MEAM Seminar Series Spring 2019

For Fall 2018 Seminars, click here.

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

To be added to the MEAM Events mailing list (which sends notifications regarding all departmental seminars and events) please email us at meam-events@lists.seas.upenn.edu.

January 3 (Thursday): MEAM PhD Seminar

Luis Guerrero Bonilla, Ph.D. Candidate, University of Pennsylvania
Advisor: Vijay Kumar

"Resiliant Formations of Robots"

10:00 a.m., Room 337, Towne Building

Abstract:

The consensus algorithm has many applications in robotics related to distributed decision making. In a group of robots, the success of the algorithm depends on each robot sharing the appropriate information with its neighbors. When some robots do not follow the proper algorithm, the consensus can be impeded or manipulated. In this talk, I present result that allow formations of robots to achieve consensus despite the presence of malicious robots, making them resilient to robot malfunctions or adversarial behavior.

January 15: MEAM/GRASP Seminar

Pierre E. Dupont, Edward P. Marram Chair and Chief of Pediatric Cardiac Bioengineering, Boston Children's Hospital, and
Professor of Surgery, Harvard School of Medicine

"Stretching the Boundaries of Medical Robotics"

Abstract:

My lab creates medical robots not only for minimally invasive surgery, but also for targeted drug delivery and for tissue regeneration. This talk will describe three of our technologies. The first consists of tetherless robots that are powered, controlled and imaged using an MRI scanner. These devices vary from patient-mounted needle-driving robots to capsules that can move inside fluid-filled body lumens. The second technology consists of a class of robot implants designed to apply traction forces over a period of weeks inside the body so as to induce the regeneration of soft tissues. Applications include lengthening the esophagus and bowel for the treatment of congenital defects and disease. The third is a type of continuum robot that is based on concentrically combining pre-curved superelastic tubes. We are using this technology to create multi-armed systems for intracranial endoscopic surgery. We are also developing endoscopically-guided catheters that can navigate autonomously inside the blood-filled beating heart.

Biography:

Pierre E. Dupont is Chief of Pediatric Cardiac Bioengineering and holder of the Edward P. Marram Chair at Boston Children’s Hospital. He is also a Professor of Surgery at Harvard Medical School. His research group develops robotic instrumentation and imaging technology for medical applications. He received the BS, MS and PhD degrees in Mechanical Engineering from Rensselaer Polytechnic Institute, Troy, NY, USA. After graduation, he was a Postdoctoral Fellow in the School of Engineering and Applied Sciences at Harvard University, Cambridge, MA, USA. He subsequently moved to Boston University, Boston, MA, USA where he was a Professor of Mechanical Engineering and Biomedical Engineering. He is an IEEE Fellow, a Senior Editor for the IEEE Transactions on Robotics and a member of the Advisory Board for Science Robotics.

January 22

Douglas J. Jerolmack, Professor of Earth and Environmental Sciences, University of Pennsylvania

"Viewing Earth's Surface as a Soft Matter Landscape"

Abstract:

The Earth's surface is composed of a staggering diversity of particulate-fluid mixtures: dry to wet, dilute to dense, colloidal to granular, attractive to repulsive particles, laminar to turbulent flows, and steady to highly-unsteady forcing. This material variety is matched by the range of relevant stresses and strain rates, from rapid and catastrophic landslides to the slow relaxation of soil over geologic timescales. In this talk I illustrate the commonalities and challenges in understanding geophysical flows by highlighting two problems: gravity-driven downslope soil movement, and fluid-driven particle transport in rivers.

Soil on hillslopes slowly and imperceptibly creeps downhill, but suddenly liquefies to produce landslides. The transition between creeping and flowing is a yield condition, often defined in terms of the shear stress, that depends on the characteristics of the soil and the geologic environment. We show that the nature of this transition, however, is general. Creep is the localized and erratic motion of soil grains below yield; because this kind of fragility is a generic consequence of disorder, soil creep should be similar to amorphous glass. Indeed, we find that the transition from creeping to landsliding is a continuous phase transition that follows predictions from glass transition models. The generality of this transition suggests that the onset of sediment transport in rivers should behave in a similar manner, and we demonstrate that this is the case using laboratory experiments and simulations. Because the sediment transport rate rapidly increases for stresses above yield, many landscapes such as rivers organize to be close to the yield point. In essence, landscapes flicker back and forth across the glass transition. We explore several consequences of these dynamics for the sculpting of landscapes.

