A new 3D printer, developed by a team at the University of Wisconsin-Madison, is using different patterns of visible and UV light to provide it with the spatial control necessary to produce multimaterial parts successfully. To position various materials for the printing process, most multimaterial 3D-printing methods use separate reservoirs for the different materials. For this printer, the researchers chose to take a one-vat, multiple-component approach. They used digital light processing additive manufacturing (DLP-AM) to control chemical composition along all three axes of the printed object by simultaneously projecting more than one light source into a vat of photoresin. The top images show the digital design and its printed form. Purple corresponds to ultraviolet-cured stiff epoxide regions, whereas the gray regions are visible-light-cured acrylate regions that are soft and compliant. At the bottom, the logo for the 3D-printing group, MASC, is turned into a printed object composed of both stiff, opaque regions and soft, transparent regions. Courtesy of A.J. Boydston and Johanna Schwartz. Using different wavelengths of light, the researchers controlled which starting materials (monomers) were polymerized into different sections of the printed product. When they irradiated the monomers with visible wavelengths, they observed preferential curing of acrylate components. Under shortwave (UV) irradiation, a combination of acrylate and epoxide components were incorporated. This enabled production of multimaterial parts containing stiff epoxide networks contrasted against soft hydrogels and organogels. “At this stage, we’ve only accomplished putting hard materials next to soft materials in one step,” said professor A.J. Boydston. “There are many imperfections, but these are exciting new challenges.” Graduate student Johanna Schwartz next to the multimaterial printing setup that she built. Courtesy of A.J. Boydston and Johanna Schwartz. One of the hurdles the team faced was how to optimize the chemistry of the starting materials. Now, they plan to explore additional monomer combinations and whether different wavelengths can be used to cure the materials. Boydston also hopes to assemble an interdisciplinary team that can increase the impact of wavelength-controlled, multimaterial 3D printing. The researchers’ novel approach to multimaterial 3D printing could enable designers, artists, engineers, and scientists to create significantly more complex systems with 3D printing. Applications could include the creation of personalized medical devices, such as prostheses, or the development of simulated organs and tissues. Researcher Johanna Schwartz believes that using chemical methods to eliminate an engineering bottleneck is what the 3D-printing industry needs to move forward. “It is this interface of chemistry and engineering that will propel the field to new heights,” she said. “This is a shift in how we think about 3D printing with multiple types of materials in one object,” Boydston said. “This is more of a bottom-up chemist’s approach, from molecules to networks.” The research was published in Nature Communications (https://doi.org/10.1038/s41467-019-08639-7).