MEAM Seminar Series Fall 2018

For Summer 2018 Seminars, click here.

Seminars are held on Tuesday mornings beginning at 10:45 am in Wu and Chen Auditorium, in the Levine Building (unless otherwise noted).

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September 4


September 11

Tamer Zaki, Associate Professor, Department of Mechanical Engineering, Johns Hopkins University

"Harbingers of Turbulence in Boundary Layers"


The manner in which infinitesimal disturbances can cause organized fluid motion to become chaotic is an intriguing phenomenon. In addition to being of great theoretical interest, laminar-to-turbulence transition is of significant engineering importance due to its role in heat transfer, its influence on momentum mixing, and its effect on drag. In this work, we present complementary theoretical analyses, high-fidelity direct numerical simulations and data-enabled predictions of transition to turbulence in boundary layers.

The proceedings of transition are not unique, and various pathways can ultimately lead to boundary-layer turbulence. These pathways have traditionally been grouped in two classes: the orderly and the bypass routes. Orderly transition has its origin in classical linear stability theory, which predicts a slow transition process starting from weak Tollmien-Schlichting instability waves. In engineering applications, the presence of free-stream disturbances promotes early breakdown to turbulence, and transition is said to “bypass” the classical Tollmien-Schlichting route.

Numerical simulations of bypass transition reveal that high-frequency disturbances from the free stream are expelled by the boundary-layer shear – a phenomenon known as shear sheltering. Using asymptotic analysis, we develop a physical understanding of the mechanics of shear sheltering, and explain how low-frequency free-stream perturbations can permeate the mean shear. These elongated disturbances force the boundary layer resonantly and lead to the amplification of streaks.

While the majority of the laminar streaks are innocuous, a small proportion undergoes a localized instability and breaks down to turbulence. Reports in the literature present conflicting views on the origin of streak breakdown – a matter that we address by performing secondary instability analyses of realistic streaks as well as using artificial neural networks. The predicted streak instabilities are shown to cause breakdown to turbulence in complementary direct numerical simulations.


Tamer Zaki is an associate professor in the Department of Mechanical Engineering at Johns Hopkins University. His current research activity spans transitional and turbulent shear flows, interfacial flows and complex fluids. Dr. Zaki received his PhD in 2005 from Stanford University where he was a member of the Flow Physics and Computational Engineering group. He participated in the Department of Energy Advanced Simulation and Computing (DoE-ASC) program both at Stanford and at Los Alamos National Lab where he was awarded the “Directors Fellowship”. He joined the faculty in the Department of Mechanical Engineering at Imperial College London (2006–2012) where he established the Flow Science and Engineering group, followed by his current appointment at Johns Hopkins. He is a member of the Johns Hopkins Institute of Data Intensive Engineering and Science (IDIES), the Center for Applied and Environmental Fluid Mechanics (CEAFM), the American Physical Society and the Editorial Advisory Board of Flow, Turbulence and Combustion.


September 13 (Thursday): MEAM Ph.D. Thesis Defense

Tarik Tosun, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Mark Yim

"Reconfigurable Robots: Systems that Transform Themselves and Their Environments"

2:30 p.m., Room 337, Towne Building


Developing flexible, broadly capable systems is essential for robots to move out of factories and into our daily lives. In this talk, I will present robots that adapt to new tasks by reshaping themselves and their environments.

SMORES-EP is a modular self-reconfigurable robot, composed of repeated robot elements (called modules) that connect together to form larger structures. By rearranging its modules, SMORES-EP can assume morphologies suitable to a wide range of tasks (e.g. a car to maneuver on flat ground, a snake to climb stairs, or an arm to pick and place objects). Reconfigurability introduces complexity: addressing a task requires first selecting an appropriate morphology for the robot, which has implications for sensing, planning, and control. I will present work in hardware design, algorithms, and task planning frameworks that has culminated in an integrated system allowing modular robots to complete tasks autonomously. Users specify tasks in terms of constraints and desired outcomes, and appropriate behaviors are automatically selected to meet task requirements. Whenever the task or sensed environment requires a particular capability, the robot autonomously self-reconfigures to a morphology that has that capability.

Beyond self-reconfiguration, my research also explores a strategy called environment augmentation, in which robots alter their environments by building structures to make a task easier. In the final portion of my talk, I will demonstrate how SMORES-EP can autonomously build structures to surmount large obstacles, and present a algorithm to synthesize a min-cost set of structures a robot could build to make its entire environment traversable.

September 18

Nanshu Lu, Associate Professor, Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin

“Mechanics, Manufacture, and Validation of Soft Bioelectronics”


Bio-tissues are soft, curvilinear and dynamic whereas wafer-based electronics are hard, planar, and rigid. Over the past decade, stretchable high-performance inorganic electronics have emerged as a result of new structural designs and unique materials processes. Electronic tattoos (e-tattoos) represent a class of stretchable circuits, sensors, and stimulators that are ultrathin, ultrasoft and skin-conformable. This talk will first introduce stretchable serpentine structures followed by a dry and freeform “cut-and-paste” method to fabricate e-tattoos within minutes. This method has been proved to work for thin film metals, polymers, ceramics, as well as 2D materials such as graphene. I will demonstrate the unique advantages of such disposable e-tattoos as a mobile and disposable platform for continuous vital sign monitoring, human-robot interface, as well as personalized therapeutics. Examples include sensors for electroencephalogram (EEG), electrocardiogram (ECG), electromyogram (EMG), electrooculogram (EOG), skin temperature, skin hydration, respiratory rate, blood pressure, oxygen saturation, as well as chemical biomarkers in sweat (e.g. glucose and lactate). For wireless power and data transmission, NFC-enabled e-tattoos based on stretchable antenna and Bluetooth-enabled e-tattoos will be demonstrated. Bio-electronics interface conformability, blistering, and reversible adhesion will also be discussed.