Biography:

Doug Jerolmack is Professor and Graduate Chair in Earth and Environmental Science, with a secondary appointment in Mechanical Engineering and Applied Mechanics, at the University of Pennsylvania. His area of study is experimental geophysics, with a focus on geomorphology (the "science of scenery"). Dr. Jerolmack studies the spatial and temporal evolution of patterns that emerge at the interface of fluid and sediment on Earth and planetary surfaces. His group uses laboratory experiments, combined with field work and theory, to elucidate the minimum number of ingredients that are required to explain physical phenomena. Particular foci include: granular physics of fluid-driven (water and wind) sediment transport; landform dynamics including dunes, river channels, deltas and fans; stochastic and nonlinear transport processes; and landscape response to dynamic boundary conditions such as climate. He received a B.S. in Environmental Engineering at Drexel University in 2001, PhD in Geophysics from MIT in 2006, and was a postdoctoral researcher at the Saint Anthony Falls Lab at University of Minnesota 2006-2007. He has been at Penn since 2007.

January 25 (Friday): MEAM/GRASP Seminar

Howie Choset, Kavcic-Moura Professor of Computer Science, Carnegie Mellon University

"Geometric Biologically Inspired Robots that Span Industries from Medical to Manufacturing"

11:00 a.m., Wu and Chen Auditorium, Levine Hall

Abstract:

The animal kingdom is full of both human and non-human animals worthy of investigation, emulation and re-creation. As such, my research group has created a comprehensive research program focusing on biologically-inspired robots, and has applied them to search and rescue, minimally invasive surgery, and manufacturing. These robots inspire great scientific challenges in mechanism design, control, planning and estimation theory. These research topics are important because once the robot is built (design), it must decide where to go (path planning), determine how to get there (control), and use feedback to close the loop (estimation). A common theme to these research foci is devising ways by which we can reduce multi-dimensional problems to low dimensional ones for planning, analysis, and optimization. In this talk, I will discuss our results in geometric mechanics, Bayesian filtering, and scalable multi-agent planning to support these reductions. This talk will also cover how my students and I commercialized these technologies by founding three companies: Medrobotics, Hebi Robotics, and Bito Robotics. In 2015, the surgical snake robot from Medrobotics cleared the FDA and has begun to democratize the delivery of medical care in the US and Europe If time permits, I will also discuss my educational activities, especially at the undergraduate level, with a course using LEGO robots, and the role of entrepreneurism in University education.

Biography:

Howie Choset is the Kavcic-Moura Professor of Computer Science in the Robotics Institute at Carnegie Mellon University. Howie started his robotics career in the GRASP Lab and today, he serves as the co-director of the Biorobotics Lab and as director of the undergraduate Robotics Major. Howie’s research group reduces complicated high-dimensional problems found in robotics to low-dimensional simpler ones for design, analysis, and planning. Motivated by applications in confined spaces, Choset has created a comprehensive program in modular, high DOF, and multi- robot systems, which has led to basic research in mechanism design, path planning, motion planning, and estimation. This work has contributed to strategically significant problems in diverse areas such as surgery, manufacturing, infrastructure inspection, and search and rescue. In addition to publications, this work has led to Choset, along with his students, to form several companies including Medrobotics, for surgical systems, Hebi Robotics, for modular robots, and Bito Robotics for autonomous guided vehicles. In 2015, Choset’s surgical snake robot cleared the FDA and has been in use in the US and Europe since. In 2017, Choset co-lead the formation of the Advanced Robotics for Manufacturing Institute, which is $250MM national institute advancing both technology development and education for robotics in manufacturing. Finally, Choset is a founding Editor of the journal Science Robotics.

January 29

Robert Shepherd, Assistant Professor, Sibley School of Mechanical and Aerospace Engineering, Cornell University

"Elastomeric Materials for Autonomic Force Transmission, Optoelectronic Sensing, and 3D Printing Soft Robots"

Abstract:

This talk will present multidisciplinary work from material composites and robotics. We have created new types of actuators, sensors, displays, and additive manufacturing techniques for soft robots and haptic interfaces. For example, we now use stretchable optical waveguides as sensors for high accuracy, repeatability, and material compatibility with soft actuators. For displaying information, we have created stretchable, elastomeric light emitting displays as well as texture morphing skins for soft robots. We have created a new type of soft actuator based on molding of foams, and stereolithography printing of elastomer based soft robots, and implemented deep learning in stretchable membranes for interpreting touch. All of these technologies depend on the iterative and complex feedback between material and mechanical design. I will describe this process, what is the present state of the art, and future opportunities for science in the space of additive manufacturing of elastomeric robots.

