“3D-Printed Shape-changing RV-PA Conduits for Pediatrics”
Presented by Dr. Galip Ozan Erol
Department of Mechanical Engineering, Johns Hopkins University
Each year, millions of infants are born in the US and it is estimated that 20% of the newborn deaths are due to the birth defects with congenital heart defects (CHDs) being the most common type (about 40,00 births every year). Right ventricle-to-Pulmonary artery (RV-PA) conduits are frequently used to treat these complex defects in pediatrics from birth. Currently used implants to treat these defects cannot adapt to the growth of the infants and they eventually require multiple (at least 3) open-heart replacement surgeries. Hence, these inevitable surgeries result in decrease in quality-of-life and increased medical burden as the infant grows and reaches adulthood. To address this issue, we have developed self-adaptable RV-PA conduits that can change their shape in response to the physiological changes such that fewer surgeries are required to maintain healthy pulmonary circulation during growth. In this talk, I will discuss our current progress on the development of 3D-printed self-adaptable RV-PA conduit designs and their numerical simulations under various mechanical loads mimicking infant growth. I will also present our experimental efforts to 3D print FDA-approved materials for cardiovascular devices and in-vitro functionality tests to demonstrate that the implants can undergo shape-change under pulsatile flow changes observed during growth. We believe that our self-adaptive conduits can contribute to minimizing the number of surgical operations during the growth of infants with CHDs.
Dr. Galip Ozan Erol is a postdoctoral fellow in the Department of Mechanical Engineering, and Chemical and Biomolecular Engineering, focusing on pediatric cardiovascular implants under the guidance of Profs. Sung-Hoon Kang, David Gracias, Lewis Romer and Narutoshi Hibino. Ozan graduated from the Middle East Technical University in 2009 with his Bachelor of Science Degree in Mechanical Engineering with a Minor in Mechatronics. He completed his Master’s Degree at Washington State University in 2010 with a focus on smart materials and actuators. In 2016, he received his PhD Degree from the University of Delaware (UD) where his research focused on the development of a multi-length scale design framework for advanced woven fabrics. During his PhD, he authored 9 journal publications in various journals, and received University of Delaware Dissertation Fellowship and Graduate Student Achievement awards. He is also a professional member of ASME and SAMPE.
“Light-based tools for investigating mechanisms and prevention of alcohol-induced congenital heart defects”
Presented by Professor Andrew Rollins
Biomedical Engineering and Medicine, Case Western Reserve University
Fetal alcohol syndrome (FAS) results from alcohol exposure during pregnancy and commonly includes growth retardation, craniofacial defects, and neurological abnormalities. Additionally, as high as 54% of live-born children with FAS have been shown to have congenital heart defects (CHD). Much remains unclear regarding the mechanisms of FAS-associated cardiac defects, especially on the influential role of altered early cardiac function (hemodynamics, conduction, biomechanical forces, etc.). This is largely due to a lack of imaging tools suitable for measuring this complex, miniscule, active organ. We have employed optical imaging tools based on optical coherence tomography (OCT) and optical conduction mapping to address these limitations. A quail model of FAS mimics a binge-drinking episode at gastrulation (week 3 in humans), when the embryo is highly vulnerable to the induction of CHDs. Two developmental stages were investigated: when the hearts were fully septated with four-chambers, and earlier, at looping stages when many important morphological changes happen. In rescue experiments, methyl donor compounds were introduced simultaneously with ethanol. Our results suggest that early functional abnormalities may serve as a mechanism for FAS-induced CHDs. Preliminary data show that Betaine and other methyl donors have the potential to rescue FAS-induced CHDs.
Dr. Rollins is a Professor of Biomedical Engineering at Case Western Reserve University, where he serves as Associate Chair for Undergraduate Education. His research interests are in the development and application of advanced biomedical optical technologies, especially optical coherence tomography (OCT), and including optical stimulation and imaging of electrophysiology. Current projects apply these technologies to the study of developmental cardiology, endoscopic imaging of cardiovascular disease, and measuring mechanical properties of the cornea.