Nanshu received her Ph.D. from Harvard University in 2009 and spent two years as a Beckman Postdoctoral Fellow at UIUC. She joined the University of Texas at Austin in 2011 and became tenured Associate Professor in 2017. She has published more than 70 journal articles with more than 8000 citations in the field of soft bioelectronics. She has been named 35 innovators under 35 by MIT Technology Review and has received NSF CAREER Award, multiple DOD Young Investigator Awards and 3M Non-Tenured Faculty Award.

September 25

Lian-Ping Wang, Professor, Department of Mechanical Engineering, University of Delaware

"Boltzmann Equation-based Computational Fluid Dynamics"


Since the 1980s, direct numerical simulations have served as a vital research tool to probe flow structures and nonlinear dynamics in complex flows such as multiphase flows and turbulent flows. Most of these simulations were performed based on the continuum (conventional or macroscopic) Navier-Stokes equation. In recent years, mesoscopic methods based on the Boltzmann equation, such as the lattice Boltzmann method and gas kinetic schemes, have been developed and applied to these complex flows. In this talk, I will discuss some recent advances in applying mesoscopic methods for rigorous simulations of such complex flows. Three specific examples will be considered: (a) turbulent channel flow laden with finite-size moving particles, (b) hydrodynamic interactions of cloud droplets, and (c) compressible turbulent flow. A few implementation issues in these simulations will be discussed. The purpose is to expose the capabilities of these mesoscopic methods, open research issues, and their potentials for various complex flow problems.


Dr. Lian-Ping Wang received a Bachelor’s degree in Mechanics from Zhejiang University, China; and a PhD in Mechanical Engineering from Washington State University, USA. He worked as a Visiting Research Associate at Brown University and a Research Associate at Pennsylvania State University, before joining the University of Delaware in 1994. He was promoted to Professor of Mechanical Engineering in 2010. In 2017, he was appointed a Chair Professor of Mechanics and Aerospace Engineering at SUSTech (part-time). Dr. Wang uses advanced simulation tools and theoretical methods to study multiphase flows and transport in engineering applications and environmental processes. His research covers direct and large-eddy simulations of turbulence and particle-laden flows, modeling and parameterizations of dispersion and turbulent collision of inertial particles, and simulation of interfacial multiphase flows. He develops and applies Boltzmann-equation based kinetic schemes, pseudo-spectral, and finite-difference / finite-volume methods for a variety of applications, as well as their scalable implementations on parallel computers. Dr. Wang is a Fellow of American Physical Society and a Fellow of American Society of Mechanical Engineers.

October 2


October 5 (Friday): MEAM Ph.D. Thesis Defense

Yuejun Yan, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Noam Lior

"Combustion Irreversibility Analysis and Reduction"

10:30 a.m., Room 309, Towne Building


The massive global use of combustion and the large exergy destruction in fuel combustion which is typically 20% to 30% of the useful energy highlight the importance of seeking for more exergy-efficient combustion. This dissertation pursued quantitative understanding of the reasons for the irreversibilities, i.e., their cause, location and magnitude, and recommended approaches for reducing them. This was studied by two different approaches: 1) the conventional and most frequently numerical way, the intrinsic analytical method (IAM) based on the solution of the system differential equations, which requires complex computation, and 2) the novel heuristic finite increment method (HFIM) that solves a system of algebraic equations, which is an orders-of-magnitude computationally easier approximation.

The results demonstrated that the overall exergy destruction ratio computed by the IAM (22.58%) and the HFIM (19.6% to 22.3% for the 14 paths) agreed well for the studied adiabatic isobaric hydrogen/air combustion. The fractions of the individual contributors (chemical reaction, heat transfer, mass transfer and viscous dissipation) to the overall exergy destruction in the two approaches, however, were quite different. The IAM predicted that the chemical reaction is the dominant contributor (at 80.56%), while the HFIM predicted that the heat transfer is the dominant one (at 47.4 % to 72.1%). The difference was explained, for the first time, and it was because the HFIM assumed the combustion occurring in a prescribed path that made the chemical reaction rate at low temperature higher than reality. This established the connection of the two different approaches.

Ways to reduce irreversibilities, by the sensitivity analysis in the IAM, comprised of reducing the excess air coefficient, increasing the inlet temperature, making the combustor walls as close as possible to adiabatic and optimizing the inlet velocity. Methods to decrease irreversibilities, by analyzing 14 hypothetical paths in the HFIM, were applying stoichiometric oxygen combustion and heat recirculation from high-temperature to low-temperature chambers.

This dissertation also compared the exergy destruction results for similar combustion conditions computed by the HFIM and the IAM for the first time. The comparison enabled the identification of the hypothetical paths in the HFIM which are the closest to reality.


October 8 (Monday): MEAM Ph.D. Thesis Defense

Sikang Liu, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Vijay Kumar

"Motion Planning for Micro Aerial Vehicles"

1:00 p.m., Room 337, Towne Building


The Micro Aerial Vehicle (MAV) is capable of agile motion in 3D making it an idea platform for developments of planning and control algorithms. For fully autonomous MAV systems, plan motions that are both dynamically feasible and collision-free in cluttered environments are essential. Recent work demonstrates precise control of MAVs using time-parameterized trajectories that satisfy feasibility and safety requirements. However, planning such trajectories is non-trivial, especially when considering constraints, such as optimality and completeness. For navigating in unknown environments, the capability for fast re-planning is also critical. Considering all of these requirements, motion planning for MAVs is a challenging problem. In this thesis, we examine trajectory planning algorithms for MAVs and present methodologies that solve a wide range of planning problems. We first introduce path planning and geometric control methods, which produce spatial paths that are inadequate for high speed flight, but can be used to guide trajectory optimization. We then describe optimization-based trajectory planning and demonstrate this method for solving navigation problems in complex 3D environments. When the initial state is non-static, an optimization-based method is prone to generate sub-optimal trajectories. To address this challenge, we propose a search-based approach using motion primitives to plan resolution optimal and complete trajectories. This algorithm can also be used to solve planning problems with constraints such as motion uncertainty, limited field-of-view and moving obstacles. The proposed methods can run in real time and are applicable for real-world autonomous navigation, even with limited on-board computational resources. We conclude by analyzing the strengths and weaknesses of our planning paradigms and demonstrating their performance through simulation and experiments.


