March_2022_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 | M A R C H 2 0 2 2 7 PROCESS TECHNOLOGY PROGRAMMING MORPHABLE MATERIALS Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), Boston, developed a platform that uses ma- chine learning to program the transfor- mation of 2D stretchable surfaces into specific 3D shapes. The team began by dividing an in- flatable membrane into a 10 x 10 grid of 100 square pixels that can either be soft or stiff. The soft or stiff pixels can be combined in an almost infinite va- riety of configurations, making manu- al programming extremely difficult. To meet the challenge, researchers used finite element simulations to sample the infinite design space. Next, neu- ral networks used that sample to learn how the location of soft and stiff pixels controls the deformation of the mem- brane when pressurized. Then, they used the new design method to build Researchers aimed at upcycling a commodity thermoplastic, polysty- rene-b-poly(ethylene-co-butylene)- b-polystyrene, or SEBS, a rubbery poly- mer material that is easy to process but not engineered for tough adhesion. The team modified SEBS’ chemical struc- ture with dynamic crosslinking to make it more robust, as well as to create re- use pathways for plastics—beyond tra- ditional recycling—that enhance their performance for new applications. Results showed crosslinked bonds shift within the material to enable spe- cific properties and adhere to surfaces so strongly that a thin square centime- ter can hold roughly 300 pounds. The material was so tough in adhering to glass, in fact, that glass fractured be- fore the sample debonded. The ap- proach also enhanced thermal stabili- ty to 400°F, making the adhesive attrac- tive for ambient and high-temperature applications. The development wid- ens applications for aerospace, auto- motive, and construction adhesives. energy.gov. Regular grid (left) divides a membrane’s domain into soft (blue) or stiff (purple) pixels; membrane (center) is fabricated as a continuous, flat material; after inflation, complex deformation (right) reflects stiff and soft pixels. Courtesy of Bertoldi Lab/Harvard SEAS. and test a device for mechanotherapy that can stimulate tissue around a scar to enhance healing and reduce recov- ery time. The platform can be used to design morphable surfaces at multiple scales for applications frommedical de- vices to architecture. harvard.edu . UPCYCLED PLASTIC ADHESIVES Using polymer chemistry, re- searchers at the DOE’s Oak Ridge Na- tional Lab transformed a common household plastic into a reusable adhe- sive with a rare combination of strength and ductility. The new adhesive is one of the toughest materials ever report- ed, and the work advances pathways to design a new class of tough adhesives with desirable features merged into a single material. The technology adapts to bear heavy loads, tolerate extreme stress and heat, and reversibly bond to various surfaces including glass, alumi- num, and steel. BRIEF As part of a new merchant machining program for the aerospace industry, Guill Tool & Engineering, West Warwick, R.I., offers 5-axis machining centers, high precision machining, and full wire EDM capabilities including a 0.008-in. hole popper. Typical products include brackets, latches, engine components, fine hole cooling channels, and structural mechanisms. guill.com/aerospace. A common plastic was upcycled to develop a novel reusable adhesive. Courtesy of Carlos Jones/ORNL, U.S. DOE.