Seminars

Additive Manufacturing of Bio-inspired Structures via Multi-scale, Multi-material, and Multi-functional 3D Printing

Yong Chen

Professor & Director of Epstein Institute

Epstein Department of Industrial and Systems Engineering
and
Department of Aerospace and Mechanical Engineering (courtesy)
USC
Los Angeles, CA

Many natural structures out-perform conventional synthetic counterparts due to the specially evolved multi-scale, multi-material, and multi-functional architectures. However, most current 3D printing systems are designed to fabricate parts using a single material on a single scale, mainly for structural purposes. Such complex yet beautiful designs existing in natural structures are far beyond the fabrication capability of current 3D printing systems. This talk will report some of our recent work on developing new multi-scale, multi-material, and multi-functional additive manufacturing processes to fabricate bio-inspired structures, including the lobster structure, the nacre shell structure, the Salvinia molesta leaf structure, the limpet tooth structure, etc. After a brief overview of current 3D printing technology, several additive manufacturing (AM) processes to fabricate complex reinforcement architectures and functional surfaces will be presented. Some novel designs and promising applications enabled by the 3D-printed structures will also be discussed. The talk will conclude with remarks and thoughts on future 3D printing developments and potential opportunities for mechanical engineers.

Yong Chen is a professor of Industrial and Systems Engineering and Aerospace and Mechanical Engineering and the Director of Daniel J. Epstein Institute at the University of Southern California (USC). His research focuses on additive manufacturing (3D printing) in micro- and meso-scales. He has published more than 150 publications in refereed journals and conferences and 12 issued and pending U.S. patents. He received fourteen Best/Outstanding Paper Awards in major design and manufacturing conferences. Other major awards he received include the NSF CAREER Award and USC’s Innovation Commercialization Awards. Dr. Chen is a Fellow of the American Society of Mechanical Engineers (ASME). He has served as conference/program chairs and keynote speakers in several international design and manufacturing conferences.

Wednesday, January 20, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

Let Droplets Drop the Temperature: Fluids-Based Thermal Management

Patricia Weisensee

Assistant Professor

Institute of Materials Science and Engineering
Department of Mechanical Engineering and Materials Science
Washington University in St. Louis
St. Louis, MO

The coupling of fluid dynamics and heat transfer dominates many environmental and industrial processes, including the natural water cycle (evaporation from lakes and oceans, condensation in clouds), electronics thermal management, power generation, and materials manufacturing and processing. In this talk I will highlight two such phenomena: Condensation and evaporation, and advanced thermal management solutions using room-temperature liquid metals. I will focus on droplets, which are omnipresent in our daily lives, and provide the ability to actively manipulate the flow of matter and heat.

The major focus of my lab lies on understanding phase change phenomena, with a special emphasis on vapor-liquid (condensation) and liquid-vapor (evaporation or boiling) heat transfer. In this talk, I will show that water condensation on so-called lubricant-infused surfaces (LIS) can have up to 10-fold increased water collection efficiency due to an extremely high droplet mobility compared to bare metal surfaces. Lubricant wetting ridges surrounding droplets introduce an attractive capillary force, leading to self-propelled and gravity-independent droplet motion, which efficiently clears the surface for frequent re-nucleation. On the other hand, wettability-patterning a surface and thus restricting the mobility of droplets can be advantageous during evaporation. I will show that the alteration of convection within the droplets and localized evaporation-enhancement at the contact lines can effectively increase the overall heat transfer rates. In the last part of this talk I will introduce an ongoing project in collaboration with NASA, where my research group is developing a passive and compact thermal heat switch. I will present some preliminary results and highlight the challenges associated with using gallium-based liquid metals.

Patricia Weisensee is an Assistant Professor of Mechanical Engineering and Materials Science at Washington University in St. Louis (WashU). She earned her PhD in Mechanical Engineering from University of Illinois at Urbana-Champaign in 2016. She received a Diplom-Ingenieur in Mechanical Engineering from TU Munich in 2013 and also holds a M.S. in Materials Sciences from University of Illinois at Urbana-Champaign (2011). For her Diplom thesis on condensing steam bubbles in sub-cooled flow, Dr. Weisensee received the Siemens Energy Award 2014. She is an alumna of the German National Academic Foundation (“Studienstiftung des deutschen Volkes”), Germany’s largest, oldest, and most prestigious scholarship foundation.

