By now, the technologies and applications of 3D printing have become well known. Not as widely understood is the latest development in additive manufacturing: using 3D printing to create objects that can “assemble” themselves in response to specific conditions or stimuli.
Evangelists call it “4D printing” because it adds the dimension of time to the process—time for the object to change shape in some predetermined manner after it has been given its initial shape by the 3D printing device. Think, for example, of a plumbing pipe that swells or contracts to accommodate the changing volumes of water running through it; or of an athletic shoe that changes its shape and “grows” features like cleats to suit the type of activity its wearer is performing.
To make 4D-printed objects perform in this way, the 3D printer must build them from responsive materials according to instructions that “tell” the material what to do when it encounters the triggering condition. This could be water, causing the object to unfold, coil, or otherwise reconfigure itself when it gets wet. Pressure, temperature, light, and UV radiation are other stimuli for 4D functionality.
The broad goal of 4D printing is to recast manufacturing as something that happens not when people and machines put things together, but when “programmable parts” assemble themselves into whatever the desired object happens to be. Self-assembly exists in the natural world in processes such as the replication of DNA. 4D printing is the analogous process for building things in the human-made world through the local interaction of their components.
Skylar Tibbits says that 4D printing promises breakthroughs in biology, material science, software, robotics, manufacturing, transportation, infrastructure, construction, the arts, and space exploration. He is the director of MIT’s Self-Assembly Lab and the most noted advocate of 4D printing and its uses. His TED talk is a good introduction to the principles and potential of the emerging technology.
“Emerging” means that there are no commercially available 4D-printed products—yet. Developmental projects for practical applications are under way. At the University of Wollongong in New South Wales, Australia, researchers have come up with a valve that closes itself when it detects hot water. The Somerville, MA, design studio Nervous System used a 4D design system it calls Kinematics to create a dress that conforms fluidly (and stylishly) to the movements of its wearer’s body.
Nervous System’s technology partner in the project was the 3D printing service Shapeways. Another significant collaboration for 4D printing is the one involving 3D printer manufacturer Stratasys and 3D software developer Autodesk in projects for Tibbits’s Self-Assembly Lab.
A good omen for any emerging technology, scientifically speaking, is the possibility that it may have military applications. In 2013, researchers from Harvard, the University of Illinois, and the University of Pittsburgh received an $855,000 grant from the U.S. Army Research Ofice to investigate how 4D printing might be used to make items capable of responding to battlefield conditions: for example, uniforms that can change camouflage patterns or resist hazards like shrapnel and poison gas.
The fact that uses for 4D printing remain almost purely speculative hasn’t stopped believers from positing a brisk commercial future for the technology. According to this report, for example, the industry said to be taking shape around manufacturing with programmable materials will have a compound annual growth rate of nearly 43% between 2019 and 2025.
How 4D printing will intersect with the two-dimensional kind is anyone’s guess. But, 4D printing proponents may want to recall that traditional printing has been making self-assembling products for years. These objects consist of interlinked parts that come together programmatically in new structures when a specific energizing force is applied: in this case, the opening of covers or the turning of a page.
They’re called pop-up books, and they’re still as intriguing as anything that ever came out of an additive manufacturing lab.