Just as 3D printers create objects that have three-dimensional characteristics, 4D printers create objects that have four dimensional characteristics, in that they include a dynamic component that causes their structure to change over time; relying on water, heat, or light to activate them. By using a multi-material printer, it’s possible to generate objects with the properties all in one go. Such “programmable materials” may one day mean that you can buy flat-pack furniture at IKEA, take it home, spray it with a garden hose and then watch it assemble itself! MIT is currently working on this exact thing!
Let’s think about what happens to a thin strip of wood if you get it wet: it warps, as different parts of the wood swell in slightly different ways. Typically, this is bad, because warping is unpredictable and related to the type of wood, the patterns in the grain of that wood, how and where it gets wet, etc. So if we could somehow predict the warping, we could find a piece of wood that we could deliberately warp into a shape that you want just by adding water. With 3D printing it’s possible to manufacture pieces of wood with whatever composition, thickness, and grain characteristics that you want. With a great understanding of how the material behaves, along with computer models, you can 3D print a piece of artificial wood that’s been “pre-programmed” using carefully constructed layers of various thicknesses and grain directions. It will warp itself from flat into exactly the shape you want, just add water! The MIT Self-Assembly Lab has been developing a variety of programmable materials, not just wood. So we could see pre-programmed materials such as carbon fiber in the future as well! Technology just makes our life easier doesn’t it?