November 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 | N O V E M B E R / D E C E M B E R 2 0 1 9 7 SELF-SHARPENING SEA URCHINS In the middle of their spiked bod- ies, pink sea urchins have five teeth— each one held by its own circular jaw. A team of researchers at Northwestern University, Evanston, Ill., has discov- ered how these fangs sharpen them- selves. Instead of simply resisting wear, the teeth are built to chip in a way that helps them maintain a sharp edge. To make up for the loss of material, an ur- chin’s teeth continue to grow through- out life. Scientists have long thought that sea urchins might have a sharp- ening mechanism, but it was not clear how they could selectively cleave por- tions of their teeth to stay sharp. In the new study, researcher Hora- cio Espinosa and his colleagues com- bined sophisticated mechanical testing and electron microscopy to capture 3D movies showing how the urchin’s dental structures wear. Their studies show that the teeth consist of ceramic compos- ites arranged in a precise way. On the convex side of the tooth, calcite fibers provide structural integrity. This fibrous composite transitions to another com- posite made of inclined calcite plates. As the tooth wears, those calcite plates chip away tomaintain sharpness. These results could help guide the design of both microstructure and materials for OMG! OUTRAGEOUS MATERIALS GOODNESS tools used in a wide range of cutting, grinding, and boring applications. cell. com/matter. REACTIVE POLYMER AM SYSTEM Magnum Venus Products (MVP), Knoxville, Tenn., recently collaborated with Polynt, Italy, and the DOE’s Oak Ridge National Laboratory (ORNL) to deploy the first large-scale reactive polymer additive manufacturing (AM) systemcommercially available to indus- try. MVP’s reactive additive manufactur- ing (RAM) machine, first announced in March, and Polynt’s reactive additive deposition material (PRD 1520) are working together to enable fabrication of thermoset materials at a larger scale than previously possible. The thermo- set advantage stems from the ability to cross-link polymers between printed layers resulting in stronger, more ther- mo-tolerant products. By collaborating with ORNL, MVP was able to scale up the technology from a benchtop solu- tion to a commercially ready machine. PRD 1520 is a specially formulated reac- tive monomer material developed for use in the RAM machine. The material offers superior interlaminar adhesion, exceptional machinability, and a high heat distortion temperature compatible with aerospace grade tooling applica- tions. mvpind.com. Five sea urchin tooth tips stacked on top of each other within the jaws. Courtesy of Horacio Espinosa. RAM is the only large-scale thermoset AMmachine enabling 3D printing of thermoset materials for prototype and production parts. Artist’s impression of a single-nanowire spectrometer. Courtesy of Ella Maru Studio. SINGLE-NANOWIRE SPECTROMETER Scientists at the University of Cam- bridge, U.K., designed an ultra-minia- turized device that could image single cells without the need for a microscope or make chemical fingerprint analysis possible with a smartphone camera. Made of a single nanowire, the new de- vice is the smallest spectrometer ever created. Most modern spectrometers are bulky, and are based around prin- ciples similar to what Isaac Newton first demonstrated with his prism in the 1600s—the spatial separation of light into different spectral components. Researchers have now produced a system up to 1000 times smaller than those previously reported. The Cam- bridge team, working with colleagues from the U.K., China, and Finland, used a nanowire whose material composi- tion is varied along its length, enabling it to respond to different colors of light across the visible spectrum. Using techniques similar to those employed for making computer chips, they then created a series of light-responsive sec- tions on the nanowire. The team hopes the tiny platform will lead to a new gen- eration of ultra-compact spectrome- ters. www.cam.ac.uk .