Conferences, Lectures, & Seminars
Events for October
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Mechanics of Stretchable Electronics
Wed, Oct 04, 2006 @ 01:00 PM - 03:00 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
JOINT SEMINAR with AME and CEEYoung HuangShao Lee Soo ProfessorDepartment of Mechanical and Industrial EngineeringUniversity of Illinois at Urbana-ChampaignAbstractStretchable electronics is important in the development of next-generation electronics since it has many applications such as portable electronics, flexible display, small optical sensor and compact digital camera, sensors and drive electronics for artificial muscles, structural monitors wrapped around aircraft wings, and surgeon's gloves studded with stretchable sensors that can monitor a patient's vital signs. However, silicon is an intrinsically brittle material and is not stretchable. We have produced a stretchable form of silicon that consists of sub-micrometer single crystal elements structured into shapes with microscale periodic, wave-like geometries (Science, v 311, pp 208-212, 2006). When supported by an elastomeric substrate, this wavy silicon can be reversibly stretched and compressed to large strains without damaging the silicon. The amplitudes and periods of the waves change to accommodate these deformations, thereby avoiding significant strains in the silicon itself. Dielectrics, patterns of dopants, electrodes and other elements directly integrated with the silicon yield fully formed, high performance wavy metal oxide semiconductor field effect transistors, pn diodes and other devices for electronic circuits that can be stretched or compressed to similarly large levels of strain. There are many mechanics problems in stretchable electronics, and I will discuss a few in this talk.
Location: Hedco Pertroleum and Chemical Engineering Building (HED) - co Neurosciences Bldg. (HNB Auditorium)
Audiences: Everyone Is Invited
Contact: April Mundy
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Scaling Effects on High Strength, High Porosity Nanoporous Metal Foams
Wed, Oct 11, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
JOINT SEMINAR withThe Mork Family Department of
Chemical Engineering and Materials ScienceAndrea M. Hodge Materials Scientist Nanoscale Synthesis and Characterization Laboratory Lawrence Livermore National Laboratory Livermore, CA A comprehensive study including nanoindentation, pillar compression tests and MD simulations of nanoporous Au foams will be presented in order to elucidate on the relationship between mechanical properties, relative density and foam ligament size at the nanoscale. Scaling equations for yield strength and Young's Modulus were investigated using 20% to 42% relative density foams with ligament sizes ranging from 10 to 940 nm. Overall, this study demonstrates that, at the nanoscale, the foam strength is no longer governed by the relative density, but rather by the size of the ligaments. Additionally, experimental results show that nanoporous foams present a new type of high strength, low density material.Location: Stauffer Science Lecture Hall (SLH) Rm 100
Audiences: Everyone Is Invited
Contact: April Mundy
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Forming, Counting, and Breaking Individual Biological Bonds: Applications for Drug Delivery and Sing
Wed, Oct 18, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Todd Sulchek Staff Scientist
Biosecurity and Nanosciences Laboratory
Lawrence Livermore National Laboratory Livermore, CA Protein molecules commonly operate in complexes to perform their function. For example, cell surface receptors often cluster at the site of complementary ligands so as to efficiently transduce binding. A special case of improved functionality through complexed protein binding is demonstrated in a new class of therapeutics in which monovalent antibody binding elements are combined to form multivalent complexes that dramatically increase drug specificity and residency time. However, traditional methods of analysis cannot directly measure the bond lifetime of drug molecules that can bind with a distribution of valencies. Therefore, a single molecule binding assay is illuminating.
We have developed a method using single molecule dynamic force spectroscopy to determine the binding strength of antibody-protein complexes as a function of binding valency in a direct and simple measurement. We used the atomic force microscope (AFM) to measure the force required to rupture a single complex formed by the MUC1 protein, a cancer indicator, and therapeutic antibodies that target MUC1.
We show for the first time that the valency of stochastic, multivalent bond formation can be distinguished with a "molecular counter" in the form of a soft polymer linker. As a result, we independently measure both the valency and the composite bond strength for the interaction. The effective bond lifetime rises dramatically with the number of molecular bonds, from several minutes for a single antibody-antigen bond to many days for three antibody-antigen bonds. Moreover, our results support the theoretical prediction for unbinding dynamics of multiple parallel bonds. We furthermore describe current experiments in which we study cell signal transduction using controlled delivery of protein stimuli.