October 9: MEAM Ph.D. Thesis Defense

James Hilbert, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Robert Carpick

"Understanding and Improving the Environmental Dependent Tribology and Thermal Stability of Hydrogenated Amorphous Carbon by Using Silicon and Oxygen as Dopants"

8:30 a.m., Towne 337


Hydrogenated amorphous carbon (a-C:H) films are a class of non-crystalline materials composed of hydrogen and carbon bonded in both sp2 and sp3 configurations. These films are notable for their high hardness (10-16 GPa), low roughness, chemical inertness, and good tribological performance (low friction and wear). This combination of favorable properties has led to promising applications in diverse fields, including automotive and aerospace components, biomedical devices, and computer hard drives. However, a-C:H becomes unstable above 150 °C, preventing its use in important technological applications, such as heat assisted magnetic recording (HAMR) disk drives. Also, the low friction and wear is only maintained in dry and vacuum conditions. To understand and address these limitations, the effect of adding silicon and oxygen to a-C:H films is considered, since prior experimental evidence shows that this can significantly increases thermal stability, and help maintain low friction and wear in humid environments. However, the mechanisms and extent of these improvements are unknown. Friction and wear testing were performed on a-C:H doped with Si and O (a-C:H:Si:O) in a range of environments. Friction coefficients varied from approximately 0.05 in dry environments (RH < 5%) to 0.15 in humid air, better than prior observations for undoped a-C:H films. The friction and wear behavior is controlled by adhesive interactions leading to the development of transfer films on the steel counterface. Possible mechanisms underlying this behavior are discussed. Annealing experiments showed significant improvements in thermal stability up to 450 °C. In order to understand the atomistic origins of this enhanced thermal stability, reactive molecular dynamics (MD) simulations using the ReaxFF potential were performed. The primary thermal degradation pathway in undoped a-C:H was observed to be the breaking of tensile strained C-C bonds. The presence of Si suppresses this mechanism by decreasing the frequency of highly strained C-C bonds in the unannealed structure. This is due to the longer C-Si equilibrium bond length compared to C-C bonds. The activation energy for rehybridization could be modeled using the same methods as in prior experiments and produced good agreement between the experimental and simulation results.

October 9: Technology, Business and Government Lecture

Ralph Izzo, Chairman of the Board, President, and Chief Executive Officer, Public Service Enterprise Group, Inc.

"The Future of Energy"


For most of the last century, American utilities were on a mission to spread the availability of electricity and natural gas as far and as wide as possible. But the energy sector is undergoing an evolution in response to changing customer demands - led by our global commitment to tackle the challenges of climate change. PSEG Chairman, President and CEO Ralph Izzo will discuss the state of the energy sector and how the industry and his company must adapt to a changing world.


Ralph Izzo was elected chairman and chief executive officer of Public Service Enterprise Group (PSEG) in April 2007. He was named as the company’s president and chief operating officer and a member of the board of directors of PSEG in October 2006. Previously, Mr. Izzo was president and chief operating officer of Public Service Electric and Gas Company (PSE&G). He joined the company in 1992.

Mr. Izzo is on the board of directors for the New Jersey Chamber of Commerce, the Edison Electric Institute (EEI), the Nuclear Energy Institute (NEI) and the New Jersey Performing Arts Center. He also is on the advisory board for the University of Pennsylvania’s School of Engineering and Applied Sciences Mechanical Engineering and Applied Mechanics Department, a member of the Board of Trustees of the Peddie School and Princeton University’s Andlinger Center for Energy and the Environment Advisory Council, as well as a member of the Visiting Committee for the Department of Nuclear Engineering at Massachusetts Institute of Technology and the CEO Action for Diversity and Inclusion. Mr. Izzo is a former member of the Columbia University School of Engineering Board of Visitors. In addition, he is a former chair of the Rutgers University Board of Governors and the New Jersey Chamber of Commerce.

October 10 (Wednesday): MSE Ph.D. Thesis Defense

J. Brandon McClimon, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Robert Carpick

"Tribological Response of Silicon Oxide-containing Hydrogenated Amorphous Carbon, Probed Across Lengthscales"

11:00 a.m., Room 3W2, David Rittenhouse Laboratory Building


This work examines the structure and properties of silicon-oxide containing hydrogenated amorphous carbon (a-C:H:Si:O) thin films, and how the structure and properties are responsible for the fundamental tribological response of the material. The films are studied through a range of spectroscopic techniques, focused on the surface-sensitive X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopies. The tribological response is studied at several lengthscales: using macroscale ball-on-flat tribometry, at the nanoscale with sharp diamond-like carbon-coated AFM probes, and at the microscale with steel colloids affixed to AFM cantilevers. The spectroscopic study reveals that the films contain a high fraction of SiOx which leads to a structure rich in sp3 carbon-carbon bonding that affords strong protection against oxidative attack at the elevated temperatures in aerobic environments, which is important for demanding applications. At the macroscale, low friction coefficients are achieved upon the formation of an inherently lubricious, soft and polymeric tribofilm whose composition and structure depends heavily on the sliding environment, while the lubriciousness of the resulting tribofilm does not depend on the environment in which it was formed. Nanoscale experiments demonstrate that the shear strength of a sharp, single asperity contact sliding on a-C:H:Si:O is at least an order of magnitude higher than those estimated from macroscale sliding, raising questions about whether the surface passivation theory of DLC lubricity is sufficient to explain macroscale lubricity. Colloidal AFM experiments show, in situ, that low friction is achieved with the growth of the tribofilm via a combination of reduced adhesion and a precipitous drop in the shear strength, which offset a simultaneous increase in the real area of contact. The compilation of results suggest a model of lubrication which relies on both surface passivation of the counterfaces and the soft and viscoelastic properties of the tribofilm, which reduce the effect on friction of nanoasperity pinning.

