January_2021_AMP_Digital

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 1 1 3 NEW RESINS FOR 3D PRINTING Improving upon previous ground- breaking work, scientists at Lawrence Livermore National Laboratory (LLNL), Calif., have achieved a “significant ad- vancement” for volumetric additive manufacturing (VAM), greatly expand- ing the range of material properties achievable with the technique. Re- searchers adapted a new class of ma- terials, called thiol-ene resins, for their proprietary method that produces ob- jects nearly instantly. The newmaterials have shown promise for applications in- cluding adhesives and electronics, and as biomaterials, the researchers say. The resins can be used with LLNL’s volumetric printing techniques, includ- ing Computed Axial Lithography (CAL), which produces objects by projecting beams of 3D-patterned light into a vial of resin. The vial then spins as the light cures the liquid resin into a solid at the desired points in the volume, and the uncured resin is drained, leaving the 3D object behind in a mat- ter of seconds. Previously, researchers worked with acrylate-based resins that produced brittle and easily breakable objects using the CAL process. With thiol-ene resins, researchers were able to build tough, strong, as well as stretchable and flexible objects using a cus- tom VAM printer at LLNL. “These results are a key step to- ward our vision of using the VAM par- adigm to significantly expand the types of materials that can be used in light-driven 3D printing,” the research- ers explain. llnl.gov. SMART WINDOWS A collaborative research team from Pohang University of Science & Technology (POSTECH), South Korea, developed new source technology for smart windows that change colors according to the amount of moisture, without needing elec- tricity. They success- fully created a variable color filter with ametal- hydrogel-metal reso- nator structure using a chitosan-based hy- drogel and combined it with solar cells to make EMERGING TECHNOLOGY The National Science Foundation awarded the Cornell High Energy Synchrotron Source $32.6 million to build a High Magnetic Field beamline, which will allow researchers to conduct precision x-ray studies of materials in persistent magnetic fields that exceed those available at any other synchrotron. cornell.edu . BRIEF a self-powering humidity sensor. The team found that when the chitosan hydrogel is made into a metal- hydrogel-metal metamaterial, the res- onance wavelength of light transmit- ted changes in real time depending on the humidity of the environment. This is because the chitosan hydrogel repeats expansion and contraction as the humidity changes around it. Using this mechanism, the team developed a humidity sensor that can convert light’s energy into electricity by combining a solar battery with a water variable wavelength filter made of the meta- material. “This sensing technology can be used in places like nuclear power reac- tors where people and electricity can- not reach,” the researchers say. “It will create even greater synergy if combined with IoT technology such as humidity sensors that activate or smart windows that change colors according to the lev- el of external humidity.” international. postech.ac.kr. Depiction of a metal-hydrogel-metal filter structure that repeats expansion and contractions as moisture level changes around it. Courtesy of POSTECH. Example of a tough, strong, stretchable, and flexible object created through custom VAM at Lawrence Liver- more. Courtesy of MaximShuste /LLNL.