Conferences, Lectures, & Seminars
Events for April
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Electronically tunable nanomaterials
Wed, Apr 02, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Horst HahnForschungszentrum KarlsruheInstitute for Nanotechnology and Joint ResearchLaboratory NanomaterialsTechnische Universität DarmstadtAbstract:The properties of materials are typically controlled in a static manner by the microstructure. This implies control of the grain size, defect concentration, structure and metastability. As long as the microstructure does not change during the use of the material, the properties of the material are fixed, or irreversible. In contrast, in semiconducting materials, properties can be tuned by the application of an external field due to the space charge regions which extend far from the interfaces. In metallic systems, this effect cannot be observed unless the dimensions of the structures are in the nanometer regime. The reason for this different behaviour is the small spatial dimension of the space charge regions due to the effective screening of the induced charges by the conduction electrons.
In nanoporous metals and thin films exposed to appropriate electrolytes, it has been demonstrated that substantial changes of physical properties can be induced by the application of a potential between the nanostructured metal and a counter electrode. Examples of the changes of surface stresses and the electrical resistivity of thin Gold films and nanoporous Gold will be presented. A simple model is proposed based on the modification of the electron density distribution at the interface of the metal and the electrolyte. Effectively, the corresponding change of the effective thickness of the sample is the major cause of the observed resistivity change.
Additionally, a transparent conducting oxide, ITO, in a nanoparticulate form has been prepared from a dispersion using spin coating. The observed resistivity changes, i.e. the on/off ration can be as large as 2.000, i.e. 200.000 %, between the different values of the control potential. Moreover, the device exhibits field effect transistor behavior identical to a conventional semiconductor, but in this case observed in a material with a large charge carrier density exhibiting metallic conduction behaviour. Additionally, the mobility is exceeding 20 cm2/Vs. The device can be used for printable electronics and transparent electronics.
Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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NanoRobotic Systems
Wed, Apr 09, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Lixin DongDr. Senior Research Scientist, Head of NanoRoboticsGroupInstitute of Robotics and Intelligent Systems (IRIS)Swiss Federal Institute of Technology (ETH), ZurichZurich, SwitzerlandAbstract:Progress in robotics over the past years has dramatically extended our ability to explore the world at a variety of scales extending from the edges of the solar system down to individual atoms. At the bottom of this scale, technology has been moving toward greater control of the structure of matter, suggesting the feasibility of achieving thorough control of the molecular structure of matter atom by atom. Nanorobotics represents the next stage in miniaturization for maneuvering nanoscale objects. Nanorobotics is the study of robotics at the nanometer scale, and includes robots that are nanoscale in size and large robots capable of manipulating objects that have dimensions in the nanoscale range with nanometer resolution. Nanorobotic systems emphasize the engineering aspect of nanorobotics and include the manufacturing and application technologies of nanorobotic manipulation systems, nanoelectromechanical systems (NEMS), and nanorobots (nano-sized robots, which have yet to be realized).
The well-defined geometry, exceptional mechanical properties, and extraordinary electrical characteristics of carbon nanotubes (CNTs) qualify them for structuring such systems. Relative displacements between the atomically smooth, nested shells in multiwalled carbon nanotubes (MWNTs) can be used as robust nanoscale motion enabling mechanisms for applications such as bearings, oscillators, shuttles, switches, memories, syringes, and actuators. The hollow structures of CNTs can serve as containers, conduits, pipettes, and coaxial cables for storing mass and charge, or for transport. On the other hand, novel helical nanostructures are created through a top-down fabrication process in which a strained nanometer thick heteroepitaxial bilayer such as SiGe/Si and InGaAs/GaAs curls up to form 3D structures with nanoscale features such as tubes, coils, rings, and spirals. Because of their interesting morphology, mechanical, electrical, and electromagnetic properties, potential applications of these nanostructures include springs, electromechanical sensors, magnetic field detectors, chemical or biological sensors, and inductors.