Biography:

Rob Shepherd is an associate professor at Cornell University’s Organic Robotics Lab (ORL), which focuses on using synthetic adaptation of natural physiology to improve machine function and autonomy. Our research spans three primary areas: bioinspired robotics, haptic interfaces, soft sensors and displays, and advanced manufacturing. We use soft materials, mechanical design, and novel fabrication methods to replicate sensory organs such as dermal papillae, replicate organs that rely on actuation such as the heart, and to power soft actuators and robots. He is the recent recipient of an Air Force Office of Scientific Research Young Investigator Award, and an Office of Naval Research Young Investigator Award. His work has been featured in popular media outlets such as the BBC, Discovery Channel, and PBS’s NOVA science documentary series.

February 5

Anette Peko Hosoi, Neil and Jane Pappalardo Professor of Mechanical Engineering, Massachusetts Institute of Technology

"Hairy Hydrodynamics"

Abstract:

Flexible slender structures in flow are everywhere. While a great deal is known about individual flexible fibers interacting with fluids, considerably less work has been done on fiber ensembles — such as fur or hair — in flow. These hairy surfaces are abundant in nature and perform multiple functions from thermal regulation to water harvesting to sensing. Motivated by these biological systems, we consider several examples of hairy surfaces interacting with flow including drinking bats and diving sea otters. In the first example we consider viscous dipping, a feeding method utilized by many nectar drinking animals. This mechanism is reminiscent of Landau-Levich-Derjaguin (LLD) dip coating, and has been analyzed through the LLD framework in previous studies. However, many viscous dippers have hairy structures on their tongues that enhance fluid uptake. In this study, we investigate the impact of mesoscale hairy structures on feeding efficiency. In the second example, we take inspiration from semi-aquatic mammals (such as fur seals, otters, and beavers) which have specially adapted fur that serves as an effective insulator both above and below water. Many of these animals have evolved pelts that naturally entrap air when they dive. Here we investigate diving conditions and fur properties which amplify air entrainment.

Biography:

Peko Hosoi is the Neil and Jane Pappalardo Professor of Mechanical Engineering and professor of Mathematics at MIT and Associate Dean of the School of Engineering. Her research contributions lie at the junction of nonlinear hydrodynamics, biomechanics, and bio-inspired design. A common theme in her work is the fundamental study of shape, kinematic, and rheological optimization of biological systems with applications to the emergent field of “soft robotics.” Her work is internationally respected by physicists, biologists, roboticists, applied mathematicians, and engineers alike, and is used to guide the engineering design of robotic swimmers, crawlers, burrowers, and other mechanisms. More recently, she has turned her attention to problems that lie intersection of biomechanics, applied mathematics, and sports. She is the co-founder of the MIT Sports Lab which aims to solve engineering challenges in the sports domain. The program connects students and faculty with alumni and industry partners who work together to improve athletic performance using engineering to elevate endurance, speed, accuracy, and agility.

Peko has received numerous awards including the APS Stanley Corrsin Award, the Ruth and Joel Spira Award for Distinguished Teaching, the Bose Award for Excellence in Teaching, and the Jacob P. Den Hartog Distinguished Educator Award. She is a Fellow of the American Physical Society (APS), a Radcliffe Institute Fellow, and a MacVicar Faculty Fellow.

Peko joined the Department of Mechanical Engineering in 2002 as an assistant professor after receiving an AB in physics from Princeton University and an MA and PhD in physics from the University of Chicago. She was promoted to full professor in 2013.

February 12

Charles Meneveau, Louis M. Sardella Professor of Mechanical Engineering, Johns Hopkins University

"Fluid Mechanics and Turbulence in Extended Wind Farms"

Abstract:

In this presentation we discuss several properties of the flow structure and turbulence in the wind turbine array boundary layer (WTABL). This particular type of shear flow develops when the atmospheric boundary layer interacts with an array of large wind turbines. Based on such understanding, we aim to develop reduced order, analytically tractable models. These are important engineering tools for wind energy, both for design and control purposes. We will focus on two fluid mechanical themes relevant to wind farm design and control. The first topic deals with spectral characteristics of the fluctuations in power generated by an array of wind turbines in a wind farm. We show that modeling of the spatio-temporal structure of canonical turbulent boundary layers coupled with variants of the Kraichnan’s random sweeping hypothesis can be used to develop analytical predictions of the frequency spectrum of power fluctuations of wind farms. In the second part we describe a simple (deterministic) dynamic wake model, its use for wind farm control, and its extension to the case of yawed wind turbines. The work to be presented arose from collaborations with Juliaan Bossuyt, Johan Meyers, Richard Stevens, Tony Martinez, Michael Wilczek, Carl Shapiro and Dennice Gayme. We are grateful for National Science Foundation support.

