MEAM Seminar Series Fall 2010
Seminars are held on Thursdays at 2:00 p.m. in 337 Towne Building (220 South 33rd Street), unless otherwise noted. Click the date of each seminar to find out additional information about the speaker and topic.
Ju Li, Associate Professor, Department of Materials Science and Engineering, University of Pennsylvania
"Plumber’s Wonderland Found on Graphene"
Katherine Kuchenbecker, Skirkanich Assistant Professor of Innovation, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
"Creating Realistic Virtual Textures from Contact Acceleration Data"
Modern haptic rendering systems excel at conveying the large-scale properties of virtual objects such as shape and stiffness. In contrast, they struggle to provide realistic feedback for surface texture, an important object property that many would like to replicate in the virtual domain. Direct texture rendering challenges the state of the art in haptics because it requires a model of the microscopic surface properties (such as three-dimensional shape, friction, and deformation under load), real-time dynamic simulation of multiple complex tool-surface interactions, and high-bandwidth haptic output to enable the user to feel the resulting contacts. While many alternative texture rendering approaches have previously been proposed, none have succeeded at capturing the rich variations one can experience during tool-mediated contacts with real objects.
Building on our approach of haptography (haptic photography), this talk presents a new, fully-realized solution for capturing and rendering realistic textures within a haptic virtual environment. Like photography for visual stimuli, our system employs a sensorized handheld tool to capture the feel of a given texture, recording three-dimensional tool acceleration, tool position, and contact force over time. We reduce the 3D acceleration signals to a perceptually equivalent one-dimensional signal, and then we use linear predictive coding to distill this raw haptic information into a database of frequency-domain texture models. Finally, we render these texture models in real time with a customized Wacom tablet that includes small voice coil actuators on the stylus. The resulting virtual textures provide a compelling simulation of contact with the real surfaces, earning average realism ratings of five out of seven from human subjects doing direct real-virtual comparisons.
Katherine J. Kuchenbecker is the Skirkanich Assistant Professor of Innovation in Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. Her research centers on the design and control of haptic interfaces for applications such as robot-assisted surgery, medical simulation, and stroke rehabilitation. She directs the Penn Haptics Group, which is part of the General Robotics, Automation, Sensing, and Perception (GRASP) Laboratory at Penn. She has won several awards for her research, including an NSF CAREER Award in 2009, Best Hands-On Demonstration at the 2009 IEEE World Haptics Conference, and Best Haptic Technology Paper at the 2007 IEEE World Haptics Conference. Dr. Kuchenbecker serves on the program committee for the IEEE Haptics Symposium, and she was Co-Chair of Posters, Demos, and Exhibits for this conference in 2010. Prior to becoming a professor, she completed a postdoctoral fellowship at the Johns Hopkins University, and she earned her Ph.D. in Mechanical Engineering at Stanford University in 2006.
Victor Steinberg, Professor of Physics, Weizmann Institute of Science, Rehovot, Israel
"Single vesicle dynamics in various flows: Experiment versus theory"
PhD Thesis Defense
Tuesday, October 5, 2-3 pm, Towne 337
Mian Qin, PhD Candidate
Advisor: Professor Haim Bau
"Microfluidic pumping with surface tension force and magnetohydrodynamic drive"
microfluidic devices, surface tension force is more important than in the larger scales. We designed, fabricated and tested a microfluidic chip with non-uniform conduit cross-sections to induce surface tension imbalance and thus liquid motion. Second, since the samples are usually weakly conducting electrolytes, under imposed electric and magnetic fields, Lorentz body force is generated and could propel the liquid. The magneto-hydrodynamic (MHD) pumping requires only externally applied electric and magnetic fields without a need for moving elements. We studied the electro-kinetics, flow characteristics, electric current
injection and Taylor-Aris dispersion associated with MHD flow in a uniform conduit and around pillar arrays. We also studied MHD flow of a binary electrolyte in an annular conduit and the flow instability triggered by conduit curvature and magnified by electrochemical mass transfer. This work will guide the design of MHD driven, cyclic chromatographic devices, and the design of operating conditions which introduce or eliminate transverse fluid motion depending on the nature of the application.