At WashU, Dr. Weisensee leads the Thermal Fluids Research Group, which focuses on understanding the interplay of fluid dynamics and heat transfer of droplets and other multi-phase systems. Practical applications of interest are phase change heat transfer for thermal management, thermal storage, and water harvesting, metallic additive manufacturing, and droplet interactions with natural systems. To fundamentally study these thermal-fluidic interactions, her group combines multiple experimental techniques, such as high-speed optical and infrared (IR) imaging, interferometry, confocal fluorescence microscopy, and conventional heat transfer measurements. Dr. Weisensee is a very recent recipient of the NSF CAREER award and currently also holds a 3-year NSF research award to study nucleation and condensation of water on lubricant-infused surfaces (LIS). She was awarded the ACS Petroleum Research Fund Doctoral New Investigator grant to study the pore-scale interactions between fluid flow and heat transfer for oil-water emulsion flow through porous media, and received the prestigious NASA Early Career Faculty Award to develop a passive and compact thermal heat switch to be used on satellites and robots during lunar missions. Recently, Dr. Weisensee also received the 2020 ASME ICNMM Outstanding Early Investigator Award and 2020 Emerson Excellence in Teaching award.

Wednesday, January 27, 2021
3:30 PM
This seminar was held as a webinar.

host: Sadhal

Saliva Particle Transport During Cough & Breathing: Insights on Effective Social Distancing & Face Mask Wearing Gained by LES

Ali Khosronejad

Assistant Professor of Civil Engineering
Civil Engineering Department
The State University of New York at Stony Brook
Stony Brook, NY

The Coronavirus disease outbreak of 2019 has been causing significant loss of life and unprecedented economical loss throughout the world. Social distancing and face masks are widely recommended around the globe in order to protect others and prevent the spread of the virus through breathing, coughing, and sneezing. To expand the scientific underpinnings of such recommendations, we carry out high-fidelity computational fluid dynamics simulations of unprecedented resolution and realism to elucidate the underlying physics of saliva particulate transport during human cough and normal breathing with and without facial masks. Our simulations: (a) are carried out under both a stagnant ambient flow (indoor) and a mild unidirectional breeze (outdoor); (b) incorporate the effect of human anatomy on the flow; (c) account for both medical and non-medical grade masks; and (d) consider a wide spectrum of particulate sizes, ranging from 0 µm (passive tracer) to 300 µm. We show that during indoor coughing some saliva particulates could travel up to 0.48 m, 0.73 m, and 2.62 m for the cases with medical-grade, non-medical grade, and without facial masks, respectively. Thus, in indoor environments either medical or non-medical grade facial masks can successfully limit the spreading of saliva particulates to others. Under outdoor conditions with a unidirectional mild breeze, however, leakage flow through the mask can cause saliva particulates to be entrained into the energetic shear layers around the body and transported very fast at large distances by the turbulent flow, thus, limiting the effectiveness of facial masks.

Ali Khosronejad earned his Ph.D. in Civil Engineering (Hydraulic Engineering) from Tarbiat Modarres University (Tehran) in 2006. He earned a BS in Water Resources Engineering from Tehran University and a MS in Civil Engineering (Hydraulic Engineering) from Sharif University of Technology (Tehran). During his Ph.D. work he was a Research Assistant at the University of Ottawa, Canada. After graduating he became an Assistant Professor at the University of Guilan (Rasht, Iran) before becoming a postdoc at the University of Minnesota's St. Anthony Falls Lab in Minneapolis. In 2016, he moved to Stony Brook as an Assistant Professor.

Ali's research interests center around high performance computing tools. He develops algorithms for fluid-structure interaction; immersed boundary methods; coupled sediment transport in turbulent flow; and large eddy simulations of turbulent atmospheric and aquatic flows, free-surface and bubbly flows, density current and stratified flows, turbulent flows over natural and engineered rough surfaces, and transport and mixing of particles and conservative/non-conservative contaminants in natural riverine and coastal areas.