Biography:

Charles Meneveau is the Louis M. Sardella Professor in the Department of Mechanical Engineering and is Associate Director of the Institute for Data Intensive Engineering and Science (IDIES) at Hopkins. He received his B.S. degree in Mechanical Engineering from the Universidad Técnica Federico Santa María in Valparaíso, Chile, in 1985 and M.S, M.Phil. and Ph.D. degrees from Yale University in 1987, 1988 and 1989, respectively. During 1989/90 he was a postdoctoral fellow at the Center for Turbulence Research at Stanford. He has been on the Johns Hopkins faculty since 1990. His area of research is focused on understanding and modeling hydrodynamic turbulence, and complexity in fluid mechanics in general. The insights that have emerged from Professor Meneveau’s work have led to new numerical models for Large Eddy Simulations (LES) and applications in engineering and environmental flows, including wind farms. He also focuses on developing methods to share the very large data sets that arise in computational fluid dynamics. He is Deputy Editor of the Journal of Fluid Mechanics and has served as the Editor-in-Chief of the Journal of Turbulence. Professor Meneveau is a member of the US National Academy of Engineering, a foreign corresponding member of the Chilean Academy of Sciences, a Fellow of APS, ASME, AMS and recipient of the Stanley Corrsin Award from the APS, the JHU Alumni Association's Excellence in Teaching Award, and the APS' François N. Frenkiel Award for Fluid Mechanics.

February 15 (Friday): MEAM Ph.D. Thesis Defense

Monroe D. Kennedy III, Ph.D. Candidate, University of Pennsylvania
Advisor: Vijay Kumar

"Modeling and Control for Robotic Assistants: Single and Multi-Robot Manipulation"

12:00 p.m., East Conference Room 303, Pennovation Center, 3rd Floor (PERCH)

Abstract:

As advances are made in robotic hardware, the capacity of the complexity of tasks they are capable of performing also increases. One goal of modern robotics is to introduce robotic platforms that require very little augmentation of their environments to be effective and robust. Therefore the challenge for the Roboticist is to develop algorithms and control strategies that leverage knowledge of the task while retaining the ability to be adaptive, adjusting to perturbations in the environment and task assumptions. This work considers approaches to these challenges in the context of a wet-lab robotic assistant. The tasks considered are cooperative transport with limited communication, and robot-assisted rapid experiment preparation requiring pouring from open containers useful for research and development scientist. For cooperative transport, robots must be able to plan collision-free trajectories and agree on a final destination to minimize internal forces on the carried load. Robot teammates are considered, where robots must reach consensus to minimize internal forces. Human leader, robot follower is then considered where robots must use non-verbal information to estimate the human leaders intended pose for the carried load. For experiment preparation, the robot must pour precisely from open containers in a single attempt. Two scenarios examined are when both pourer and receiver geometries and behaviors are known, and when the pourer must be approximated. An analytical solution is presented for a given geometry in the first instance. In the second instance, a combination of online system identification and leveraging of model priors are used to achieve the precision-pour in a single attempt with considerations for long-term robot deployment. The main contributions of this work are considerations for making robots capable of performing complex tasks with an emphasis on methods to combine classical and modern approaches for best performance.

February 19

NO SEMINAR

February 26

Pedro Saenz, Instructor in Applied Mathematics, Massachusetts Institute of Technology

"Interfacial Soft Matter"

Abstract:

Surface tension plays a critical role in a wide range of biological, environmental, technological and geophysical settings. In this talk, I will present three different problems dealing with interfacial soft matter that find motivation in markedly diverse areas. First, I will discuss the evaporation kinetics and flow dynamics of non-spherical sessile drops undergoing phase change. While previous investigations have been restricted to axisymetric drops, I will illustrate a number of new geometry-induced effects emerging from consideration of a range of non-spherical drops. Second, I will describe the non-equilibrium dynamics and statistical behavior of a hydrodynamic pilot-wave system, a liquid drop self-propelling on the surface of a vibrating fluid bath through a resonant interaction with its own wave field. In particular, I will consider the wave-mediated interaction of this active system with variable bottom topography to illustrate the emergence of wavelike statistics around defects, and spontaneous collective order and phase transitions in spin lattices. The final part of this talk will deal with active colloids. Specifically, I will consider the realignment of a Janus drop, a double-emulsion drop formed by two immiscible fluids, in response to an externally-imposed temperature gradient. The development of dynamically reconfigurable microlenses based on this mechanism will also be discussed.

