Gecko-Inspired Biocidal Organic Nanocrystals Initiated from a Pencil-Drawn Graphite Template

The biocidal properties of gecko skin and cicada wings have inspired the synthesis of synthetic surfaces decorated with high aspect ratio nanostructures that inactivate microorganisms. Here, we investigate the bactericidal activity of oriented zinc phthalocyanine (ZnPc) nanopillars grown using a simple pencil-drawn graphite templating technique. By varying the evaporation time, nanopillars initiated from graphite that was scribbled using a pencil onto silicon substrates were optimized to yield a high inactivation of the Gram-negative bacteria, Escherichia coli. We next adapted the procedure so that analogous nanopillars could be grown from pencil-drawn graphite scribbled onto stainless steel, flexible polyimide foil, and glass substrates. Time-dependent bacterial cytotoxicity studies indicate that the oriented nanopillars grown on all four substrates inactivated up to 97% of the E. coli quickly, in 15 min or less. These results suggest that organic nanostructures, which can be easily grown on a broad range of substrates hold potential as a new class of biocidal surfaces that kill microbes quickly and potentially, without spreading antibiotic-resistance genes

Energy dissipation in shape memory zirconia particles, packings, and composites

Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 47-49).This research project lies at the intersection of two classes of materials, namely superelastic materials and granular materials, each known for their ability to dissipate large amounts of kinetic energy. Because of their energy-absorbing properties, superelastic granular materials are of interest for development into applications involving force protection. Quasi-static, closed-die compression tests were conducted on granular packings of ceria-doped zirconia, a material which is well-known to exhibit shape memory and superelastic behavior. The doping level of ceria in the zirconia system was controlled to experimentally determine the mole percent for optimal energy dissipation in a granular packing. Various particle size distributions were selected to study mechanisms of energy dissipation in a granular packing including particle friction, fracture, and martensitic phase transformation. To study the behavior of encapsulated shape memory and superelastic zirconia particles, composites were fabricated using polyurea as a matrix material, and the bonding between the zirconia particles and polyurea matrix was studied along with mechanical properties. Finally, the effect of high strain rate impact was observed on ceria-doped zirconia pellets using laser induced particle impact testing (LIPIT) which launches single, micron-sized particles at high velocities. This thesis provides further insight into the mechanical behavior of granular superelastic ceramics under different constraints and loading conditions while optimizing for energy dissipation.by Victor K. Champagne III.S.M.S.M. Massachusetts Institute of Technology, Department of Materials Science and Engineerin

CD8+ T cell efficacy in vaccination and disease

Much effort has been devoted to the design of vaccines that induce adaptive cellular immunity, in particular CD8+ T cells, which have a central role in the host response to viral infections and cancers. To date, however, the development of effective T cell vaccines remains elusive. This is due, in part, to the lack of clearly defined correlates of protection and the inherent difficulties that hinder full characterization of the determinants of successful T cell immunity in humans. Recent data from the disparate fields of infectious disease and tumor immunology have converged, with an emphasis on the functional attributes of individual antigen-specific T cell clonotypes, to provide a better understanding of CD8+ T cell efficacy. This new knowledge paves the way to the design of more effective T cell vaccines and highlights the importance of comprehensive immunomonitoring