Wednesday, February 3, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

Learning From the Past

Gen(ret) Ellen Pawlikowski

Judge Widney Professor of Systems Architecting and Systems Engineering

USC
Los Angeles, CA

Department of Defense acquisition programs are the means that new capabilities are developed, acquired and fielded to support military operations. These programs can span decades as they often include evolving complex systems of systems. New practitioners (program managers and engineers) tend to get overwhelmed and at the same time discover that the tools to apply such information to their current task are deficient or lacking. In today’s world of ever-growing complexity and increasingly compressed timelines, there is seldom enough time to gain the depth and breadth of experience needed. This recognition provides the impetus to leverage case studies as an “experience accelerator.” Case studies provide tools for acquisition practitioners to learn from the experience of those program managers and systems engineers that preceded them. This presentation provides a foundation for conducting and using case studies in systems engineering and management.

General (retired) Ellen M Pawlikowski is an independent consultant providing expertise on strategic planning, program management, logistics, and research and development. She is the Judge Widney Professor at the Viterbi School of Engineering at the University of Southern California. She serves on the Boards of Directors for the Raytheon Company, Intelsat SA, Applied Research Associates, and SRI International. Ellen Pawlikowski was the third woman to achieve the rank of General in the US Air Force. In her last assignment, she served as Commander, Air Force Materiel Command, Wright-Patterson Air Force Base, Ohio. The command employs some 80,000 people and manages $60 billion annually, providing the Air Force with research and development, life cycle systems management, test and evaluation, installation support, depot maintenance and supply chain management.

She entered the Air Force in 1978 as a distinguished graduate of the ROTC program at the New Jersey Institute of Technology, Newark, NJ. She then attended the University of California at Berkeley as a Fannie and John Hertz Foundation fellow and received a Doctorate in chemical engineering in December 1981.

General Pawlikowski's career has spanned a wide variety of technical management, leadership and staff positions. She commanded five times as a general officer, commanding the MILSATCOM Systems Wing, the AF element of the National Reconnaissance Office, AF Research Laboratory, the Space and Missile Systems Center, and Air force Materiel Command. She also served as the program director and program executive officer for several multibillion-dollar military-system acquisitions.

General Pawlikowski is nationally recognized for her leadership and technical management acumen. Among her recognitions are the Women In Aerospace Life Time Achievement Award, the NDIA’s Peter B Teets Award, and the Air Force Association Executive Management Award. She is a Honorary Fellow of the American Institute of Aeronautics and Astronautics, a Fellow of the Directed Energy Professional Society, and a member of the National Academy of Engineers.

Ellen Pawlikowski was born in Bloomfield, NJ and currently resides in Macon, GA.

Wednesday, February 10, 2021
3:30 PM
This seminar was held as a webinar.

host: Ronney

Simple Rules for the Wrinkle Patterns of Confined Elastic Shells

Ian Tobasco

Assistant Professor
Department of Mathematics, Statistics, and Computer Science
Univ. Illinois Chicago
Chicago, IL

Dried fruits wrinkle for the same reason that leaves and flowers do — mechanical instabilities arising from a mismatch in lengths. Can such geometric incompatibilities be used to design and control wrinkle patterns at will? This talk will discuss the possibility of designing wrinkle patterns "in the large" using a recently derived model for the wrinkles of confined elastic shells. After recalling the basic mechanics and introducing our model, we show how it can be solved by hand in many cases to predict the wrinkled topography. Solving this model produces a few geometric rules, which explain the layout of the wrinkle peaks and troughs across examples. These simple rules reproduce the patterns seen in numerous experiments and simulations, even ones that exhibit a surprising coexistence between orderly wrinkles and a more disordered response. Knowing such rules for wrinkles opens the way towards designer wrinkle patterns, with potential applications from flexible electronics to synthetic skins.

Ian Tobasco is an Assistant Professor at the University of Illinois at Chicago Department of Mathematics, Statistics, and Computer Science. He holds a Ph.D. in Mathematics from the Courant Institute of Mathematical Sciences at New York University, and a B.S.E. in Aerospace Engineering from the University of Michigan.