Biography:

Pedro has been an Instructor in Applied Mathematics at MIT since August 2015. Before, he received his B.Sc. in Mechanical Engineering and M.Sc. in Civil Engineering from the University of La Rioja, Spain. He was awarded his Ph.D. in Fluid Mechanics from the University of Edinburgh, Scotland, and pursued brief postdoctoral research at the University of Maryland and Imperial College London from 2014 to 2015. His research blends experiments, numerical simulations, and theory, and seeks motivation in a variety of areas, ranging from engineering and biology to optics and quantum mechanics.

March 5

SPRING BREAK

March 12

NO SEMINAR

March 19

John C. Bischof, Carl and Janet Kuhrmeyer Chair, and Distinguished McKnight University Professor, Department of Mechanical Engineering, University of Minnesota

"Nanoparticle Heating for Therapeutics, Regenerative Medicine and Diagnostics"

Abstract:

Gold and iron oxide nanoparticles have unique and tunable properties that allow transduction of optical (light), or radiofrequency (RF) electromagnetic fields to affect heating of biomaterials at multiple scales. This talk will explore the underlying physics and relative advantages of each form of nanoparticle heating for therapeutic treatment of cancer or other disease by heating (i.e. magnetic hypothermia or photothermal cancer therapy). In addition, this same heating helps improve regenerative medicine by "nanowarming" vitrified (i.e. cryopreserved) biomaterials back to a transplantable state through rapid and uniform warming that avoids crystallization and cracking. This nanoparticle warming addresses an important technology bottleneck for both large systems (i.e. tissues and organs) and smaller systems (i.e. embryos and oocytes). In summary, this talk demonstrates the growing opportunites for nanoparticle heating in biomedical applications.

Biography:

Bischof works in the area of thermal bioengineering with a focus on biopreservation, thermal therapy, and nanomedicine. His awards include the ASME Van Mow Medal and Fellowships in societies including Cryobiology, JSPS, ASME and AIMBE. He has served as the President of the Society for Cryobiology and Chair of the Bioengineering Division of the ASME. Bischof obtained a B.S. in Bioengineering from U.C. Berkeley (UCB) in 1987, an M.S. from UCB and U.C. San Francisco in 1989 and Ph.D. in Mechanical Engineering from UCB in 1992. After a Post-doctoral fellowship at Harvard in the Center for Engineering in Medicine he joined the University of Minnesota in 1993. Bischof is now a Distinguished McKnight University Professor and Kuhrmeyer Chair in the Departments of Mechanical and Biomedical Engineering, and the Medtronic-Bakken Endowed Chair and Director of the Institute for Engineering in Medicine at the University of Minnesota.

March 26

Jacob Notbohm, Assistant Professor, Department of Engineering Physics, University of Wisconsin at Madison

"Force, Shape, and Motion in Collective Cell Migration"

Abstract:

Cells migrate collectively to form tissues, to heal wounds, and, in cancer, to metastasize. During these biological processes, the collective migration exhibits a transition from a solid-like state, wherein cell positions remain fixed, to a fluid-like state, wherein cells flow freely and rearrange their positions with their neighbors. Recent mechanics-based models and experiments have demonstrated that this transition can be predicted by average cell shape, with cells having more elongated shapes and greater perimeters more easily sliding past their neighbors. At each cell-cell interface, it has been proposed that active actomyosin contraction generated within the cell cortex acts as an effective surface tension tending to reduce each cell’s perimeter. Cell-cell adhesions have the opposite effect, tending to reduce the surface tension, thereby increasing the perimeter. It is unclear how cells regulate these competing factors in a confluent monolayer. This presentation will describe our investigation of the factors affecting cell surface tension and cell perimeter, and the corresponding effects on collective migration. Our experiments use monolayers of Madin-Darby Canine Kidney cells and quantify cell forces, shapes, and motion. With this experimental data, we test the theoretical predictions relating cell shape and motion.

Biography:

Jacob Notbohm is an Assistant Professor in the Department of Engineering Physics of the University of Wisconsin at Madison. He is also an Affiliate faculty of the Department of Mechanical Engineering and the Department of Biomedical Engineering, as well as a member of both the Carbone Cancer Institute and the McPherson Eye Research Institute. He obtained a B.S. in Engineering Mechanics at Wisconsin-Madison and a M.S. and Ph.D. in Mechanical Engineering at the California Institute of Technology.

Professor Notbohm’s lab studies how biological cells adhere, push, pull, and move. This work draws from a number of fields including engineering mechanics, soft matter physics, applied mathematics, and cell biology. He focuses primarily on the mechanical mechanisms underlying the cell and material behavior. Understanding these basic mechanisms will lead to new disease treatments and new approaches in tissue engineering.