October 16

Yong Zhu, Professor, Department of Mechanical and Aerospace Engineering, North Carolina State University

"From Single Nanowire to Nanowire Network: Mechanics and Application in Stretchable Electronics"


Nanowires are among the most important building blocks for nanotechnology. A plethora of metallic, semiconducting and ceramic nanowires have been synthesized. Recently stretchable electronics has received much attention due to their promising applications – where electronics undergoes large deformation and/or forms conformal contact with curvilinear surfaces – including wearable sensors, electronic skin, and soft robotics, to name a few. Nanowires have been widely used in stretchable electronics, which brings forth a host of interesting mechanics problems at multiple length scales from single nanowire to nanowire/polymer interface to nanowire network. In this talk, I will discuss two examples highlighting the fundamental and applied aspects of nanowire-enabled stretchable electronics. For the fundamental aspect, I will talk about mechanical behavior of single Si nanowires. We show, using MEMS-based in situ nanomechanical testing in transmission electron microscopy, that Si nanowires under tension are brittle at room temperature, but exhibit pronounced plasticity at elevated temperatures. We discover an unconventional slip system that becomes highly active with increasing temperature, leading to the brittle to ductile transition (BDT) in Si nanowires. For the applied aspect, I will focus on stretchable electronics using metallic nanowires. Percolation networks of metallic nanowires, when integrated with soft matrix, can make high-performance stretchable conductors. Based on this technology, we have developed a range of wearable sensors for health and activity monitoring as well as human-machine interface, flexible bimorph actuators for soft robotics, and wearable antennas for wireless body-area network systems. Scalable manufacturing of nanowire-based stretchable electronics will also be discussed.


Yong Zhu is a Professor in the Department of Mechanical and Aerospace Engineering, with joint appointments in the Departments of Materials Science and Engineering and Biomedical Engineering, at North Carolina State University (NCSU). He received his Ph.D. from Northwestern University and was a postdoctoral fellow at the University of Texas at Austin before joining NCSU in 2007. His group conducts research at the intersection of solid mechanics and micro/nano-technologies, including microelectromechanical systems (MEMS), nanomechanics, and nanomaterial-enabled stretchable electronics. His work has been recognized by a number of awards including Alcoa Foundation Research Achievement Award at NCSU, Society of Experimental Mechanics Young Investigator Lecture Award, ASME Sia Nemat-Nasser Early Career Award, Eshelby Mechanics Award, and the Best Wearable Material/Component Development Award at IDTechEx Wearable USA. Zhu serves in the executive committee of the ASME Materials Division (Chair 2019-2020). He is an Associate Editor for Journal of Applied Mechanics and Journal of Experimental Mechanics while on the editorial boards of several journals.


Richard D. James, Distinguished McKnight University Professor, Department of Aerospace Engineering and Mechanics, University of Minnesota

"Atomistically Inspired Origami”


World population is growing approximately linearly at about 80 million per year. As time goes by, there is
necessarily less space per person. Perhaps this is why the scientific community seems to be obsessed
with folding things. We present a mathematical approach to “rigid folding” inspired by the way atomistic
structures form naturally. Their characteristic features in molecular science imply desirable features for
macroscopic structures, especially 4D structures that deform. Origami structures, in turn, suggest an
unusual way to look at the Periodic Table.


Richard D. James is Distinguished McKnight University Professor at the University of Minnesota. He has a Sc.B. in Engineering from Brown University and a Ph.D. in Mechanical Engineering from the Johns Hopkins University. He has authored or co-authored 150 articles, has given 50 plenary or named lectureships, and was awarded the Humboldt Senior Research Award (2006/7), the Warner T. Koiter Medal from ASME (2008), the William Prager Medal from the Society of Engineering Science (2008), the Brown Engineering Alumni Medal (2009) and the Theodore von Karman prize from SIAM (2014). James’ current research concerns the study of “Objective Structures”, a mathematical way of looking at the structure of matter, the hysteresis and reversibility of solid-solid phase transformations, and the direct conversion of heat to electricity using transformations in multiferroic materials.

October 26 (Friday): MEAM Special Seminar

Roger T. Howe, William E. Ayer Professor of Engineering, Stanford University

"Broad-Spectrum Electronic Biomolecular Sensing"

3:00 p.m., Wu and Chen Auditorium, Levine Hall


Conventional electronic biomolecular sensors use charge transfer across an electrically biased electrode-electrolyte interface as the detection mechanism. Specificity to a single analyte molecule is possible by functionalizing the electrode with an engineered protein. Recent research at Stanford [1,2] has introduced a new type of electronic biomolecular sensor, in which the interface is designed to transduce information about intra-molecular bond vibrational frequencies of non-redox active molecular species. This information can be observed in the tunneling current vs. voltage signature across a nanoscale electro-chemical interface, if (i) it is designed to operate between the adiabatic and non-adiabatic charge-transfer regimes and (ii) the current is measured using an ultralow noise potentiostat.