Ian’s research on the calculus of variations and partial differential equations concerns problems that sit at the interface of mathematics, physics, and engineering, where advances in pure mathematical analysis can lead to scientific breakthroughs in the lab and vice versa. Ian’s recent work involves the use of energy minimization to explain and classify the zoo of wrinkling, crumpling, and folding patterns exhibited by thin elastic sheets. Other interests include the design of optimal transport mechanisms in fluid dynamics and their comparison with naturally occurring turbulent transport, as well as the variational analysis of spin glasses.

Wednesday, February 17, 2021
3:30 PM
This seminar was held as a webinar.

host: Plucinsky

Mesoscale Modeling for Next Generation DNA Sequencing and Sustainable Energy

Giovanna Bucci

Senior Research Engineer
Energy Technologies Division
Bosch

There is great potential for genome sequencing to enhance patient care through improved diagnostic sensitivity and more precise therapeutic targeting. The opportunity to detect repetitive regions and structural variation in the genome has incentivized the development of long-read DNA sequencing. Nano-channel analysis is one of the emerging strategies for non-optical DNA sequencing. However, high cost, low throughput, and low accuracy have so far limited the adoption of long-read technologies. In this work, mesoscale modeling tools are employed to simulate the mechanics of DNA loading and reading, and predict the statistics of polymer-chain conformation under confinement. A workflow was developed to quantify competing requirements of efficiency and accuracy and extract metrics that guide design optimization. Several design variables (geometry, electric field, materials and interfaces, buffer solution, etc.) can be tuned to achieve high throughput base-pair detection. This multi-dimensional design space offers a great opportunity for modeling to provide understanding and accelerate innovation.

Finally, I will provide an overview of my recent work in energy storage/conversion technologies, with a brief discussion of a new theoretical and computational framework to study electrochemical instability and coarsening of catalyst nano-particles.

Giovanna Bucci is a Senior Research Engineer in the Energy Technologies Division at Bosch, where she has been responsible for the mesoscale modeling of aging in Li-ion batteries and in proton exchange membrane fuel cells. Currently, she leads a modeling effort to optimize the design of a DNA sequencing device based on nano-confinement.

Giovanna began her career in the field of computational solid mechanics, with an emphasis on fracture and large-scale simulation. She worked on next-generation energy storage devices, with postdocs at Brown University and in the Carter/Chiang research group at MIT DMSE. Her analyses have established design rules for silicon anodes, and identified failure-tolerant battery microstructures and operating conditions. In recognition of her cross-disciplinary accomplishments, she received the 2015 Rising Stars in Nuclear Science and Engineering award at MIT.

Giovanna took her Ph.D. in Structural Mechanics from the Politecnico di Milano and her M.S. and B.S. in Architecture from Università di Pavia.

Wednesday, February 24, 2021
3:30 PM
This seminar was held as a webinar.

host: Balakrishna

Machine Learning for High-Throughput Experiment and Analysis of Processing-Property Relationships

Samantha Daly

Professor
Department of Mechanical Engineering
University of California at Santa Barbara
Santa Barbara, CA

Materials have hierarchical and heterogeneous structures that drive their deformation and failure mechanisms. The relationship between structure and behavior -- such as the impact of the microstructure of a polycrystalline metal on twinning, dislocation slip, grain boundary sliding, and multi-crack systems -- includes complex stochastic and deterministic factors whose interactions are under active debate. In this talk, the application of data-driven approaches to microscale displacement data for the high-throughput segmentation, identification, and analysis of twinning in magnesium (a deformation mechanism that is critical to its ductility and forming) will be discussed. This will include an analysis of deformation twinning over thousands of grains per test, including an analysis of the impact of microstructure on the relative activity of specific twin variants (automatically identified from microscale strain fields) and their evolution under load. The newly developed experimental and analytical approaches are length scale independent and material agnostic, and can be modified to identify a range of deformation and failure mechanisms.