T. Sundararajan, Professor, Thermodynamics Combustion Engineering Lab and Department of Mechanical Engineering, IIT Madras
"Micro- and nano- scale phenomena in heat transfer and fluid flow"
Miniaturization has become the by-word in electro-mechanical and bio-MEMS systems. The heat transfer and fluid flow processes taking place at such minute scales differ considerably from their macro-scale counter parts. In this lecture, our work on three related (and yet distinct) classes of small scale heat transfer and flow problems is described.
The first problem deals with hyperbolic heat conduction through thin metallic layers at very small times. Due to the sudden imposition of large heat flux at the metal surface, the electron and phonon temperatures are different- at very small times, heat waves propagate in a hyperbolic conduction process due to electrons; subsequently, smooth Fourier- type heat conduction occurs which is dominated by the energy transfer of phonons. The problem of laser pulse- heating has been studied as an application problem in this context.
The second problem deals with the enhancement of effective conductivity of heat transfer fluids by the suspension of nano-sized metallic and oxide particles. Experimental data on effective conductivity have been gathered using the transient hot-wire technique. Theoretical models have also been developed which explain the dependence of effective conductivity on particle size, particle concentration and solvent temperature. It is shown that the lower resistance path for heat transfer provided by the nano- particles is responsible for the increase in conductivity. Since the level of enhancement depends on the increase in surface area (per unit volume) for heat transfer as well as the average particle migration velocity, strong dependence is observed on particle size and solvent temperature. With the addition of carbon nano-tubes, the enhancement in conductivity is very high because of the formation of connected paths (networks) for good heat transfer.
The third problem considers the anomalous variation of pressure drop with flow rate in micro-channels. Experimental and theoretical work has been carried out, which illustrates that compressibility effects are important in micro-channel gas flows due to the variation of density with pressure across the channel. For flow of water, dissolved gases affect the pressure drop characteristics. These phenomena explain some of the anomalies reported with regard to micro-channel flows. It is also shown that continuum models are adequate to explain flow phenomena in channels with hydraulic diameters ranging between 50-100 microns, and there is no need to consider any slip-flow models. In multiple micro-channels, local flow separation gives rise to mal-distribution of flow between channels. The dependence of flow mal-distribution on flow rate, geometric parameters and fluid viscosity is discussed in detail.
Curriculam Vitae of T.Sundararajan
Dr. T. Sundararajan is a Professor in the Department of Mechanical Engineering at Indian Institute of Technology (IIT) Madras. He completed his Bachelor’s degree in Mechanical Engineering from IIT Madras in 1978, MS and PhD in the years 1980 and 1983 from the University of Pennsylvania at Philadelphia. After a brief stint as post-doctoral fellow at UPenn for about 18 months, he took up academic career as an Assistant Professor at IIT Kanpur in India. Later he shifted to IIT Madras and became a full Professor in 1995.
Prof. Sundararajan has published about 130 journal papers in archival journals and presented more than 100 papers in conferences. He is a co-editor and author of a book on Computational Fluid Flow and Heat Transfer. His research covers areas such as Computational modeling of heat transfer & fluid flow, Spray combustion, Multi-phase flow modeling, Jet flows, Nuclear thermal hydraulics and High speed flows. He has guided 26 PhD and 32 MS students in their thesis work. He has also carried out several sponsored projects for agencies such as the Indian Space Research Organization (ISRO), Indira Gandhi Centre for Atomic Research (IGCAR), Aeronautical Research & Development Board (AR&DB), Department of Science and Technology (DST) and the Defence Research & Development Laboratories (DRDL).
Prof. Sundararajan is an elected Fellow of the Indian National Academy of Engineering.
Wednesday, October 13, 2-3 pm, Towne 337
G. Paul Neitzel, Professor of Fluid Mechanics and Associate Chair for Graduate Studies, George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology
"Permanent Noncoalescence and Nonwetting:Science and Applications"
Under the proper conditions it is possible to press together two drops of the same liquid without experiencing coalescence or to press a liquid droplet against a surface normally wetted by the liquid without wetting occurring. By permanent noncoalescence and nonwetting we distinguish cases in which the phenomena may be observed for unlimited time from transient examples such as two drops of liquid bouncing off one another or a liquid droplet bouncing off a solid wall. To achieve permanent noncoalescence or nonwetting, a mechanism is needed for establishing a lubricating film of surrounding fluid (usually air) and sustaining this film as the liquid/liquid or solid/liquid surfaces are moved toward each other.
