|go to week of Jan 27, 2013||27||28||29||30||31||1||2|
|go to week of Feb 3, 2013||3||4||5||6||7||8||9|
|go to week of Feb 10, 2013||10||11||12||13||14||15||16|
|go to week of Feb 17, 2013||17||18||19||20||21||22||23|
|go to week of Feb 24, 2013||24||25||26||27||28||1||2|
Abstract: While carbon nanotubes (CNTs) are known for their outstanding properties, manufacturing of large scale assemblies of CNTs with compelling performance is challenging due to limited understanding and control of the CNT network density and order. I will present two new manufacturing processes to build higher-order CNT assemblies, using vertically aligned (VA) CNT forests as a starting point. Both processes rely on understanding the structure-mechanics relationship in CNT forests and the interaction of CNTs with liquids. The first technique, called capillary forming, enables the integration of VA-CNT in applications ranging from microsystems to micro-architectured composites. Capillary forming results from shape-directed capillary rise during solvent condensation; followed by evaporation-induced shrinkage of as-grown CNTs. The heterogeneous strain evolution during the liquid-solid interface shrinkage cause 3-D geometric transformations of CNTs. Guided by modelling and in situ experimentation, a portfolio of CNT micro-architectures including straight, bent, folded and helical profiles, are fabricated demonstrating superior mechanical and electrical properties to microfabrication polymers (5 GPa modulus and 104 S/m conductivity).
Second, in pursuit of new multifunctional lightweight composites, continuous CNT yarns and sheets are produced by mechanical rolling and capillary assisted joining. The yarns' mechanical stiffness, strength and electrical conductivity can be tuned by engineering the morphology of CNT network. This process is understood via analytical modeling, mechanical testing, and in situ X-ray structural characterization of CNT joints. Building upon these insights, I finally propose new scalable manufacturing processes for multifunctional yarns and surfaces from silicon, ceramic and metal nanofilaments.
Bio: Sameh Tawfick is a Postdoctoral Associate in the Laboratory for Manufacturing and Productivity at the Massachusetts Institute of technology. He obtained his PhD from the University of Michigan (advised by Prof. John Hart), and his M.Sc. and B.M.E. from Cairo University, Egypt, all in Mechanical Engineering. Sameh spent several years in industry in Egypt and Switzerland, where his experience spanned the design and manufacturing of pharmaceutical reactors to the maintenance of gas turbines. During his PhD he obtained the Robert M. Caddell Memorial Award for outstanding research in manufacturing, the Azarkhin and the Ivor K. McIvor Awards for outstanding research in applied mechanics, and the Rackham Predoctoral Fellowship. In his research, Sameh applies machine design, nanomaterial synthesis and characterization towards the manufacturing of multifunctional surfaces and structural composites from small building blocks.