In this talk, I will first discuss the design guidelines for the nanoscale electrochemical interface, which are derived from a circuit model based on a quantum mechanical analysis of the intermediate tunneling regime. For the initial demonstration of the nanoscale sensing interface, serial prototyping techniques (e.g., focused ion beam etching) were utilized. Current vs. voltage scans demonstrate the operating regimes of the interface and its ability to detect subtle differences in analytes, such as leucine and 2-d leucine, the latter having a single substitution of H with D. In conclusion, I will describe the pattern recognition strategy to quantify the concentration of the neurotoxin BoNT-A in human serum.

1. C. Gupta, et al., “Active control of probability amplitudes in a mesoscale system via feedback-induced suppression of dissipation and noise,” J. Appl. Phys., 120, 224902 (2016).
2. C. Gupta, et al., “Quantum Tunneling Currents in a Nanoengineered Electrochemical System,” J. Phys. Chem. C, 121, 15085–15105 (2017).


Roger T. Howe is the William E. Ayer Professor in the Dept. of Electrical Engineering at Stanford University. He received a B.S. in physics from Harvey Mudd College in 1979 and an M.S. and Ph.D. in electrical engineering from the University of California, Berkeley in 1981 and 1984. After faculty positions at CMU and MIT from 1984 – 1987, he returned to Berkeley where he was a Professor until 2005. His research group focuses on nanoscale system design and fabrication for a variety of applications. He was the Faculty Director of the Stanford Nanofabrication Facility from 2009 – 2017 was Director of the NSF’s National Nanotechnology Infrastructure Network (NNIN) from 2011 – 2015. In 2016, he co-founded ProbiusDx, Inc. to commercialize the research in his group on a broad-spectrum biomolecular sensor.


October 29 (Monday): MEAM Ph.D. Seminar

Lisa Mariani, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Kevin Turner

"Mechanical Characterization of Printed Cellulose Nanofibril Thin Films"

4:00 p.m., Room 337, Towne Building


Cellulose nanofibrils (CNFs) are a naturally abundant polymer derived from trees and are an attractive engineering material because of their exceptionally high specific stiffness and strength, high aspect ratio (>100), optical transparency, and biodegradability. Traditional techniques to prepare nanopapers from aqueous suspensions comprised of low volume fractions of CNFs via dish drying, oven drying, and vacuum filtration yield materials with moduli on the order of 10 GPa, but have long processing times and are limited to thicknesses less than 70 μm. This study uses printing and subsequent drying processes to prepare neat CNF thin films with greatly reduced manufacturing times because of the layer-by-layer process. The surfaces and mechanical properties of the thin films are characterized using stylus profilometry, atomic force microscopy (AFM), nanoindentation, and tensile testing with digital image correlation to measure the strains. The orientation of the CNF fibers is determined via polarized light microscopy and AFM, which reveal that alignment can be induced through the movement of drying fronts. The alignment of CNFs is demonstrated to result in enhanced mechanical properties. This work shows a method to prepare neat CNF thin films with controlled alignment, which reveals the potential to improve mechanical properties.

October 30

Nicholas Zabaras, Viola D. Hank Professor of Computational Science and Engineering, Department of Aerospace and Mechanical Engineering, Notre Dame University

"Bayesian Deep Learning for Predictive Scientific Computing"


We will briefly review recent advances in the solution of stochastic PDEs using Bayesian deep encoder-decoder networks. These models have been shown to work remarkably well for uncertainty quantification tasks in very-high dimensions. In this talk through examples in computational physics and chemistry, we will address their potential impact for modeling dynamic multiphase flow problems, accounting for model form uncertainty in coarse grained RANS simulations and providing the means to coarse graining in atomistic models. Emphasis will be given to the small data domain using Bayesian approaches. The training of the network is performed using Stein variational gradient descent. We will show both the predictive nature of these models as well as their ability to capture output uncertainties induced by the random input, limited data and model error. In closing, we will outline the integration of these surrogate models with generative adversarial networks for the solution of inverse problems.


Prof. Nicholas Zabaras joined Notre Dame in 2016 as the Viola D. Hank Professor of Computational Science and Engineering after serving as Uncertainty Quantification Chair and founding director of the “Warwick Centre for Predictive Modeling (WCPM)” at the University of Warwick. He is the Director of the interdisciplinary University of Notre Dame “Center for Informatics and Computational Science (CICS)” that aims to bridge the areas of data-sciences, scientific computing and uncertainty quantification for complex multiscale/multiphysics problems in science and engineering. He was also the Hans Fisher Senior Fellow with the Institute for Advanced Study at the Technical University of Munich where he is currently serving as "TUM Ambassador". He is also an Honorary Professor at the Dept. of Mathematics at the University of Hong Kong. Prior to this, he spent 23 years serving in all academic ranks of the faculty at Cornell University where he was the director of the “Materials Process Design and Control Laboratory (MPDC)”. He received his Ph.D. in Theoretical and Applied Mechanics from Cornell, after which he started his academic career at the faculty of the University of Minnesota. Professor Zabaras' research focuses on the integration of computational mathematics, statistics, and scientific computing for the predictive modeling of complex systems. He has been honored with the Wolfson Research Merit Award from the Royal Society, the Michael Tien '72 Excellence in Teaching Prize from Cornell University, and the Presidential Young Investigator Award from the National Science Foundation.

November 5 (Monday): MEAM Ph.D. Thesis Defense

Sarah Tang, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Vijay Kumar

“Control, Planning, and Coordination for Dynamic Aerial Manipulation with Robot Teams”

11:00 a.m., Room 307, Levine Hall


The rapid and safe transportation of suspended payloads with aerial vehicles is a crucial task across a breadth of industries, from construction to cargo delivery to agriculture to first response. As opposed to carrying payloads against vehicles' bodies, manipulating payloads via a cable suspension allows the vehicle retain its agility and interact with objects from a distance. This problem has been studied for a variety of unmanned aerial vehicles (UAVs), including fixed-wing, helicopter, and quadrotor systems, in single- and multi-robot contexts.