April 2

Christopher M. Spadaccini, Director, Center for Engineered Materials and Manufacturing, Engineering Directorate, Lawrence Livermore National Laboratory

"Additive Manufacturing and Architected Materials"

Abstract:

Material properties are governed by the chemical composition and spatial arrangement of constituent elements. Over the past decade, the field of architected materials has sought to design, fabricate, and demonstrate materials with performance that is fundamentally controlled by geometry at multiple length-scales rather than chemical composition alone. There have been many advancements ranging from the maturation of additive manufacturing technologies which can be used to realize these materials, to inverse design methods such as topology optimization, and even includes unique new material feedstocks which make up the structures. This presentation will touch on all aspects of the architected materials realization process as well as evaluate performance of some of those materials. Specifically, we have demonstrated designer properties of these architected materials in polymers, metals, ceramics and combinations thereof. In addition to novel properties such as ultra-stiff lightweight materials, negative stiffness, and negative thermal expansion, I will present multifunctional architected materials with energy storage capability and architectures that respond to external fields. Many of these architected materials derived from advanced design and optimization methods which we have been developing and were fabricated with custom additive manufacturing techniques. These include projection microstereolithography (PµSL), direct ink writing (DIW), electrophoretic deposition (EPD), volumetric additive manufacturing (VAM), computed axial lithography (CAL), and diode-based additive manufacturing (DiAM) to name a few. New materials including graphene aerogel, carbon fiber composites, and printed glass will also be touched upon.

Biography:

Christopher M. Spadaccini, Ph.D., is currently the Director of the Additive Manufacturing Initiative at the Lawrence Livermore National Laboratory (LLNL) as well as the leader of the Center for Engineered Materials and Manufacturing. He has been working in advanced additive manufacturing process development and architected materials for the last decade and has over 50 journal publications, three book chapters, and 25 patents awarded and with 18 pending. Dr. Spadaccini founded several new fabrication laboratories at LLNL for process development focused on micro and nano-scale features and mixed material printing. He received his B.S., M.S., and Ph.D. degrees from the Department of Aeronautics and Astronautics at the Massachusetts Institute of Technology (MIT) in 1997, 1999, and 2004 respectively and has been a member of the LLNL technical staff for over 14 years. He has also been a lecturer in the Chemical, Materials, and Biomedical Engineering Department at the San Jose State University where he taught graduate courses in heat, mass, and momentum transfer.

April 8 (Monday): MEAM PhD Thesis Defense

John Cortes, Ph.D. Candidate, University of Pennsylvania
Advisor: Igor Bargatin

"Light-Driven Levitation of Ultralight Macroscopic Plates"

10:00 a.m., Room 319, Towne Building

Abstract:

The term “Micro-flyers” has generally been associated with centimeter-scale devices such as robotic insects or miniaturized drones. Due to manufacturing and aerodynamics challenges, propulsion at even smaller, sub-centimeter scales has historically been very difficult. In this work, we present a novel approach to micro-flyer devices at the sub-centimeter scale that combines photophoretic propulsion with ultralight plate metamaterials.

The photophoretic force is generated by a difference in temperature in a solid body or within the walls of a channel. We have used this unique phenomenon to develop micro-hovercrafts, which range from a few millimeters up to a centimeter in size and can hover hundreds of microns above an engineered low-stiction substrate at atmospheric pressure conditions. Under these conditions, a thin carbon nanotube layer absorbs incident light and heats up, resulting in the thermal transpiration flow from the cold end to the hot end of channels that are patterned through an ultralight plate. This flow then creates an overpressure underneath the plate, which causes it to lift-off and maintain a hovering gap between 300 µm and 600 µm for extended periods of time. The ultralight plates consist of a microfabricated plate metamaterial called nanocardboard, which is made from two face sheets interconnected by channels and features wall thicknesses in the 35-100 nm range, giving them areal densities as low as 0.5 g/m2.

This work also highlights the plate’s capabilities to fly at heights above 10 mm above a fine metal mesh at reduced pressures (as low as 10 Pa inside of a small vacuum chamber), which shows the potential of mid-air levitation without the dependence on a solid substrate. Not only can the plates fly at reduced pressures, but they also display the ability to liftoff and move a payload. We have developed theoretical models which are able to predict both the low-height hovering behavior as well as the reduced pressure capabilities of our ultralight plates. We show that our plates are excellent candidates for a novel approach to conducting atmospheric research in the Earth’s mesosphere as well as the Martian surface (given their ranges of ambient pressure).