This talk will address means for the establishment of such lubricating films and discuss measurements and theory conducted to understand the behavior of such systems. Finally, possible applications of permanent noncoalescence and nonwetting will be described, including a demonstration of droplet levitation above a solid surface using non-contact, optical methods.
G. Paul Neitzel has been a Professor in The George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology since 1990; he presently also serves as Associate Chair for Graduate Studies. Prior to arriving at Georgia Tech, he served for eleven years on the faculty of the Department of Mechanical and Aerospace Engineering at Arizona State University and worked ten years at the U.S. Army Ballistic Research Laboratory, during which time he received his Ph.D. in fluid mechanics from The Johns Hopkins University. He has conducted research on the hydrodynamic stability of unsteady swirling flows and flows associated with materials processing, vortex breakdown, suppression of coalescence/wetting and bioreactor fluid dynamics. He is a Fellow of the American Physical Society and the American Society of Mechanical Engineers, an Associate Fellow of the American Institute of Aeronautics and Astronautics and the recipient of a National Science Foundation Presidential Young Investigator Award and an Alexander von Humboldt Fellowship. He has served as a visiting professor at the Universität Karlsruhe (Germany), Imperial College of Science and Technology (London) and the Université d’Aix-Marseille II and a visiting scientist at Forschungszentrum Karlsruhe (Germany).
William Klug, Associate Professor, Mechanical and Aerospace Engineering, University of California at Los Angeles
"The Solid Mechanics of Fluid Shells: Understanding Structure and Organization in Cell Membranes"
Cellular membranes are heterogeneous 2-dimensional fluids of lipids, proteins and other small molecules. The use of cryo-electron tomography and confocal microscopy is producing an ever growing database of detailed 3-dimensional membrane conformations capturing the structure and molecular organization of biomembranes in cellular processes ranging from viral budding and organelle maintenance to signaling and trafficking. This wealth of experimental data demands generic, quantitative methods for interpretation of the physical mechanisms that produce and maintain the structure and order in cellular membranes.
In this talk I will present a computational framework for quantitative analysis of the mechanics of biomembranes, built on Lagrangian finite-element discretization of continuum mechanics models based on large deformation shell theory, employing artificial viscosity techniques for r-adaptive remeshing for robust simulation of external loadings and large membrane deformations. I will then focus on two applications of the framework for understanding cellular membrane structure. First, I will discuss a systematic method for using membrane shape (as determined by microscopy or tomography) as a reporter for applied forces. By modeling observed biomembrane shapes as fluid lipid bilayers in mechanical equilibrium, the externally applied forces as well as the pressure, tension, and spontaneous curvature can be computed directly from the shape alone. To illustrate the potential power of this technique, I will present the results of experimental application of an axial force with optical tweezers to vesicles, explicitly demonstrating that the applied force is equal to the force computed from the membrane conformation. Next I will turn attention toward understanding mechanical stability and interactions for phase-separated membrane domains, known as “lipid rafts.” Presenting results of a combination of mechanical modeling and in vitro experiments, I will show how lipid domains can buckle into a dimpled morphology, which facilitates a repulsive interaction that slows coalescence and helps regulate domain size and tends to laterally organize domains in the membrane.
