Carnegie team harnesses warpage to 3D print self-folding plastics

Researchers at Carnegie Mellon University have developed a 3D printing process that creates flat plastic items that fold into predetermined shapes when heated.

Known as Thermorph, the method relies on a natural phenomenon called ‘warpage’ that sometimes occurs when printing thermoplastic. Generally a nuisance, the Carnegie team has adopted warpage to its advantage. It used software algorithms developed in-house to precisely control an off-the-shelf FDM (fused deposition modelling) printer, combining the plastic with rubber-like materials and depositing them in such a way as to encourage warpage.

The objects emerge from the 3D printer as flat, hard plastic. When the plastic is placed in water hot enough to turn it soft— but not hot enough to melt it — the folding process is triggered.

“The software is based on new curve-folding theory representing banding motions of curved area,” said Byoungkwon An, a research affiliate at Carnegie’s Human-Computer Interaction Institute (HCII). “The software based on this theory can compile any arbitrary 3D mesh shape to an associated thermoplastic sheet in a few seconds without human intervention.”

Using the new technique, the research group was able to create relatively complex self-folding shapes such as roses, boats, and rabbits. While these were all produced on a desktop scale, the fundamental science at play should also be applicable to larger objects, such as furniture that self-assembles using a heat gun, or flat pack emergency shelters that erect themselves under the heat of the sun. Self-folding materials also have the advantage of being quicker and cheaper to print than solid 3D objects.

“We believe the general algorithm and existing material systems should enable us to eventually make large, strong self-folding objects, such as chairs, boats or even satellites,” said HCII research intern Jianzhe Gu.

Group leader Lining Yao presented Thermorph and the team’s findings at a computing conference in Montreal, Canada this week.