May_June_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 Y / J U N E 2 0 2 2 5 TASTY TURMERIC FORTIFIES FUEL CELLS A team from Clemson University’s Nanomaterials Institute (CNI), South Carolina, and Sri Sathya Sai Institute of Higher Learning in India found a way to combine curcumin, the substance in turmeric, with gold nanoparticles to create an electrode that requires significantly less energy to convert ethanol into electricity versus other methods. Although more testing is needed, the discovery is another step toward replacing hydrogen as a fuel cell feedstock. The team focused on the fuel cell’s anode, where the ethanol is oxidized, and selected gold as the catalyst. Rather than using conducting polymers or metal-organic frameworks to deposit gold on the electrode’s surface, researchers used curcumin due to its structural uniqueness. Curcumin is applied to decorate the gold nanoparticles in order to stabilize them, forming a porous network around them. The team RESEARCH TRACKS deposited the curcumin gold nanoparticles on the surface of the electrode at 100x lower electric current than in previous studies. “Without this curcumin coating, the performance is poor,” says Apparao Rao, CNI’s founding director. “We need this coating to stabilize and create a porous environment around the nanoparticles, and then they do a super job with alcohol oxidation. The next step is to scale the process up and work with an industrial collaborator who can actually make the fuel cells and build stacks of fuel cells for real applications.” clemson.edu. SUPER SPEEDY GLASS PRINTING Researchers at Lawrence Livermore National Laboratory (LLNL) and the University of California, Berkeley are using a new 3D printing method to make microscopic objects out of silica glass in mere seconds. The process employs a laser-based volumetric additive manufacturing (VAM) approach, an emerging technology in near-instant 3D printing. The computed axial lithography (CAL) technology developed by LLNL and UC Berkeley is similar to computed tomography imaging. CAL works by computing projections from several angles through a digital model of a target object, optimizing these projections, and then delivering them into a rotating volume of photosensitive resin using a digital light projector. Over time, the projected light patterns reconstruct a 3D light dose distribution in the material, curing the object at points exceeding a light threshold while the vat of resin spins. After the fully formed object materializes, the vat is drained to retrieve the part. The process combines a microscale VAM technique called micro-CAL, which uses a laser instead of an LED source, with a nanocomposite glass resin developed by the German Alcohol, shown as green droplets (top), interacts with curcumin-enveloped gold nanoparticles to efficiently yield energy, depicted as white sparks (bottom). company Glassomer and the University of Freiburg. Using the new approach, the team created glass objects with complex microstructures, exhibiting a surface roughness of just 6 nm and features down to 50 μm. Researchers say the benefit of VAM for micro-optics is that it can produce extremely smooth surfaces without layering artifacts, resulting in faster printing without additional post-processing time. Applications could include micro-optics in high-quality cameras, consumer electronics, biomedical imaging, chemical sensors, virtual reality headsets, advanced microscopes, microfluidics with challenging 3D geometries, and more. Caitlyn Cook, a polymer engineer in LLNL’s materials engineering division, says she and her team will further tune the resolution of VAM and the doses required for a variable range of resolutions and print speeds. In addition, the team is conducting a feasibility study to advance the VAM glass printing efforts for larger optics. “Cracking problems typically arise in larger prints due to shrinkage stresses,” says Cook. “Our teams at LLNL are developing custom formulations to produce larger optics and glass printed parts that will not crack during the debinding and sintering processes.” llnl.com. Microscopic object made of silica glass using volumetric additive manufacturing.

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