Eric Lauga, Associate Professor, Department of Mechanical and Aerospace Engineering, University of California, San Diego
"Synchrony and optimality in cellular hydrodynamics"
Fluid mechanics plays a crucial role in many cellular processes. One example is the external fluid mechanics of motile cells such as bacteria, spermatozoa, algae, and essentially half of the microorganisms on earth. The most commonly-studied organisms exploit the bending or rotation of a small number of flagella (short whip-like organelles, length scale from a few to tens of microns) to create fluid-based propulsion. As a difference, ciliated microorganisms swim by exploiting the coordinated surface beating of many cilia (which are short flagella) distributed along their surface. In this talk, after a short introduction to the fundamentals of fluid-based locomotion, we consider problems related to synchrony and optimality. First, we address theoretically the observed flagellar synchronization between eukaryotic cells swimming in close proximity. By using a two-dimensional model, we show analytically and computationally that synchronization between co-swimming cells can be driven by hydrodynamic interactions alone if there is a geometrical symmetry-breaking displayed by the their flagellar waveforms. The physical origin of this symmetry-breaking is also discussed. In a second part, we pose the problem of ciliary propulsion as an optimization problem. Specifically, for a spherical body, we compute numerically and theoretically the time-periodic tangential deformations of the body surface which leads to swimming of the body with optimal hydrodynamic efficiency. We show that this calculation leads to symmetry-breaking in the surface actuation, and the emergence of waves, reminiscent of the metachronal waves displayed by real biological cilia. We also address the issue of optimal shapes of swimming organisms, both for eukaryotes and prokaryotes.
Bong Jae Lee, Assistant Professor, Department of Mechanical Engineering and Materials Science, University of Pittsburgh
"Tailoring Radiative Properties using Nanostructures"
Tailoring thermal radiative properties using micro- and nano-structured surfaces has drawn much attention due to potential applications in energy conversion devices, space thermal management, and infrared radiation detection. This presentation describes a theoretical and experimental study about the coherence of thermal emission from a truncated one-dimensional photonic crystal atop a metallic layer. Surface electromagnetic waves can be excited at the edge of photonic crystal, enabling the spectral- (i.e., temporal coherence) and directional-selectivity (i.e., spatial coherence) in the emissivity. The key phenomenon known as surface plasmon or phonon polaritons will be elucidated along with the concept of the photonic bandgap.
Besides photonic crystals, coherent emission characteristics can also be achieved by exciting magnetic polaritons between metallic gratings and an opaque metallic film, separated by a dielectric spacer. The coupling of the metallic strips and the film induces a magnetic response that is characterized by a negative permeability and positive permittivity. On the other hand, the metallic film intrinsically exhibits a negative permittivity and positive permeability in the near infrared. Therefore, this artificial structure is equivalent to a pair of single-negative materials, resulting in large emissivity peaks that are almost independent of the emission angle at resonance frequencies.
Finally, this presentation will outline the current and future research activities in modeling the radiative properties of multidimensional nanostructures, including two-dimensional, dielectric-layered metallic structures on top of which square cross-sectional nanowires are vertically aligned as well as core-shell nanowire structures.
Biography: Dr. Bong Jae Lee is an Assistant Professor in the Department of Mechanical Engineering and Materials Science at the University of Pittsburgh. He received his B.S. degree in Mechanical Engineering from Seoul National University in 2001 and his M.S. and Ph.D. degrees from the Georgia Institute of Technology in 2005 and 2007, respectively. Dr. Lee was the winner of the Georgia Tech Chapter of Sigma Xi Best Ph.D. Thesis Award in 2008 and was the recipient of the Hewlett Packard Best Paper Award (2nd place) in 2007. His research interests include nanoscale energy transport phenomena, light-matter interaction at the nanoscale, plasmonics, and metamaterials. In particular, he is interested in investigating fundamental physics of near-field thermal radiation, tailoring radiative properties of nanostructures, and employing engineered nanostructures to novel energy conversion and biosensing devices.
Wednesday, November 17, 2-3 pm, Berger Auditorium, Skirkanich Hall
Alexander Morozov, EPSRC CAF Research Fellow, School of Physics & Astronomy, University of Edinburgh
"Instabilities in viscoelastic shear layers and their relation to elastic turbulence"
Newtonian fluids are known to exhibit hydrodynamic instabilities and/or transition to turbulence at large enough Reynolds numbers. Recently, it has been discovered that flows of dilute polymers in simple geometries can also become unstable at very low Reynolds numbers. These purely elastic instabilities are not caused by inertia but instead are driven by anisotropic elastic stresses. Further increase of the flow rate results in a truly chaotic flow -- purely elastic turbulence.