Samantha (Sam) Daly is a Professor in the Department of Mechanical Engineering at the University of California at Santa Barbara. She received her Ph.D. from Caltech in 2007 and subsequently joined the University of Michigan, where she was on the faculty until 2016 prior to her move to UCSB. The Daly group investigates the mechanics of materials, with a focus on fatigue, fracture, creep, composites, multi-functional materials, and new experimental and data-driven approaches for the characterization of processing – structure – property relationships. Her recognitions include the Experimental Mechanics Best Paper of the Year Award, IJSS Best Paper of the Year Award, DOE Early Career Award, NSF CAREER Award, AFOSR-YIP Award, ASME Eshelby Mechanics Award, Journal of Strain Analysis Young Investigator Award, ASME Orr Award, and Caddell Award. She currently serves on the Executive Board of the Society of Experimental Mechanics, and as an Associate Editor of the journals Applied Mechanics Reviews, Experimental Mechanics, and Strain.

Wednesday, March 3, 2021
3:30 PM
This seminar was held as a webinar.

host: Balakrishna

Toward Predictive Yet Affordable Computations of Practical Wall-Bounded Turbulent Flows

George Park

Assistant Professor
Department of Mechanical Engineering and Applied Mechanics
School of Engineering and Applied Sciences
University of Pennsylvania
Philadelphia, PA

Kinetic energy of turbulence is generated at large scales controlled by boundary conditions, but it is dissipated into heat at the smallest scales. The ratio of these two length scales increases rapidly with Reynolds number. Solid walls add another dimension in this scale landscape, where the scale separation gets progressively less pronounced toward the wall. This has significant ramifications on the cost of scale-resolving simulation of practical engineering flows, such as those found in aircraft, wind turbines, and ship hydrodynamics. Direct approaches with full resolution of length and times scales close to the wall are still infeasible with current computing power. The demand for superior designs at reduced cost has led researchers to explore alternative computational approaches that have potential to be predictive yet affordable. Large-eddy simulation (LES) is one such approach where only the energy-containing scales are resolved directly, and the effect of the unresolved motions are modeled. In practical LES calculations, subgrid-scale (SGS) models are used in conjunction with wall models to augment the turbulent shear stress, which otherwise is underpredicted on coarse grids and leads to inaccurate prediction of mean and turbulence quantities.

In this talk, I will discuss the research in my group on this wall-modeled LES approach. Widely used wall-modeling techniques will be discussed with their applications to canonical and complex wall-bounded flows. Challenges in robust and efficient implementation of the models in flow solvers for handling practical geometries will be discussed. I will also highlight recent work to predict flow over realistic aircraft geometries at flight conditions and a boundary layer with mean three dimensionality.

George Park is an Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. He received his Ph.D. and M.S. in Mechanical Engineering (ME) from Stanford University in 2014 and 2011, respectively, and his B.S. in ME from Seoul National University, South Korea in 2009. He worked as a postdoctoral fellow and an engineering research associate at the Center for Turbulence Research (Stanford) prior to joining UPenn as a faculty member in 2018. His research interests include high-fidelity numerical simulation of complex wall-bounded turbulent flows, computational methods with unstructured grids, non-equilibrium turbulent boundary layers, and fluid-structure interaction.

Wednesday, March 10, 2021
3:30 PM
This seminar was held as a webinar.

host: Bermejo-Moreno

Vortex in the Eye: Thermal Effects on Fluid Mixing in the Eye

Morteza Gharib

Hans W. LiepmannProfessor of Aeronautics and Bioinspired Engineering; Booth-Kresa Leadership Chair, Center for Autonomous Systems and Technologies; Director, Graduate Aerospace Laboratories; Director, Center for Autonomous Systems and Technologies

Graduate Aerospace Laboratory and Medical Engineering Department
California Institute of Technology
Pasadena, CA

Age-related macular degeneration (AMD) is the leading cause of central vision loss in the developed world. Wet AMD can be managed through serial intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents. However, sometimes the treatment is ineffective. Given that the half-life of the drug is limited, inefficient mixing of the injected drug in the vitreous chamber of the eye may contribute to the ineffectiveness. Here, we introduce thermal heating as a means of enhancing the mixing-process in the vitreous chamber and investigate parameters that potentially influence its effectiveness. Our in-vitro studies point to the importance of the location of the heating on the eye. A significant increase in the mixing and delivery of drugs to the targeted area (the macula) could be achieved by placing heating pads so that a current against gravity is induced in the vitreous. The presented results can potentially help in the development of a better strategy for intravitreal injection and improve the quality of patient care.

