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Photochromic materials are of great interest due to their applications in ophthalmic lenses, display and communications systems, and optical storage and memory devices. The coupling of changes in electronic state accompanying photoisomerization with other physical phenomena would allow development of advanced functional materials for smart surfaces, spintronics, and optoelectronics. Metal coordination of photochromes provides a novel and potentially powerful approach to the development of systems in which changes in electronic state of the photochrome can induce changes in redox, magnetic, or optical properties of the metal center. This approach, however, has been largely unexplored. Toward this end, we have investigated a unique set of photochromic metal complexes formed by incorporating photochromic spirooxazines into magnetically interesting inorganic motifs. The complexes retain their photochromic activity, and in some cases exhibit charge transfer induced spin state changes in both solution and solid states. The kinetics of light-induced switching and thermal relaxation between redox and spin states is dictated by the photochromic ligand, and the first /direct observation/ of room temperature photomagnetism in a molecular material will be discussed.

With rapid advances in both biological and physical sciences, there exist unprecedented opportunities and promises at the interface between mechanics and cellular/molecular biology, as novel materials fabrication, characterization, testing, and multiscale simulation and modeling tools and techniques are being used to address urgent issues in biology, medicine, engineering, and society. This talk will discuss some recent studies on cell-materials interactions, including the mechanics of cellular uptake of nanoparticles by receptor-mediated endocytosis and coarse-grained molecular dynamics methods capable of detailed molecular mechanics simulations of complete lipid bilayer segments interacting with nanoparticles, as well as stochastic-elastic modeling of cell-matrix interaction. The discussions will be organized around the following questions: Why and how does cellular uptake of nanoparticles depend on the particle size, shape, aspect ratio and elasticity? Why is there a micron-scale size limit on focal adhesions in cell-matrix interaction? Why do many cells prefer stiffer substrates? Why is there an optimal stiffness of substrate for cell motility? With these questions in mind, the talk will discuss mechanisms by which nanoparticles can enter cells, and how cells can sense mechanical properties of their surroundings and actively control adhesion and deadhesion via cytoskeletal contractile machinery.

About Prof. Huajian Gao

Huajian Gao received his B.S. degree from Xian Jiaotong University of China in 1982, and his M.S. and Ph.D. degrees in Engineering Science from Harvard University in 1984 and 1988, respectively. He served on the faculty of Stanford University between 1988 and 2002, where he was promoted to Associate Professor with tenure in 1994 and to Full Professor in 2000. He served as a Director at the Max Planck Institute for Metals Research between 2001 and 2006 before joining the Faculty of Brown University in 2006. At present, he is the Walter H. Annenberg Professor of Engineering at Brown. Professor Gao’s research is focused on the understanding of basic principles that control mechanical properties and behaviors of materials in both engineering and biology. He is an author/co-author of more than 300 scientific papers with total citations exceeding 11K and an h-index of 56. He is a Member of U.S. National Academy of Engineering and co-editor-in-Chief of the Journal of the Mechanics and Physics of Solids (2006), the flagship journal of his field. He is also the recipient of numerous academic honors, from a John Simon Guggenheim Fellowship in 1995 to recent honors including the Humboldt Research Award from Germany and Rodney Hill Prize in Solid Mechanics from the International Union of Theoretical and Applied Mechanics in 2012.

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