Yes. It's true. After a little summer slow-down, it is time for the return of the Codex Futurius, this blog’s never-ending quest to explore the big science of science fiction. This question on futuristic materials was fielded by Sidney Perkowitz, a physicist at Emory University. Thanks much to Dr. Perkowitz for the solid (ha) info and to Jennifer Ouellette, the director the NAS’ Science and Entertainment Exchange (SEEx) program, for connecting us with him. Will we use metal in the future? What else would we build things out of? Might we use organic technology (machines and buildings made of or from biological organisms) instead?" In The Graduate, that iconic film from 1967, bewildered 20-something Benjamin Braddock (Dustin Hoffman) gets some career advice from a businessman who leans close and intones “I want to say one word to you. Just one word. Are you listening? Plastics.” Benjamin didn’t follow that advice, but the rest of the world did, and in spades. By 1979, global production of plastic had exceeded that of steel and is still growing, reaching over 200 million tons this year. There’s no doubt that plastic will continue to play a major role in how we make things, but it won’t replace everything. In some ways, plastic is the material of the future, the latest step in humanity’s long upward trek through the ages of stone, bronze, iron, and steel. The word "plastic" comes from Greek roots meaning “capable of being molded.” Compared to metals and other materials, plastic is infinitely versatile. With its ability to shape-shift and to take on different mechanical and optical properties, it shows up in a huge spectrum of applications from packaging and plumbing to toys, medical supplies, and computers. And unlike iron and steel, plastic doesn’t rust. But plastic also has problems that will prevent it from replacing metals any time soon. Its very durability can be an issue. Discarded plastic objects can survive for centuries in garbage landfills without degrading, and plastic artifacts have been found polluting the oceans far distant from any land. Also, what doesn’t seem to be widely appreciated, the raw material to make plastic comes from a resource we need to conserve, petroleum. On top of this, metals do some things better than plastic—just try cutting up an apple with a plastic knife. Copper and other metals are needed to conduct electricity through power grids; all plastic can do is insulate the current-carrying wires. However, plastic is making inroads relative to some materials such as wood, which is being replaced by plastic "lumber" in certain applications. Plastic also offers a possible way to actually construct things using biotechnology. Unlike metals, which are classified as inorganic, plastics are organic; they’re made of carbon, hydrogen, nitrogen, and oxygen, the same constituents as living things, which links plastic to biological products. For instance, under the right conditions, certain microorganisms can synthesize compounds called polyhydroxyalkanoates (PHAs). These display properties like those of artificial plastics, with the benefits that they’re not petroleum-based and are biodegradable. Researchers are investigating ways to mass-produce these bioplastics, for instance by bioengineering plants to create them. If you want to speculate even further, way past the idea of growing plastic rather than making it in factories, think about the science-fictionish possibility of bioengineering plants to produce plastic exactly in a desired shape from a drinking cup to a house. Current biotechnology is far short of this possibility, but science fiction has a way of pointing to the future. If bioplastics are the materials breakthrough of the 21st century, houses grown from seeds may be the breakthrough of the 22nd.