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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 2 0 4 8 3D PRINTSHOP A new technique uses UV light to fortify 3D-printed materials. Courtesy of University of Tennessee at Knoxville. UV LIGHT STRENGTHENS 3D-PRINTED MATERIALS Based on UV radiation, a new process developed by scientists at the University of Tennessee at Knoxville (UT) and Oak Ridge National Laborato- ry (ORNL) could strengthen the bonds of 3D-printed materials to withstand 200% more transverse stress. “There are about a half dozen methods of 3D printing, and a lack of layer adhesion is a problem in all of them. This means that many of these materials are brittle, so they can’t handle much strain before they break,” says UT chemistry profes- sor Mark Dadmun. Dadmun and his team became intrigued by this problem when a 3D-printed car was produced at ORNL. “While this was an amazing accom- plishment, those cars are not actually drivable because they have weakness- es. If there were ever a crash, these cars would splinter,” says Dadmun. This lack of strength is the result of poor layer ad- hesion due to the bulky nature andmin- imized interactions of polymer chains between layers. Dadmun had an idea to solve this problem. “We found that making chemical bonds across the layers of a printed product would strengthen the item, because the molecules are now bonded together rather than being in layers where the molecules are just float- ing by each other,” he ex- plains. In the new process, chemical bonds are formed when UV light is applied during printing. The light starts a reaction that bonds the printing material, thus creating stronger products. The method is easily imple- mented and offers improve- ments in fused deposition modeling for multiple poly- mer materials. utk.edu. 3D-PRINTED SURFACES CLEAN THEMSELVES At the University of Cordoba, Spain, the manufacturing processes engineer- ing group recently studied how to op- timize the features of 3D-printed sur- faces—including the ability to clean themselves. Such surfaces are helpful in numerous applications including traffic signals, a sector in which 3D printing is already being used to print self-clean- ing bulbs. The new study analyzed the roughness characteristics of 3D-printed surfaces. The goal is to make surfaces with few raised parts and a good finish, in order to avoid dust from becoming embedded and making it easy for dirt particles to fall off. 3D printers have several opera- tional parameters that can be used to modify the surface characteristics of printed components. To create models using data mining techniques, the team analyzed the printing parameters that most influence a surface’s self-clean- ing ability. The study was carried out in partnership with Casado Stamping, a company in Cordoba that manufac- tures and performs maintenance on traffic signals. Smart Materials 3D, a nearby manufacturer that makes ther- moplastic filaments used as raw ma- terial in 3D printers, also participated. The team’s next project aims to improve the surface properties of 3D-printed molds used to manufacture polyure- thane foam pieces, such as car seats, mattresses, and pillows. www.uco.es . ADDITIVE METHOD SUITS BIOMATERIALS A new method developed by re- searchers at the University of Birming- ham, U.K., could be used to print soft biomaterials that would repair defects in the human body. Printing soft ma- terials using additive manufacturing has been challenging because if the structures are not supported, they sag and lose their shape. The new tech- nique, called suspended layer additive manufacturing, uses a polymer-based hydrogel in which the particles have been manipulated to create a self-heal- ing gel. Liquids or gels can be injected directly into this medium and built up in layers to create a 3D shape. The new hydrogel shows potential for mak- ing replacement biomaterials such as heart valves or blood vessels, or for bio- compatible plugs that can be used to treat bone and cartilage damage. www. birmingham.ac.uk. Juan Manuel Barrios and Pablo Romero are working on 3D-printed surfaces that keep themselves clean. Courtesy of University of Cordoba.