Bio Focus
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Bio Focus 3D printed scaffolds developed from isomalt sweetener
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hree-dimensional (3D) printing is one of the fastest-growing industrial technologies, but it still lacks versatility. Commercial 3D printers typically use brittle plastics that have limited biocompatibility and cannot print hollow or unsupported structures. Now, a group of researchers from the University of Illinois at Urbana-Champaign has developed a way to 3D-print open structures using an artificial sweetener called isomalt. This
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response to hydrated, two-dimensional tungsten oxide (WO3·2H2O) electrodes that contain water. They reported their findings in a recent issue of ACS Nano (doi: 10.1021/acsnano.8b02273). “The exciting aspect about the correlation between the electrochemical current and electrode deformation measured via AFM is that it allows us to probe electro-chemo-mechanics at the nanoscale,” Augustyn says. “This was particularly helpful in elucidating the unexpected role of water incorporated into the structure of the hydrated form of tungsten oxide.” “We found that the water layers in hydrated tungsten oxide do two things,” says Ruocun Wang, a doctoral student in Augustyn’s laboratory and lead author of the article. “First, they minimize deformation and reduce expansion and contraction of the material as ions move in and out. Second, the water layers make the deformation more reversible, meaning that the material returns to its original dimensions more easily,” he says. The researchers used a platinum-coated AFM cantilever to measure deformations in tungsten oxide electrodes while they applied an electrochemical cycling experiment with a sulfuric acid electrolyte. The shapes of charge–discharge cyclic voltammetry curves corresponded with the mechanical deformation rate of the respective electrodes. Of note, electrochemical results contrasted the pseudocapacitive-like behavior of hydrated WO3 (fast, reversible surface reactions) against
Scanning probe microscopy captures the flexibility of tungsten oxide electrodes during electrochemical cycling and highlights the relative ease with which ions enter and exit the hydrated electrode form (a) compared to the anhydrous electrode (b). Credit: Veronica Augustyn et al.
the battery-like intercalation process in its anhydrous counterpart (slow, diffusionlimited process). Anhydrous tungsten oxide experienced significant strain in order to intercalate the protons into its structure, and the asymmetrical profile of its charge– discharge cycling behavior mirrored its AFM-detected mechanical deformation rate. Structural analysis of the hydrated material showed that water molecules in the interlayer spacing separated the layers of corner-sharing WO5(OH2) octahedra and confined the deformation to two dimensions. This, in turn, endowed the hydrated form with greater flexibility and allowed ions to easily move in and out of the electrodes during cycling.
Albert Davydov of the National Institute of Standards and Technology, who was not involved in this
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