ADVANCED MATERIALS & PROCESSES | OCTOBER 2024 60 3D PRINTSHOP ECOFRIENDLY 3D-PRINTED LIGNIN COATING Researchers at the German Institutes of Textile and Fiber Research Denkendorf (DITF) are using a 3D-printing process to make a coating for gloves that is an alternative to oil-based polymers. The biopolymer lignin is a natural component of plant cells that is produced in large quantities as a by-product of paper manufacturing. The scientists developed biopolymer compounds containing lignin, which were used to produce thermoplastic materials that can be processed using 3D printing. Lignin has few polar groups, which makes them hydrophobic and therefore insoluble in water. For this reason, they biodegrade slowly. This makes them particularly suitable for durable coating materials. The research project shows that the use of lignin not only offers ecological benefits, but that protective gloves coated with it are also particularly durable, resistant, and meet safety standards. ditf.de/en/. MICROWAVE TECHNIQUE CURES MATERIALS A new process developed at Lawrence Livermore National Laboratory (LLNL) called microwave volumetric additive manufacturing (MVAM) allows designers to cure a wider range of 3D-printed materials. Microwaves reach deeper into materials, making them an ideal candidate for curing a variety of resins, including resins that are opaque or loaded with additives, researchers say. In a recent paper published in Additive Manufacturing Letters, LLNL researchers describe the potential of microwave energy to penetrate a wider range of materials compared to light-based volumetric additive manufacturing (VAM). While VAM techniques like computed axial lithography allow for rapid printing of complex 3D shapes in a single operation and eliminate the need for support structures, VAM relies on specific materials, primarily transparent and low-absorbing resins, which restricts the use of opaque or composite materials. “One major impact [of MVAM] is if we can maintain a feedstock of materials surrounded with a microwave antenna array, we can now think about creating simple large geometries, as well as complicated large geometries, at scale using microwaves,” says LLNL research scientist Saptarshi Mukherjee. Co-author Maxim Shusteff adds, “Microwave volumetric AM opens up a new frontier in 3D printing by enabling the use of opaque and filled materials, which were previously challenging to work with,” Shusteff says. “This can be a path toward large-format parts with enhanced material properties.” llnl.gov. APPLYING AI TO 3D PRINTING Researchers at Washington State University developed an algorithm to train and optimize 3D-printing settings on intricate designs. The algorithm learned to identify, and then print, the best versions of kidney and prostate organ models, printing out 60 continually improving versions. Professor Kaiyan Qiu has done research for several years in developing complex, lifelike 3D-printed models of human organs. They can be used, for instance, in training surgeons or evaluating implant devices, but the models must include the mechanical and physical properties of the real- life organ, including veins, arteries, channels, and other detailed structures. The team used an AI technique called Bayesian Optimization to train and find the optimized 3D-printing settings. Once it was trained, the researchers were able to optimize three different objectives for their organ models—the geometry precision of the model, its weight or how porous it is, and the printing time. The researchers first trained the computer program to print out a surgical rehearsal model of a prostate. Because the algorithm is broadly generalizable, they could easily change it with small tunings to print out a kidney model. “That means that this method can be used to manufacture other more complicated biomedical devices, and even in other fields,” says Qiu. wsu.edu. Printed textile with a lignin coating for use in gloves. Courtesy of DITF. Proposed MVAM system. Superposition of beams from antenna array focus energy to arbitrary locations, enabling complex patterning. Courtesy of Additive Manufacturing Letters.
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