Although metallic glasses can have exceptional strength, they tend to fracture in an apparently brittle manner (even though there is extensive microscopic deformation). For this reason, there is great interest in making composite materials that have the high strength of metallic glasses yet fail in a more graceful manner. One approach to making a composite is to include particles of a soft, ductile metal in a metallic glass matrix. Plastic deformation of the particles induces stresses in the matrix. The figure is a contour plot of these stresses, obtained from a finite element model of the deformation of the composite. The round region near the center is a particle; the red contours around the particle indicate places where the metallic glass matrix can deform by shear band formation. Because deformation is restricted to the region near the particles, and because there are many such particles, the composite can show significantly greater plasticity than an unreinforced metallic glass.
Primary rat hepatocytes self-assemble into multi-cellular spheroids and maintain differentiated functions when cultured on a two-dimensional (2-D) substrate conjugated with galactose ligand (A & B). C & D show a hepatocyte spheroid formed on a porous functional fibrous scaffold. This scaffold comprises of fibers with an average diameter of 760 nm prepared by electrospinning of poly(e-caprolactone-co-ethyl ethylene phosphate) (PCLEEP). We have immobilized a hepatocyte-specific ligand, galactose, onto the surface of these submicron fibers at a high density to facilitate hepatocyte adhesion. This functional scaffold supports functional maintenance of hepatocytes and promotes the formation of an integrated spheroid-fiber construct. -in collaboration with Prof. Kam Leong at Department of Biomedical Engineering and Division of Johns Hopkins in Singapore. |
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