Northwestern University researchers have developed a stereolithographic 3D printer that can print an object the size of an adult human in just a couple of hours. Called HARP for high-area rapid printing, this printer uses a patent-pending version of stereolithography that circulates liquid plastic to remove heat, which can cause printed parts to crack and deform. To dissipate the heat that is generated from the polymerization of the resin, HARP prints vertically and uses a nonstick liquid that behaves like Teflon. The printer projects ultraviolet light through a window to solidify resin on top of a vertically moving plate. The “liquid Teflon” flows over the window to remove the heat and then circulates it through a cooling unit. “Our technology generates heat just like the others, but we have an interface that removes the heat,” professor Chad Mirkin said. High-area rapid printing technology prints vertically, using ultraviolet light to cure liquid resin into hardened plastic. Courtesy of Northwestern University. Researcher James Hedrick said that because the interface is nonstick, it prevents the resin from adhering to the printer. “This increases the printer’s speed by a hundredfold because the parts do not have to be repeatedly cleaved from the bottom of the print-vat,” Hedrick said. According to its creators, HARP will be able to handle large-batch production and production of large and small parts. “When you can print fast and large, it can really change the way we think about manufacturing,” Mirkin said. “With HARP, you can build anything you want without molds and without a warehouse full of parts. You can print anything you can imagine on demand.” HARP uses high-resolution light-patterning to achieve ready-to-use parts without extensive post-processing. HARP is the biggest 3D printer to date. Its size allows it to print a large, continuous structure or many different small structures at once. Courtesy of Northwestern University. The prototype HARP technology is 13-ft tall with a 2.5-sq-ft print bed and can print about half a yard in an hour. The researchers demonstrated continuous vertical print rates exceeding 430 mm per hour with a volumetric throughput of 100 liters per hour and printed proof-of-concept structures from hard plastics, ceramic precursors, and elastomers. The team believes the new printer will be commercially available in the next 18 months. It could be used to print parts for medical devices, cars, airplanes, construction, and other fields. The research was published in Science (https://doi.org/10.1126/science.aax1562). Watch HARP in action as it vertically and continuously prints a large 3D object. Courtesy of Northwestern University.