This is a frustrating limitation of 3D printing: the objects printed must be smaller than the machine that made them. Large machines are not suitable for printing large parts because they take up too much space and require a lot of time to print. Now, a new material reported in ACS Applied Materials & Interfaces can be used to 3D print small objects that expand when heated. The foam material can be used in construction, aerospace, and biomedical fields.
One type of 3D printing (stereolithography) creates objects by exposing a continuous layer of photosensitive resin to light patterns that cure the polymer into the desired shape. A dedicated stereolithography machine can be used to create large objects, but it is usually made by fixing smaller 3D printed components together. David Wirth, Jonathan Pokorski, and colleagues at the University of California, San Diego hope to develop an expandable resin that can be used to print large objects using inexpensive, commercially available 3D printers.
The researchers tested many different resin formulations to find a resin that allowed them to print out objects that expanded to a larger size when heated. They used the formula to 3D print hollow, spherical spheres. Heating the sphere in the oven will cause the volatile components of the resin to come out as a gas. This creates a porous, polystyrene foam-like material, which is 40 times larger than the original printed object. In this way, the team can also 3D print many other shapes, including boat charts, its expanded size can carry about 20 times the weight, and the wind turbine can generate a small amount of electricity in a larger size. Although this new material is not as strong as polystyrene foam, it can one day be used for cushioning, wings, buoyancy aids, and even an astronaut’s scalable habitat.