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 / F E B R U A R Y 2 0 2 3 5 2 3D PRINTSHOP 3D-printed prototype could help repel insects. Courtesy of Fanfan Du, Uni Halle. WEARABLE JEWELRY-LIKE INSECT REPELLENT Rings and other wearable shapes made with insect repellent have been 3D printed by researchers at Martin Luther University Halle-Wittenberg (MLU). The active ingredient is first “encapsulated” and formed into the desired shape, such as a ring, which can then be worn. It releases an agent designed to repel mosquitoes for a long time. The researchers have developed their prototypes using IR3535, an insect repellent developed by Merck. “Mosquito sprays containing IR3535 are very gentle on the skin and have been used all over the world for many years,” says Professor René Androsch from the MLU. The researchers have succeeded in using a special 3D printing technique to insert the insect repellent into a biodegradable polymer in a controlled manner and to shape the mixture of substances in various ways. “The basic idea is that the insect repellent continuously evaporates and forms a barrier for insects,” explains the lead author of the study, Fanfan Du, a doctoral candidate at the MLU. The rate at which the insect repellent evaporates depends on many different factors, including temperature, concentration and the structure of the polymer used. After conducting various experiments and simulations, the team predicts that the insect repellent needs well over a week to evaporate completely at a temperature of 37°C (body temperature). www.uni-halle.de. METAL NANOCLUSTERS KEEP MATERIAL STRONG AND LIGHT A new material developed at Stanford University is able to absorb twice as much energy than other 3D-printed materials of a comparable density. The material prints miniscule lattices that are both strong and light and could be used to create better lightweight protection for fragile pieces of satellites, drones, andmicroelectronics. Wendy Gu, an assistant professor of mechanical engineering and her colleagues incorporated metal nanoclusters—tiny clumps of atoms—into their printing medium and using two-photon lithography, where the printing material is hardened through a chemical reaction initiated by laser light. They found that their nanoclusters were very good at jump-starting this reaction and resulted in a material that was a composite of the polymer printing medium and metal. The researchers were able to combine metal nanoclusters with acrylates, epoxies, and proteins, several common classes of polymers that are used in 3D printing. Moreover, the nanoclusters helped to speed up the printing process. By combining the nanoclusters with proteins, for example, Gu and her colleagues were able to print at a rate of 100 mm/s, which is about 100 times faster than had previously been achieved in nanoscale protein printing. The researchers tested their new material with several different lattice structures, prioritizing the ability to carry a heavy load in some and the ability to absorb an impact in others. With the nanocluster-polymer composite, all the structures demonstrated an impressive combination of energy absorption, strength,andrecoverability. “The lattice structure certainly matters, but what we’re showing here is that if the material it’s made out of is optimized, that’s more important for performance,” Gu says. “You don’t have to worry about exactly what the 3D structure is if you have the right materials to print with.” stanford.edu. Tiny but strong Stanford logo made using nanoscale 3D printing. Courtesy of John Kulikowski. Printer.HM is an open design, multifunctional 3D printer for liquidous and soft materials. This multi-printhead system—built on a hackable robotic arm and offering multi-functionalities in one platform via heating and ultraviolet modules—was developed by researchers from the Department of Engineering, University of Cambridge, and The Nanoscience Center, University of Cambridge, in collaboration with the Universities of Macau and Oxford. In addition to offering good print compatibility, the printer can be used for liquid dispensing, multimaterial printing, printing with variable speed, embedded printing (creating freeform and overhanging structures), non-planar printing, and pick-and-place applications. www.cam.ac.uk. BRIEF
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