Shrinking device size to nanometer scales presents many fascinating opportunities such as manipulating nanoobjects with nanotools, measuring mass in zeptogram ranges, sensing forces at piconewton scales, and inducing gigahertz motion, among other new possibilities waiting to be discovered. Nanorobotic manipulation is a promising technology for structuring, characterizing and assembling nano building blocks into NEMS. Combined with recently developed nanofabrication processes, the technological progress on building nanorobotic systems from shell engineered CNTs and rolled up SiGe/Si and InGaAs/GaAs helical nanostructures is presented focusing on nanotube linear servo motors, nanorobotic spot welders using copper-filled nanotubes, and helical nanobelt motion converters.Lixin Dong is Senior Research Scientist at Swiss Federal Institute of Technology (ETH, Zurich), where he leads the NanoRobotics Group in the Institute of Robotics and Intelligent Systems (IRIS). He received the B.S. and M.S. degrees in Mechanical Engineering from Xi'an University of Technology (XUT) in 1989 and 1992, respectively. He became Research Associate in 1992, Lecturer in 1995, and Associate Professor in 1998 at XUT. He has served as the head of the Department of Mechatronics Engineering at XUT from 1997 to 1999. He received his Ph.D. degree in Micro Systems Engineering from Nagoya University in 2003, and became Assistant Professor at Nagoya University in 2003. In 2004 he joined ETH Zurich as a Research Scientist. His main research interests include nanorobotics, mechatronics, nanoelectromechnical systems (NEMS), mechnochemistry, and biomedical devices. He received the IEEE T-ASE Googol Best New Application Paper Award in 2007, Best Conference Paper Award at the Int. Conf. on Control Sci. and Engr. (ICCSE2003), and Finalist in the Best Paper Competition at IEEE-ICRA2007, IROS2005, and ICRA2001. He has been awarded the Science and Technology Advancement Prize by the Ministry of Education of China in 1999, by Shaanxi Province Government in 1999 and 1995, by Xi'an City Government in 1999, and by the Ministry of Machine-Building Industry of China in 1998 and 1992. He serves on the editorial board of the IEEE Trans. on Nanotechnology and the IEEE Trans. on Automation Science and Engineering.Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Novel Nanoscale Materials for the National Ignition Facility
Wed, Apr 16, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Juergen Biener Nanoscale Synthesis and Characterization LaboratoryLawrence Livermore National LaboratoryLivermore, California 94550 Current designs of targets for the National Ignition Facility (NIF) require the development of novel nanoscale materials such as ultra-low density nanoporous metal foams, nanocrystalline metal and diamond films. This talk will provide an overview of the challenges and opportunities associated with the synthesis of these nanoscale materials, and discuss applications beyond NIF targets.
Prepared by LLNL under Contract DE-AC52-07NA27344
Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Long Actuator Delays - Extending the Smith Predictor to Nonlinear
Wed, Apr 23, 2008 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Miroslav KrsticHarold W. Sorenson Professor of Control SystemsDept. of Mechanical & Aerospace EngineeringUniversity of California at San DiegoAbstract: One would be hard pressed to find "long actuator delays" and "nonlinear control" co-existing in the same sentence in the existing control literature, which is due to the infinite dimensionality and the potential for finite escape time instability in the underlying problems. On the 50th anniversary of Otto Smith's invention of the "predictor" feedback for compensating long actuator delays for linear systems, a method that has since become one of the favorite tools in chemical process control and many other applications, I am pleased to present an approach for synthesizing a predictor feedback to go along with any stabilizing nominal nonlinear controller, with actuator delay of any length. Interestingly, Smith's idea was actually an elementary version of "infinite dimensional backstepping," which I have been developing over the last few years for PDE problems such as Navier-Stokes, MHD, Euler and Timoshenko beams, and other systems in mechanics. By employing the backstepping point of view to construct Lyapunov-Krasovskii functionals, it becomes possible to prove several forms of robustness of predictor feedbacks, including robustness to both underestimating and overestimating the length of the actuator delay. The latter is a particularly subtle result because it involves a non-standard dynamic perturbation - the controller (inadvertently) inserts an additional infinite-dimensional state to an already infinite-dimensional feedback loop.
Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Towards Dislocation Dynamics in Carbon Nanotubes and Graphene
Wed, Apr 30, 2008 @ 03:30 PM - 04:30 AM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
This seminar, the last in the Spring AME Seminar Series, will be presented by Elif Ertekin from UC Berkeley.For more information including an abstract, go to http://ame-www.usc.edu/seminars/4-30-08-ertekin.shtml
Location: Seaver Science Library, Room 150 (SSL 150)
Audiences: Everyone Is Invited
Contact: Dennis Plocher