This work proposes techniques for dynamic manipulation of slung-loads---execution of maneuvers where the payload swings significantly---with aerial robots. It begins by examining challenges associated with nonlinear geometric control of suspended-payload systems. We then examine trajectory generation algorithms for a single quadrotor carrying a payload through obstacle-filled environments. In allowing the system to exploit its entire range of motion, more energy-optimal load transport and, more importantly, navigation of obstacles infeasible for swing-free systems can be achieved. Finally, we propose a safe, scalable, and complete algorithm that generates trajectories for a multi-robot team in which each agent is transporting a single payload, but are coordinated such that vehicles retain their abilities for dynamic manipulation.

November 6

Yu Sun, Canada Research Chair in Micro and Nano Engineering Systems and Professor, Department of Mechanical Engineering, University of Toronto

"Medical Robotics: Manipulation of Cells and Intracellular Structures"


Advances in biology and medicine require enabling instruments and techniques for manipulating and characterizing cells and sub-cellular structures. Cell surgery and automated biophysical characterization of cells enable new frontiers in science and have tangible clinical relevance. Precise extraction of chromatins and sub-cellular organelles is poised to revolutionize genomics and proteomics. Deposition of foreign materials into cells is enabling new drug efficacy tests for the pharmaceutical industry. In this talk, I will provide an overview of robotic cell manipulation by introducing the brief history and background of the field; examples of cell manipulation tasks; techniques for sensing, actuation, and control; and toolsets and systems. Technical challenges such as using 2D microscopy visual feedback to obtain 3D depth information, path planning for the manipulation of deformable cells with minimal cell deformation, and feedback control at sub-micrometer, sub-nanoliter, and sub-nanoNewton levels will be discussed. I will then use one of our recent projects on robotic manipulation of cardiomyocytes as an example to explain how robotic cell manipulation can enable personalized medicine. Finally, I will introduce the progress we have made in ‘Intracellular Fantastic Voyage’ for robotic navigation inside a cell and physical measurement of intracellular structures.


Yu Sun is a Professor in the Department of Mechanical and Industrial Engineering, with joint appointments in the Institute of Biomaterials and Biomedical Engineering and the Department of Electrical and Computer Engineering at the University of Toronto. He was elected Fellow of ASME (American Society of Mechanical Engineers), IEEE (Institute of Electrical and Electronics Engineers), AAAS (American Association for the Advancement of Science), and CAE (Canadian Academy of Engineering) for his work on micro-nano devices and robotic systems. His Advanced Micro and Nanosystems Laboratory specializes in developing innovative technologies and instruments for manipulating and characterizing cells, molecules, and nanomaterials, and works with an extensive collaborative network that includes clinician scientists, industry partners, biologists, physicists, material scientists, and engineers.

Sun obtained his Ph.D. from the University of Minnesota in 2003 and did his postdoctoral research at ETH-Zürich. In 2004, Sun joined the University of Toronto where he is presently a McLean Senior Faculty Fellow and a Tier I Canada Research Chair. In 2012-2013, he directed the University Nanofabrication Center as the faculty director. Sun has served and serves on the editorial boards of IEEE Trans. Robotics, IEEE Trans. Automation Science and Engineering, IEEE Trans. Mechatronics, J. Micromechanics Microengineering, Sensors and Actuators A: Physical, Scientific Reports, and Microsystems & Nanoengineering. Among the awards he received were the IEEE Robotics and Automation Society Early Career Award; over a dozen best paper awards and finalists at major international conferences; six times University of Toronto Connaught Innovation Award; the McLean Award; the First Prize in Technical Achievement of ASRM (American Society for Reproductive Medicine); an NSERC E.W.R. Steacie Memorial Fellowship; and the IEEE C.C. Gotlieb Computer Award.

November 7 (Wednesday): MEAM Ph.D. Thesis Defense

Ruiyuan Ma, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Jennifer Lukes

"Examination of Callaway-Holland-Based Thermal Conductivity Calculation for Nano-Phononic Crystals"

3:30 p.m., Room 307, Levine Hall


Phononic crystals are periodically structured materials whose frequency spectrum is characterized by band gaps, regions in frequency space where acoustic or elastic waves cannot propagate. Nanoscale phononic crystals have shown promise for reducing thermal conductivity and improving the thermoelectric figure of merit. Correctly calculating the thermal conductivity of nano phononic crystals has become increasingly important due to the growing research interests in the thermal properties of these materials. A widely used expression to calculate thermal conductivity, presented by Klemens and expressed in terms of the relaxation time by Callaway and Holland, originates from the Boltzmann transport equation. In common practice, the expression is simplified by three assumptions which were first applied in bulk materials: the isotropic thermal conductivity assumption; the empirical relaxation time assumption; and the effective material assumption. In this work, we will examine those assumptions of Callaway-Holland-based models for nano-phononic crystals. This talk will first examine the isotropic assumption by calculating the thermal conductivities of bulk Si, Si/Ge superlattices, and Si/Ge quantum dot superlattices (QDSL) using both the isotropic assumption and direct summation methods. The direct summation method has been proved to give more accurate results. We will then examine the empirical phonon relaxation time assumption by comparing the Callaway-Holland model to molecular dynamics-based Normal Mode Analysis method. The fundamental reasons behind the difference between the empirical method and the NMA method will be revealed. Finally, the effective material assumption will be briefly examined by using Green Kubo Modal Analysis method. Overall, this talk will provide direction in the correct thermal conductivity calculation for nano-phononic crystals.

