Imagine a pair of running shoes that grow spikes on their soles to gain traction when it starts to rain in the middle of a run, or camouflage material that changes color as the light changes. Those are just some of the applications that might become possible with a new technique known as 4D printing, developed by Stratasys Ltd., Autodesk, Inc., and Self-Assembly Lab at MIT.
The concept starts with additive manufacturing (3D printing), in which a machine builds a three-dimensional object by depositing successive layers of a material—polymers, resins, metals, ceramics—in almost any shape a designer can imagine. 3D printing has been garnering headlines and gaining a foothold in the world of manufacturing in recent years. The industry analysis firm Wohlers Associates says the worldwide market for 3D printing products and services reached $2.2 billion in 2012. Now some researchers are taking the next step by adding a fourth dimension—time.