys mimicked satellite tobacco necrosis virus, which infects plants; ferritin, a protein that stores iron inside bodies; and catechol dioxygenase, a crucial enzyme in the metabolism of soil bacteria. In the case of the toys, the geometry is set by the shapes chosen by the researchers; the attraction is provided by the small magnets, which are aligned to create spheres; and the energy is provided by the shaking of the flask. As for error correction, small partially assembled pieces that don't fit together well will fall apart under continued shaking. But the larger structures become more stable as more magnetic bonds hold them together, making them harder to break apart. Mr. Tibbits's work focuses on taking such self-assembly principles to a larger level, with furniture, buildings and machines. "Construction at human scale is brute force," he said. "In extreme environments, we don't know how to build things." Self-assembly is most useful where human hands have difficulty bolting things together - outer space, extreme cold, free fall and deep oceans, he says. In those conditions, the surrounding environment could provide the energy source that sparks the components to interact and join. Underwater, it would be wave energy. And in extreme cold, it could be wind. Mr. Tibbits has already created a spherical and geometric stool that self-assembles as the pieces tumble together in a giant spinner, a larger version of the toys. Next up, Mr. Tibbits says, he is talking with a company that works in space for a structure that it can potentially use.