November 13: MEAM Career Development Series Seminar

Thomas Cassel, Practice Professor, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania

"What Employers Really Want To Learn From Your Interview"


For this seminar on job interviewing, Dr. Tom Cassel will draw upon insights from his 20-year business career prior to joining Penn’s faculty, as well as from helpful resources available at Penn’s Career Services, and from interviewing advice from regional technology and consulting firms. Topics of discussion will include preparing for the interview, dress and behavior during the interview, what to expect with respect to interview formats and questions, what interviewers are looking for, how to leave a good impression, following up after the interview, and negotiating the job offer.


Dr. Tom Cassel joined Penn’s faculty in 1999 following a 20-year career of entrepreneurial business leadership. As Professor of Practice, he serves as Director of the Penn’s Engineering Entrepreneurship Program. Prior to joining Penn, Dr. Cassel had been a co-founder, chairman and CEO of Reading Energy Holdings, Inc. This privately-held company developed independent power plants in California, Pennsylvania and Illinois having an aggregate capital cost exceeding $600 million. Each of the plants represented a significant advancement in the state of the art of power plant environmental design. Moreover, they created hundreds of new employment opportunities and enhanced the economies of their host communities. Apropos of this seminar, Dr. Cassel interviewed and hired numerous employees during this 20-year business career.

Dr. Cassel received his BS, MS and PhD degrees from the University of Pennsylvania and has studied at Harvard Business School. He is widely published, has addressed numerous conferences and hearings, and has appeared on both radio and television. He has received Penn’s highest awards for distinguished teaching and advising. He is an advisor to several high-tech start-up ventures and has been active with several non-profit organizations.

November 19 (Monday): MEAM Ph.D. Thesis Defense

Paul Barclay, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Jennifer Lukes

"Condensation and Mobility Studies of Fluid Interfaces "

10:00 a.m., Room 2C6, DRLB


Condensation is of central importance in a broad range of areas in nature and industry. Aerosol-cloud interactions, a currently a significant open question in climate modeling, and water harvesting mechanisms on organisms such as cacti, beetles, and spiders, are natural processes that are rely on condensation. Condensation is an effective method for transferring heat due to the latent heat required for a fluid to change phase from a gas to a liquid. Improvements in condensation processes would have an impact in a variety of industrial areas such as thermal management, environmental control, microelectronics, desalination, and power generation. Dropwise condensation is preferable over filmwise condensation because it has a significantly higher heat transfer coefficient. Nanopatterned surfaces are of interest because they have experimentally demonstrated higher heat transfer than their smooth counterparts, but recent heat transfer measurements on individual droplets have revealed discrepancies between theoretical predictions and experimental measurements for the smallest droplets. Interfacial properties on small length scales are often difficult to measure experimentally and are often used as fitting parameters in condensation models. The common assumptions used when modeling dropwise condensation are that (1) the condensing droplets are thermodynamically quasi-static and that (2) the heat and mass transport are uncoupled, that is, droplet motion and heat transfer are modeled independently of one another. In this dissertation, several continuum properties including the mass accommodation coefficient and interfacial mobility are computed allowing for the physical parameters to be known a priori for continuum scale models such as the Navier-Stokes-Cahn-Hilliard equations or interfacial resistances in condensation models. Furthermore, the two fundamental assumptions used in condensation models are examined in an attempt to resolve the theoretical and experimental discrepancies. This will be done by leveraging microscopic and non-equilibrium thermodynamic approaches to determine the validity of the condensation assumptions for planar and highly curved systems.

November 20

Chris Fang-yen, Associate Professor of Bioengineering and Neuroscience, University of Pennsylvania

"Aging and Automation in a Model Roundworm"

10:45 a.m., Glandt Forum, Singh Center for Nanotechnology


How do organisms grow old? Aging, once thought to be a passive wear-and-tear process, is now known to be actively regulated by genetic factors. The microscopic nematode C. elegans, with its short (2-week) lifespan and genetic manipulability, has been a critical model for discovering the basic mechanisms underlying aging. Classic assays of worm aging depend on tedious and low-throughput manual observation and have been largely limited to measurement of lifespan, without information about individual health trajectories. I describe several microfabrication and automation technologies to generate high-throughput and longitudinal analyses of behavior of C. elegans during its entire lifespan. We are using these tools to screen for genetic and pharmacological perturbations that affect aging.


Dr. Fang-yen's laboratory explores how neural circuits generate behavior using the nematode C. elegans as a model. This 1-mm-long worm has only 302 neurons, and is the only animal for which the complete 'wiring diagram' of synaptic connectivity has been determined. This relative simplicity of the worm's nervous system, as well as its genetic manipulability and optical transparency, make it a unique model for understanding the neuronal basis of coordinated behavior. The laboratory adopts a multidisciplinary approach, applying and integrating tools from fields such as optics, molecular biology, microfluidics, and machine learning. In particular, Dr. Fang-yen and his collaborators have recently developed a closed-loop system for optogenetic spatiotemporal control of neural activity in freely moving animals. He is also broadly interested in creating new tools for neuroscience and bioimaging. Dr. Fang-yen obtained his Ph.D. in Physics at the Massachusetts Institute of Technology in 2002.

November 27


December 4

Portonovo S. Ayyaswamy, Asa Whitney Professor of Dynamical Engineering, University of Pennsylvania

"Multiscale Modeling of Nanoparticle Transport: Applications to Targeted Drug Delivery"


This talk will describe methods based on Equilibrium and Non-Equilibrium Statistical Mechanics to construct numerical procedures that enable predictive models for nanoparticle transport. Formulations for the Fluctuating Hydrodynamics approach, the Generalized Langevin Model, the Hybrid method, and the Deterministic method will be provided. Various length and time scales of relevance will be discussed. The models described here have particular applications to targeted drug delivery employing nano sized carriers. The nano particle shape considered here is either spherical or elliptical. Predictions from the simulations of the models are validated by comparison with experimental data where available.