Location: Stauffer Science Lecture Hall (SLH) Rm 100
Audiences: Everyone Is Invited
Contact: April Mundy
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Social Biological Organisms: Aggregation Patterns and Dynamics
Wed, Oct 25, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Chad Topaz Assistant Professor
and
Assistant Director of Center of Excellence in Teaching
Center of Excellence in Teaching
Rossier School of Education
USC Biological aggregations such as insect swarms, bird flocks, and fish schools are arguably some of the most common and least understood patterns in nature. These groups are thought to arise chiefly from "social forces" acting on individual organisms, including attraction (for protection and mate choice) and dispersion (for collision avoidance). In this talk, I will discuss recent work on continuum (fluid-like) and agent-based models for aggregations. The models describe phenomena such as vortex swarming, population clumping, and group migration. The goal is to determine the relationship between individuals' microscopic rules for movement and the macroscopic properties of the group (such as size, density, and velocity).Location: Stauffer Science Lecture Hall, Room 100 (SLH 100)
Audiences: Everyone Is Invited
Contact: April Mundy
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Investigation of Transport Phenomena in Micro/Nano/Subnano-Scale Channels Applied in Knudsen Compres
Tue, Oct 31, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Y.-L. HanDepartment of Aerospace and Mechanical Engineering
University of Southern CaliforniaInvestigation of transport phenomena is one of the major research topics in micro/nano/subnano-scale (M/N/SN-scale) technologies. Practical applications include concentration, separation, mixing, delivering, pumping, etc. Two specific devices, Knudsen Compressors and Continuous Trace Gas Preconcentrators, have been selected to illustrate the utilization of transport phenomena in micro/nano-scale flows.
Knudsen Compressors are solid-state, micro/meso-scale gas pumps or compressors with no moving parts. Based on the rarefied flow phenomenon of thermal creep, Knudsen Compressors operate by imposing a temperature gradient across a high porosity, low thermal conductivity transpiration membrane. Knudsen Compressors with an aerogel membrane (mean channel size > 20 nm) operated by the radiant heating technique have been studied over a pressure range from about atmospheric pressure down to 10-5 atm. At low pressures, mechanically machined aerogel membranes with circular or rectangular channels have been found to be attractive candidates as Knudsen Compressor membranes. The performance of these membranes has also been found limited by rarefaction effects in the connector section such as "reverse" thermal creep flow and by membrane exit vortices. The Direct Simulation Monte Carlo (DSMC) technique was employed for further investigations of these effects in connector sections of Knudsen Compressors at low pressures. A two-dimensional simulated domain was adopted to mimic a simplified, rectangular channel, single stage Knudsen Compressor. The effects of the "reverse" thermal creep flows and membrane exit vortices have been visualized in the simulations.
The Continuous Trace Gas Preconcentrator is an innovative nano-channel flow application. The operating theory and the preliminary design of the preconcentrator are based on three separation mechanisms: mass separation, quantum separation, and size separation. The separation membranes are an array of aligned channels with nanometer to sub-nanometer size and relatively short lengths. As a consequence of mass separation, size, or quantum separation, the membranes inhibit target molecules from passing through the capillaries while allowing the carrier gas to pass more freely. With a suitable membrane, such as single-walled or multi-walled carbon nanotube membranes, the continuous trace gas preconcentrator is expected to have an excellent performance with a factor of 100 to 1000 times or more increase in the target molecule concentration. The ability to align multi-walled carbon nanotubes has been successfully demonstrated with the construction of a 1cm x 1cm multi-walled array of carbon nanotube towers, and the process of fabricating multi-walled carbon nanotube membranes is ongoing. Fabrication and characterization of a proof-of-concept continuous micro/meso-scale preconcentrator is under way.
It is expected that further research on Knudsen Compressors and Continuous Trace Gas Preconcentrators will yield significant advances in the basic understanding of M/N/SN-scale channel flows as well as efficient micro devices.Location: Laufer Library, RRB 208
Audiences: Everyone Is Invited
Contact: April Mundy