April 9

James K. Guest, Associate Professor, Department of Civil Engineering, Johns Hopkins University

"Integrating Manufacturing and Topology Optimization for the Design of Architected Materials and Components"

Abstract:

Topology optimization has long been touted as a powerful tool capable of discovering innovative solutions to engineering design problems. It has been used to design 'structures' characterized at a range of length scales, from tens of microns (material architectures) to decameters (structures), for performance properties governed by a range of physics. Despite its tremendous potential as a design tool, topology optimized solutions are typically suboptimal when considering real-world operating conditions, design objectives, and manufacturing processes, and thus may require significant post-processing and re-design which is both detrimental and time consuming. This talk will review the topology optimization methodology and discuss our efforts at overcoming these shortcomings, with a particular emphasis on providing the design engineer geometric control to enable design for manufacturability. Several design examples will be presented including architected materials, components and devices that are fabricated through additive manufacturing, machining or 3D weaving, and optimized for mechanical, fluidic, and/or thermal properties.

Biography:

Jamie Guest is an Associate Professor at Johns Hopkins University in the Department of Civil Engineering, with a secondary appointment in Materials Science and Engineering. He is Deputy Director of the Johns Hopkins Center for Additive Manufacturing and Architected Materials, and leads the Topology Optimization Group at JHU. Jamie received his PhD in Civil Engineering from Princeton University and BSE in Civil Engineering Systems from the University of Pennsylvania. He currently serves as Secretary-General of the International Society for Structural and Multidisciplinary Optimization (ISSMO), as Chair of the ASCE Technical Committee on Optimal Structural Design, and on the Editorial Board for multiple journals. He received the 2015 Engineering Mechanics Institute (EMI) Leonardo da Vinci Award and the Walter L. Huber Research Prize in 2017, both from the ASCE.

April 16

Jorn Dunkel, Associate Professor of Physical Applied Mathematics, Department of Mathematics, Massachusetts Institute of Technology

"Wrinkles, Spaghetti & Knots"

Abstract:

Buckling, twisting and fracture are ubiquitous phenomena that, despite having been studied for centuries, still pose many interesting conceptual and practical challenges. In this talk, I will summarize recent theoretical and experimental work that aims to understand the role of curvature and torsion in wrinkle pattern selection, fragmentation cascades and knots. First, we will show how changes in curvature can induce phase transitions and topological defects in the wrinkling patterns on curved elastic surfaces. Thereafter, we will revisit an observation by Feynman who noted that dry spaghetti appears to fragment into at least three (but hardly ever two) pieces when placed under large bending stresses. Using a combination of experiments, simulations and analytical scaling arguments, we will demonstrate how twist can be used to control binary fracture of brittle elastic rods. Finally, in the last part, we will try to shed some light on how topology and torsion affect the stability of knots.

Biography:

Jörn Dunkel is Associate Professor of Physical Applied Mathematics at MIT. He joined the MIT mathematics faculty in 2013 as an Assistant Professor. Jörn received Diplomas in Physics (2004) and Mathematics (2005) from the Humboldt University Berlin, and completed his PhD at the University of Augsburg (2008). After two years of postdoctoral research at the Rudolf-Peierls Centre for Theoretical Physics in the University of Oxford, he spent three years as a Research Associate at DAMTP in the University of Cambridge. Working at the intersection of statistical and biological physics, Jörn's current research focuses on how physical properties of individual cells or microorganisms determine self organization, development and biological function in multicellular complexes. To this end, his group is developing and investigating mathematical models that describe dynamical behavior and structure formation in microbial and soft matter systems. Jörn was elected to a Junior Research Fellowship in Physics at Mansfield College, University of Oxford in 2008, and was named Research Fellow at Murray Edwards College, University of Cambridge in 2011. He is the recipient of the 2011 Gustav Hertz Prize of the German Physical Society. In 2015 Jörn was awarded an Alfred P Sloan Research Fellowship and an Edmund F. Kelly Research Award. He received a Complex Systems Scholar Award from the James S. McDonnell Foundation in 2016.

April 17 (Wednesday): MEAM/MSE Special Seminar

Harish Bhaskaran, Professor of Applied Nanomaterials at the University of Oxford, UK. Co-founder of Bodle Technologies

"Scalable Functional Phase Change Materials for Displays and Photonic Non-von Neumann Computing"

11:00 a.m., LRSM Reading Room

Abstract:

In electronics, doping silicon results in one of the most versatile functional materials ever employed. The pursuit of such functional materials in the optical domain is an area of great interest in the photonics community. I hope to convince you that whatever route photonics takes, a class of materials known as phase change materials, will play a key role in its commercialization. These materials can be addressed electrically, and whilst this can be used to control optical signals on photonic circuits this can also be used to create displays and smart windows. In this talk, I hope to give an overview of these applications of these materials with a view towards their near-term applications in displays, and their longer-term potential in integrated photonic memories to photonic machine-learning hardware components, with a few of our recent results in this area.