Mory Gharib is Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering; Chair of Graduate Aerospace Department (GALCIT); Director of Center for Autonomous Systems and Technologies. He received his B.S. degree in Mechanical Engineering from Tehran University (1975) and his M.S. 1978, in Aerospace and Mechanical Engineering from Syracuse University and his Ph.D.1983, in Aeronautics from Caltech. He joined Caltech as a professor of Aeronautics.

Professor Gharib's current research interests in conventional fluid dynamics and aeronautics include Vortex dynamics, active and passive flow control, autonomous flight, and underwater systems. His Biological flows research includes cardiovascular and ophthalmology, and medical devices.

Dr. Gharib's honors and affiliations include: Member, American Academy of Arts and Sciences; Member, National Academy of Engineering; Charter Fellow, National Academy of Inventors; Fellow, American Association for the Advancement of Science; Fellow, American Physical Society; Fellow, American Society of Mechanical EngineeringHe has received the G.I. Taylor Medal from the Society of Engineering Sciences, The Fluid Dynamics Prize from the American Physical Society and five new technology recognition awards from NASA in the fields of advanced laser imaging and nanotechnology. In 2008 he received R&D Magazine's "R&D 100 innovation award" for one of the year's best inventions for his 3-D imaging camera system. Additionally, Dr. Gharib has published more than 250 papers in refereed journals and has been issued 120 U.S. Patents.

Wednesday, March 17, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

The Fluid Mechanics of Hypersonic Fluid-Structure Interactions

Daniel Bodony

Blue Waters Professor
Department of Aerospace Engineering
Univ. Illinois Urbana-Champaign

The interaction of high-speed aerodynamics with thermo-mechanically compliant structures is a critical design consideration for single-use and reusable hypersonic vehicles. Historical techniques for predicting fluid-thermal-structure interaction (FTSI) are insufficient for envisioned hypersonic flight systems, leading to a resurgent effort towards understanding, modeling, and predicting FTSI-coupled systems. In this talk, we will present the impact of FTSI on two fundamental scenarios -- boundary layer transition and shock-boundary layer interaction -- informed using a combination of stability analyses and direct numerical simulation techniques. In each scenario, focus will be given to the fluid mechanics involved in the fluid-structure coupling. Supporting details on the relevant theoretical and numerical details required for accurate prediction will also be discussed.

Daniel J. Bodony is the Blue Waters Professor, Donald Biggar Willett Faculty Scholar and Associate Head for Graduate Programs in the Department of Aerospace Engineering at the University of Illinois. He received his Ph.D. in Aeronautics & Astronautics from Stanford University in 2005. After working at the NASA Ames/Stanford Center for Turbulence Research he joined the University of Illinois in late 2006 as an assistant professor. He received an NSF CAREER award in 2012 in Fluid Dynamics, is an Associate Fellow of the AIAA, and received the University of Illinois' Promotion with Distinction Award in 2020

Wednesday, March 24, 2021
3:30 PM
The Zoom webinar is at https://usc.zoom.us/j/91084441303.