Dr. Ayyaswamy's research is in the area of mechanical engineering, with foci in modeling, simulations and experimentation of multi-phase flow/heat and mass transfer. His latest research activities are concerned with the motion of nanoparticles and associated transport, particularly in the context of targeted drug delivery. Over the years, Dr. Ayyaswamy has contributed to many diverse areas of heat transfer, mass transfer, and fluid mechanics. These include investigations of: finite sized bubble motion and the effects of surfactants in the context of gas embolism, forced convective effects on condensation, evaporation and combustion of moving drops and particles, the effect of electric fields on flames under normal and microgravity conditions, capillary flows related to heat pipes, and buoyancy driven flows. In the area of interconnection of electronic chips by wire bonding, he has investigated the melting of metals and alloys by low-energy plasma arc-discharges and subsequent solidification. In the area of die-bonding, he and his coworkers have established new results for the squeezing flow of yield stress fluids. In the area of microgravity fluid mechanics, mass transfer, and biotechnology, his lab has worked to determine the mechanisms responsible for changes in osteoblast behavior under simulated microgravity conditions by employing experimental and numerical-analytical methods. He has also made fundamental contributions to the understanding of buoyancy driven flows in enclosures.

December 20 (Thursday): MEAM Ph.D. Thesis Defense

Zac Milne, Ph.D. Candidate, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
Advisor: Robert Carpick

"The Role of Sliding Contact in Nanoscale Tribochemistry"

8:00 a.m., Towne 227 (MEAM Conference Room)


In this thesis, the results of experimental and theoretical studies exploring friction and adhesion at the nanoscale are presented. Using a customized in situ transmission electron microscopy nanoindentation methodology, it is observed that cohesion of silicon and adhesion of silicon and diamond are strongly modified by the sliding speed and the normal stress applied during sliding. This indicates that shear stress modulates the reactivity of the surfaces. This is the first time that tunable adhesion of hard contacts has been demonstrated in situ.

If sliding experiments are performed in ultra-high vacuum and the interfacial shear stress is low enough to avoid surface modification, the multibond model of friction predicts that adhesion will decrease with increasing sliding speed in experiments with simultaneous sliding and retraction. Results from sliding of nanoscale silica asperities against highly-oriented pyrolytic graphite (HOPG) and hydrogen-doped tetrahedral amorphous carbon (aCH) surfaces are consistent with this model. This contrasts with the directly-proportional adhesion-speed behavior observed in the in situ transmission electron microscopy experiments of silicon and diamond.

When the number of available bonding sites increases with stress and speed, adhesion will increase. This is the case for the silicon-silicon and silicon-diamond work. However, if the number of available sites is constant, sliding faster will further reduce adhesion. This is the case of the work of silica sliding against HOPG and aCH.

Existing popular reduced order models for friction, the Prandtl-Tomlinson with Temperature model and the multibond model, are frequently used to explain the observed nanoscale phenomena of friction increasing logarithmically with sliding speed. However, both models contain overgeneralizing or unphysical assumptions. A new model, the modified multibond model, was developed and is consistent with experimental results. This dissertation provides strong evidence that damping is a critical parameter and that the Fokker-Planck equation is more suitable to describe friction-speed behavior than the Prandtl-Tomlinson with Temperature and multibond models. The modified multibond model also predicts the decrease of adhesion with increasing speed observed experimentally in the silica-HOPG and silica aCH experiments.

December 20 (Thursday): MEAM Special Seminar

Masahiro Narasaki, Ph.D. Candidate, Kyushu University

"Thermal Transport in Structurally-Modified Nanocarbon Materials: Studies on Carbon Nanotube, Carbon Nanofiber, and Graphene"

11:00 a.m., Room 337, Towne Building


This talk mainly describes experimental studies on thermal transport in a structurally-modified individual multi-walled carbon nanotube, carbon nanofiber, and single-layer graphene. Although the thermal properties of pristine nanocarbon materials are well studied, effects of size, defects, and chemical modification on the thermal properties are still veiled because of experimental difficulties to realize both thermal measurement and structural modification. In this work, an individual multi-walled carbon nanotube and carbon nanofiber were irradiated with a focused ion beam to induce defects and control the phonon-scattering lengths, and a single-layer graphene was fluorinated. All the samples were suspended on a metallic-thin-film sensor to measure their thermal conductivities. The sensor is fabricated by MEMS techniques and works as a resistance thermometer. Effects of size and fluorination on the thermal conductivities are discussed. Lastly, molecular dynamics is utilized to study the thermal transport in single-layer graphene. This work will be useful for applications in future thermal designs and development of nanocarbon materials for transistors and heat spreaders.


Mr. Masahiro Narasaki is a doctoral candidate in the Department of Aeronautics and Astronautics at Kyushu University in Japan. He has been advised by Dr. Koji Takahashi since 2014. Professor Takahashi’s research interests include studies on thermal transport in nanomaterials, carbon nanotubes, graphene and nano-fluidics such as nano-bubbles at solid-liquid interfaces and observation of liquid in a carbon nanotube. Masahiro also has experience as a research assistant at International Institute for Carbon-Neutral Energy Research from 2016 to 2018. Since 2018 he has been on a research fellowship for young scientists of Japan Society for Promotion of Science (JSPS). Mr. Narasaki is currently a visiting student being advised by Dr. Jennifer Lukes, a Mechanical Engineering and Applied Mechanics professor at University of Pennsylvania. The Lukes Group research interest includes studies of thermal phenomena, mass transport, and emergent effects on fluids, superlattices, nanocomposites, and other new materials. Masahiro collaboration with Professor Lukes is focused on molecular dynamics studies on thermal conduction in graphene, sponsored by the JSPS overseas challenge program for young researchers.