Biography:

Harish Bhaskaran is Professor of Applied Nanomaterials at the University of Oxford, UK and an entrepreneur having co-founded Bodle Technologies. He enjoys working on challenging technologies that have a shot at disruptive commercialization. This often involves a combination of device design and new functional materials at the nanoscale. A significant area of his research is also in new areas of additive nanomanufacturing to enable such devices to be made sustainably in the future. He holds a MS and PhD in Mechanical Engineering from the University of Maryland, College Park and a BE in Civil Engineering from the College of Engineering, Pune, and was a postdoc at IBM Zürich Research Laboratories.

 

April 23

J. Nathan Kutz, Robert Bolles and Yasuko Endo Professor of Applied Mathematics, University of Washington

"Data-driven Discovery of Governing Physical Laws in Engineering, Physics and Biology"

Abstract:

A major challenge in the study of dynamical systems is that of model discovery: turning data into models that are not just predictive, but provide insight into the nature of the underlying dynamical system that generated the da- ta. This problem is made more difficult by the fact that many systems of interest exhibit parametric dependencies and diverse behaviors across multiple time scales. We introduce a number of data-driven strategies for discover- ing nonlinear multiscale dynamical systems and their embeddings from data. We consider two canonical cases: (i) systems for which we have full measurements of the governing variables, and (ii) systems for which we have in- complete measurements. For systems with full state measurements, we show that the recent sparse identification of nonlinear dynamical systems (SINDy) method can discover governing equations with relatively little data and introduce a sampling method that allows SINDy to scale efficiently to problems with multiple time scales and parametric dependencies. Specifically, we can discover distinct governing equations at slow and fast scales. For systems with incomplete observations, we show that the Hankel alternative view of Koopman (HAVOK) method, based on time-delay embedding coordinates, can be used to obtain a linear model and Koopman invariant measurement system that nearly perfectly captures the dynamics of nonlinear quasiperiodic systems. We intro- duce two strategies for using HAVOK on systems with multiple time scales. Together, our approaches provide a suite of mathematical strategies for reducing the data required to discover and model nonlinear multiscale systems.

Biography:

Nathan Kutz is the Yasuko Endo and Robert Bolles Professor of Applied Mathematics at the University of Washington, having served as chair of the department from 2007-2015. He has a wide range of interests, including neuroscience to fluid dynamics where he integrates machine learning with dynamical systems and control.

April 30

Farhan Gandhi, Rosalind and John J. Redfern Jr Chair in Engineering, Department of Mechanical Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute

"Fault-Tolerant Control on VTOL Aircraft"

Abstract:

High-speed rotorcraft such as coaxial compound helicopters have a significant degree of control redundancy that can be exploited to minimize power requirement, noise, and vibration, in various flight conditions. This lecture focuses on a new idea – how control redundancy can be leveraged to compensate for control actuation failure. Both adaptive as well as robust strategies are examined, and operation post-failure is demonstrated via simulation. Multi-copters with greater than four rotors (hexacopters, octocopters, etc.), also offer control redundancy, allowing for safe operation post-failure by using the remaining (uncompromised) rotors. The lecture will examine the kind of failures that can be compensated on classical hexacopters and octocopters, along with the changes in rotor operational speed requirements, and the associated physics, post-failure.

Biography:

Farhan Gandhi is the Rosalind and John J. Redfern Jr. ’33 Endowed Chair in Aerospace Engineering at Rensselaer Polytechnic Institute (RPI) in the US. He is also RPI’s Aerospace Program Director, and Director of RPI’s Center for Mobility with Vertical Lift (MOVE). His research interest and activities cover the areas of rotorcraft aeromechanics, advanced rotary-wing configurations, multi-rotor aircraft, as well as smart/adaptive structures. Dr. Gandhi has been a visionary on reconfiguration in vertical lift platforms and high-speed rotorcraft and is credited with some of the most significant pioneering work in these areas with support from federal and state agencies as well as industry. He is a Technical Fellow of the American Helicopter Society, winner of the 1998 AHS Francios Xavier Bagnoud Award and the 2007 Popular Mechanics Breakthrough Award (for morphing rotors). He is a past Chair of the AHS Dynamics and Aircraft Design Technical Committees, and the AHS Education Committee. His research group at RPI comprises of eleven PhD students, two post-doctoral research scholars, and a number of undergrad and MS students. Dr. Gandhi is author of over 275 articles appearing in archival journals and technical conference proceedings.