host: Bermejo-Moreno

Hypervelocity Spherically-Blunted Cone Flows in Mars Entry Ground Testing

Joanna Austin

Professor of Aerospace
Graduate Aerospace Laboratories
Caltech
Pasadena, CA

The intent to launch larger vehicles in future Mars missions increases the requirements for ground testing in the high-stagnation enthalpy environment encountered by the vehicle during the hypersonic phase of entry, descent and landing. During atmospheric entry, strong shock compression and high post-shock temperatures lead to significant chemical dissociation and vibrational excitation in the shock layer in front of a sphere-cone capsule, particularly near the stagnation region. For Mars missions, accurate thermochemical modeling of carbon dioxide, a principal component of the atmosphere with complex vibrational energy exchange, is particularly important. We examine the shock layer over sphere and spherically-blunted cone geometries through reacting Navier-Stokes simulations and experiments in two facilities capable of high-stagnation enthalpy, hypersonic flows simulating Mars planetary entry conditions: the T5 Reflected Shock Tunnel and the Hypervelocity Expansion Tube. A recently-developed unified model for sphere and sphere-cone behavior is first verified for high-stagnation enthalpy CO2 flows through simulations with thermal and chemical nonequilibrium. Shock standoff distance measurements in both facilities are in good agreement with model predictions. The need to account for the divergence of the streamlines in conical nozzles is highlighted and an existing model is extended to account for changes in shock curvature between parallel and conical flow. The contributions of vibrational and chemical nonequilibrium to the stagnation line density profile are quantified using the simulation results comparing three chemical kinetic models. Experimental measurement of fore- and aftbody MWIR radiation will also be discussed.

Joanna Austin is Professor of Aerospace at the Graduate Aerospace Laboratories, California Institute of Technology. She received B.E. (Mechanical and Space Engineering) and B.Sc. (Mathematics) degrees from the University of Queensland, Australia, and M.S. followed by Ph.D. (2003) degrees in Aeronautics from the California Institute of Technology. Austin then joined the faculty in the Aerospace Engineering department at the University of Illinois, becoming Associate Professor and Willett Faculty Scholar, before moving back to Caltech in 2014, where she is a co-PI in the Caltech Hypersonics Group. Austin's research is focused on fundamental problems in reactive, compressible flows across a broad range of applications including hypervelocity flight, supersonic combustion and detonation, bubble dynamics, and explosive geological events.

Wednesday, March 31, 2021
3:30 PM
This seminar was held as a webinar.

host: Bermejo-Moreno

A Nanoscale View on Electromechanical Phenomena

Nina Balke

Member of the Technical Staff
Center for Nanophase Materials Sciences
Oak Ridge National Laboratory
Oak Ridge, TN

The ability to transform electrical energy into mechanical energy and vice versa is the foundation to many technologies in the area of information and energy, such as sensors, piezotronics, energy harvesting, piezoelectric, electrochemical, and polymer actuators, and artificial muscles. Despite the importance of electromechanical phenomena and numerous applications, fundamental interdisciplinary studies needed to understand, and control electromechanical phenomena on the nanoscale are lacking. Atomic force microscopy (AFM) is well suited to measure local volume changes in the picometer range and has a lateral resolution of 10’s of nanometer which makes this an ideal technique to address electromechanical phenomena on the nanoscale. Despite the technical advances and the development of new SPM-based characterization techniques, the quantification of functional material parameters based on electromechanical phenomena is still elusive. The lack of quantitative and accurate measurement can also lead to the misinterpretation of relevant material physics. Only if quantitative material parameters can be extracted, can a correlation of nanoscale structure-function relationships be derived, and AFM can be integrated with techniques probing smaller or larger length and time scales as well as theoretical efforts for a full information integration across different disciplines. I will give an overview over which electromechanical phenomena can be probed quantitatively including electro-chemo-mechanical coupling to understand local electrochemical reactions and processes in electrochemical capacitors. Then I will talk in depth about AFM and ferroelectric materials and how the quantitative measurement of piezoelectric material properties led to the discovery of layered 2D van der Waals ferroelectrics with highly unusual material properties and functionalities based on the presence of four polar phases and high ion conductivity. These materials demonstrate, for the first time, how physical order parameter can be controlled by ionic degrees of freedom which will open new concepts for functional heterostructures and electronic devices.

Nina Balke received her Ph.D in Materials Sciences from the Technical University of Darmstadt, Germany, in 2006. After being a Feodor-Lynen fellow of the Alexander von Humboldt foundation at the University of California in Berkeley she became a research staff at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory in 2010. She is specialized in nanoscale characterization of electromechanical effects and electro-chemo-mechanical coupling using atomic force microscopy in oxides and vdW layered materials. Her scientific focus includes ferroelectrics, dielectrics, and energy storage materials as well as in-situ characterization of solid-liquid interfaces.

