AMP_04_May_June_2021_Digital_Edition

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 | M A Y / J U N E 2 0 2 1 8 0 3D PRINTSHOP Ultrasound and computer algorithms control howmaterial settles into shape. Courtesy of University of Bath. SONOLITHOGRAPHY: 3D PRINTING WITH SOUND Scientists from the Universities of Bath and Bristol have shown that it’s possible to create precise, predeter- mined patterns on surfaces from aero- sol droplets or particles, using comput- er-controlled ultrasound in a technique called “sonolithography.” Dr. Jenna Shapiro, research as- sociate at the University of Bristol says “Sonolithography enables gentle, non- contact, and rapid patterning of cells and biomaterials on surfaces. Tissue engineering can use biofabrication methods to build defined structures of cells and materials.” “The objects we are manipulating are the size of water drops in clouds,” says professor Bruce Drinkwater, Uni- versity of Bristol. “It’s incredibly excit- ing to be able to move such small things with such fine control. This could allow us to direct aerosol sprays with unheard of precision, with applications such as drug delivery or wound healing.” Beyond its applications in bio- medicine, the team has shown the technique to be applicable to a variety of materials. Printed electronics is an- other area the team is keen to devel- op, with sonolithography being used to arrange conductive inks into circuits and components. GRAPHENE AEROGELS FOR SCALABLE WATER TREATMENT In a recent study, engineers from the University at Buffalo, New York, describe a new process of 3D printing graphene aerogels that they say is scal- able and creates a version of the materi- al that’s stable enough for repeated use in water treatment. “The goal is to safely remove con- taminants from water without releas- ing any problematic chemical residue,” says study co-author Nirupam Aich, assistant professor of environmental engineering. “The aerogels we’ve cre- ated hold their structure when put in water treatment systems, and they can be applied in diverse water treatment applications.” wastewater treatment plants, he says. He adds the aerogels can be removed from water and reused in other loca- tions, and that they don’t leave any kind of residue in the water. MOLYBDENUM METAL MATRIX COMPOSITE POWDER Scientists at Oak Ridge National Laboratory have demonstrated that molybdenum titanium carbide, a re- fractory metal alloy that can withstand extreme temperature environments, can also be crack free and dense when produced with electron beam pow- der bed fusion. This finding indicates the material’s viability in additive manufacturing. Molybdenum and its associated alloys are difficult to process through traditional manufacturing because of their high melting temperature, reac- tivity with oxygen, and brittleness. To address these shortcomings, the team formed a Mo metal matrix composite by mixing molybdenum and titanium car- bide powders. “Our results showed that fabrica- tion from a mechanically alloyed metal matrix composite powder is feasible,” ORNL’s Mike Kirka says. “The structures formed by the fused powders can with- stand high temperatures, indicating that molybdenum and its alloys can be used for aerospace and energy conver- sion applications.” Crack free, dense refractory metal molybdenum for additive manufacturing. Courtesy of ORNL/U.S. Dept. of Energy. At left, a 3D printer creates the hexagonal- shaped graphene aerogel sheet. At right, the aerogel (now black) filters dirty water. Courtesy of Environmental Science: Nano. In tests, the reconfigured aerogel removed certain heavy metals, such as lead and chromium, that plague drink- ing water systems nationwide. It also removed organic dyes, such as cationic methylene blue and anionic Evans blue, as well as organic solvents like hexane, heptane, and toluene. The aerogels can also be scaled up in size, Aich says, because unlike nanosheets, aerogels can be printed in larger sizes. This eliminates a previous problem inherent in large-scale pro- duction and makes the process avail- able for use in large facilities, such as in