In this talk I will discuss an attempt of modelling purely elastic turbulence. Recently, our understanding of the transition to Newtonian turbulence has significantly changed due to the discovery of the exact solutions of the Navier-Stokes equations. I will review the modern developments in Newtonian turbulence and attempt to construct a generalisation of this theory to viscoelastic flows. I will discuss how various parts of the self-sustaining process are affected by the presence of polymers and its relevance to drag reduction and purely elastic turbulence.
James Feng, Professor and Canada Research Chair, Departments of Chemical and Biological Engineering and Mathematics, University of British Columbia, Vancouver, Canada
"Interfacial Dynamics in Complex Fluids"
PhD Thesis Defense
Friday, November 19, 3 pm, Towne 337
Jack Franklin, PhD Candidate
Advisor: Jennifer Lukes
"Patterning of Alloy Precipitation Through External Pressure"
Lev Truskinovsky, Laboratoire de Mécanique des Solides, Ecole Polytechnique, France; William and Flora Hewlett Foundation Fellow and Wyss Visiting Fellow, Dept. of Mechanical Engineering, Harvard University
"Criticality in plasticity"
Hao Lin, Assistant Professor, Mechanical and Aerospace Engineering, Rutgers University
"Electric Field Mediated Transport in Lab-on-a-chip and Biological Systems"
During the past decade, electric-field-mediated transport has been widely leveraged in fluidic and biological systems to enable novel functionalities and spawn technological innovations. The strong electromechanical coupling of the electric field and electrolyte solution in these applications often leads to new and complex flow behavior which challenges fundamental understanding and prediction capability. In this work I will explore such phenomena in both lab-on-a-chip and biological systems. In the first, I will demonstrate the basics of electrokinetic (EK) and electrohydrodynamic (EHD) flows, and that we can accurately predict these phenomena with an appropriate framework. In the second, such model is extended to study electroporation-mediated molecular delivery. In this latter technology, the electric field is used to transiently permeabilize the cell membrane, such as to deliver active molecules into the intracellular compartment. The objective of this study is to identify the mechanisms involved in molecular delivery, and to use fundamental understanding and prediction capability to improve this promising technology.
Dr. Hao Lin received his BS degree in Mechanics from Peking University in 1996, and PhD in Mechanical Engineering from University of California, Berkeley in 2001. He was a postdoctoral fellow in the Center for Turbulence Research at Stanford University from 2001 to 2003, and a postdoctoral researcher in the Mechanical Engineering department from 2003 to 2005. He joined the faculty of Mechanical and Aerospace Engineering at Rutgers University in July, 2005. He has worked on various research areas including cavitation and sonoluminescence, and large scale fluid flow in astrophysical systems. His present interests are in the transport and fluid flow on the micro- and nano-scales. In particular, he has expertise in modeling and experimental investigation of electric-field-mediated transport in both lab-on-a-chip and biophysical/biomedical systems. He is a recipient of the NSF CAREER Award in 2008, and the Presidential Early Career Award for Scientists and Engineers (PECASE) in 2010.
Jimmy Sastra, PhD Candidate
Advisor: Mark Yim
"Using Modular Reconfigurable Robots as a Platform for Dynamic Locomotion Experiments"
The idea behind Modular Reconfigurable Robotics is to design a module and build many copies of it. The result is a system you can put together in different ways with different morphologies. While this field is already well established, most efforts have been focused on topics such as reconfiguration and distributed algorithms. Because of this most Modular Robots are heavily geared down and slow resulting in locomotion gaits that that are slow and statically stable. They do not take advantage of the exchange in energies or momentum like in dynamic locomotion.
In this work we propose that Modular Robots can do dynamic locomotion, previously never been shown, by creating modules that are fast. We have implemented many dynamic gaits and we will highlight two of these. One is a wheel like motion, which turned out to be the fastest gait in the community at 1.4m/s and the other is a underactuated legged type of motion with compliant appendages like a centipede. We present our analysis and experimental sensing setup for these gaits and we show that Modular Robots can in fact perform dynamic locomotion and contribute to the field of dynamic robot locomotion.