Wednesday, April 14, 2021
3:30 PM
The Zoom webinar is at https://usc.zoom.us/j/92982374143.

host: Balakrishna

Probing Phase Transformations and Twinning Across Length Scales Using 3D X-Ray Microscopy

Ashley N. Bucsek

Assistant Professor
Mechanical Engineering
University of Michigan
Ann Arbor, MI

Advanced materials are broadly defined as innovative materials that have atypical sizes, microstructures, and responses. These atypical characteristics enable major, previously impossible technological breakthroughs, yet many advanced materials owe their desirable properties to complex underlying micromechanics including twinning, detwinning, and martensitic phase transformations. Establishing the relationships between these local micromechanics and macroscopic material behavior is critical to accelerating the implementation of advanced materials. Toward these goals, we utilize modern 3D X-ray diffraction techniques that offer the capability to measure the deformation and microstructure evolution inside bulk materials, in situ, and across nine orders of magnitude in length scales (nm to mm). Measured quantities include the 3D microstructure “map” and spatially-resolved crystallographic orientation, elastic strain tensor, and phase fraction. These techniques can be used to simultaneously measure local microstructure events and the consequent macroscopic response, resulting in a tool uniquely suited for linking local micromechanics to material behavior. These capabilities will be illustrated using a number of research examples involving twinning and phase-transforming materials, using nickel-titanium shape memory alloys as a model material system. Ongoing and future work will also be discussed, including the development of a first-of-its kind laboratory-scale instrument to conduct 3D X-ray diffraction experiments in-house.

Ashley Bucsek is an assistant professor in Mechanical Engineering at the University of Michigan. Previously, she was a President's Postdoctoral Fellow at the University of Minnesota and a visiting scientist on beamline ID06 at the ESRF. She holds an MS and PhD from Colorado School of Mines and a BSE from the University of Wyoming. Bucsek's research combines 3D X-ray diffraction microscopy with micromechanical theory to study deformation and microstructure evolution in structural and functional materials. She is a regular user at the APS, CHESS, and the ESRF and is currently developing a laboratory-scale high energy diffraction microscopy microscope. Bucsek is also a board member on ASM’s International Organization on Shape Memory and Superelastic Technologies, an editorial advisory board member of the Shape Memory and Superelasticity journal, an APS Imaging/Microbeam proposal review panel member, and a member of the DOE-funded PRISMS Center.

Wednesday, April 21, 2021
3:30 PM
This seminar was held as a webinar.

host: Plucinsky

Wearable Opto-mechanical System for Cardiovascular Monitoring: From Methodological Design to Device Development

Jing Liu

Postdoctoral Scholar
Department of Aerospace and Mechanical Engineering
USC
Los Angeles, CA

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. There are about 47% of sudden cardiac deaths occurring outside a hospital, which reveals the demand for wearable medical devices that can monitor the cardiovascular risk factors of individuals frequently, accurately, and unobtrusively in their daily life. At the same time, the use of wearable medical devices allows healthcare givers to assess patient’s health conditions and provide medical guidance in a timely and non-contact way.

The photoplethysmography (PPG) sensor composed of light-emitting diode and photodetector has been widely adopted by various wearable fitness trackers owing to its low cost, compact size and ease of use. However, so far, the applications of PPG are mainly limited to heart rate and blood oxygen saturation measurement. By utilizing the wavelength dependence of the light penetration depth into the skin, we have developed a multi-wavelength PPG (MWPPG) sensing approach which allows for probing blood pulsations in different types of skin blood vessels.

In this talk, two MWPPG applications for cardiovascular monitoring will be presented: 1) cuffless arterial blood pressure measurement with a single MWPPG sensor; and 2) an opto-mechanical device equipped with an MWPPG sensor to enable arterial and capillary blood pressure measurement.

Jing Liu is a postdoctoral scholar in the Department of Aerospace and Mechanical Engineering, University of Southern California. She received her Ph.D. in Electronic Engineering from the Chinese University of Hong Kong in 2018 and her B.S. degree in Computer Science from Wuhan University in 2014. Her main achievements include the inventions of multi-wavelength photoplethysmography for wearable blood pressure monitoring, which is under commercialization in the Hong Kong Technology Start-up Support Scheme for Universities Programme. Her current research interests are cardiac modeling, physiological signal processing, and machine learning for cardiovascular health informatics.

Wednesday, April 28, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan