There are many different types of 3D printing technologies. The most familiar — inkjet — has been around for some 20 years. But until now, it has been difficult to create 3D-printed structures with the intricate hollow features associated with complex origami because removing the supporting materials necessary to print these structures is challenging. Further, unlike paper, the 3D-printed materials could not be folded numerous times without breaking. Making such structures has involved multiple steps, more than one material, and assembly from smaller parts.
Researchers developed an integrated system for manufacturing complex origami using a relatively new kind of 3D printing called Digital Light Processing (DLP) to create groundbreaking origami structures that are not only capable of holding significant weight but can also be folded and refolded repeatedly in an action similar to the slow push and pull of an accordion. When first reported, these structures, or “zippered tubes,” were made of paper and required gluing. In the current work, the zippered tubes — and complex structures made out of them — are composed of one plastic (a polymer) and do not require assembly.
DLP has been in the lab for a while, but commercialization only began about five years ago. Unlike other 3D printing techniques, it creates structures by printing successive layers of a liquid resin that is then cured, or hardened, by ultraviolet light. For the current work, the researchers first developed a new resin that, when cured, is very strong — it can be folded hundreds of times without breaking. The resin, in turn, is key to an equally important element of the work: tiny hinges. These hinges, which occur along the creases where the origami structure folds, allow folding because they are made of a thinner layer of resin than the larger panels of which they are part. (The panels make up the bulk of the structure.)
Together, the new resin and hinges worked. The team used DLP to create several origami structures ranging from the individual origami cells that the zippered tubes are composed of to a complex bridge composed of many zippered tubes. All were subjected to tests that showed they were not only capable of carrying about 100 times the weight of the origami structure, but also could be repeatedly folded and unfolded without breaking.