“ENABLING ENGINEERED PROPERTIES VIA ARCHITECTURED MATERIALS”
Presented by Professor Jonathan Hopkins, University of California, Los Angeles
Architectured materials (a.k.a. mechanical metamaterials) achieve properties that derive primarily from their microstructure instead of their composition. Preliminary experimental and simulated results obtained from sub-millimeter-sized architectured-material samples show promise for achieving currently unobtainable combinations of super properties that will enable a host of next-generation technologies. The two most significant barriers preventing the practical implementation of such materials, however, include the following:
Professor Hopkins’ Flexible Research Group has focused much of their efforts at UCLA toward overcoming these challenges. This seminar will provide an overview of the design and fabrication tools generated by the Flexible Research Group in the context of practical architectured-material applications. The group’s design tools leverage the simplified mathematics of the Freedom and Constraint Topologies (FACT) synthesis approach to rapidly search the full design space of both periodic and nonperiodic architectured topologies to achieve desired combinations of properties. The group’s fabrication tools utilize custom-developed components (e.g., a flexure-based micro-mirror array) to generate multiple optical traps that are independently controlled to assemble large numbers of different material micro-particles simultaneously for rapidly constructing desired microstructures.
Jonathan Hopkins is an assistant professor at the University of California, Los Angeles and is the director of the Flexible Research Group. The aim of his group is to enable the creation of flexible structures, mechanisms, and materials that achieve extraordinary capabilities via the deformation of their constituent compliant elements. Prior to coming to UCLA, Jonathan was a postdoc at Lawrence Livermore National Laboratory from 2010 to 2013 and received his Ph.D. (2010), Masters (2007), and Bachelors (2005) degrees all in mechanical engineering at the Massachusetts Institute of Technology. He was honored by President Barack Obama at the White House with a DOE nominated PECASE award for his work involving the design and fabrication of architectured materials. Additionally, he is a recipient of ASME’s 2016 Freudenstein/General Motors Young Investigator Award, the V.M. Watanabe Excellence in Research Award, and the Northrop Grumman Excellence in Teaching Award.
4:10 pm Presentation
“Making the Case for (slightly) Non-Circular Pipes and Beams”
Presented by KARTHIK MENON (Adviser: Prof. Mittal)
The vortex-induced vibration response of a canonical bodies, such as a circular cylinder, has been the focus of a large number of studies. However, very little attention has been given to the effect of shape itself on the dynamics of these bodies. This study attempts to answer some fundamental questions about how the shape of a body changes its response. We show how very small changes in shape often lead to dramatic changes in the vibration response. Further, we attempt to understand this behaviour in terms of the fluid dynamic forcing on the oscillating body by employing some simplified models of vortex induced vibration.
4:35 pm Presentation
“Measurement of Surface Deformation using Structured Light Methods”
Presented by SUBRHRA SHANKHA KOLEY (Adviser: Prof. Katz)
Structured light method is a non-contact 3D surface measuring technique based on active stereo. In this method an arrangement of dots or stripes of varying intensity/color is projected on an object which is recorded on a camera. The geometric shape of the object distorts the projected pattern; this distortion is used to find the 3D surface shape of the object. In this talk, I will briefly explain the working principle and discuss the table top experiment designed to calculate surface deformation. The calibration procedures which has been followed will be discussed. The objective of this experiment was to generate data-sets of known depth and compare it with the calculated depth which will help us to improve the processing technique used in the experiment.
“Tissue Origami: engineered tissue folding by mechanical compaction of the mesenchyme”
Presented by Professor Zev Gartner, Department of Pharmaceutical Chemistry, University of California, San Francisco
Many tissues fold into complex shapes during development. Controlling this process in vitro would represent an important advance for tissue engineering. We use embryonic tissue explants, computational modeling, and 3D cell-patterning techniques to show that mechanical compaction of the mesenchyme is sufficient to drive tissue folding along programmed trajectories. The process requires cell contractility, generates strains at tissue interfaces, and causes patterns of collagen alignment around and between cell condensates. Aligned collagen fibers support elevated tensions that promote the folding of interfaces along predictable paths. We demonstrate the robustness and versatility of this strategy for sculpting tissue interfaces by directing the morphogenesis of a variety of folded tissue forms from patterns of mesenchymal condensates. Our studies provide insight into the active mechanical properties of the embryonic mesenchyme and establish engineering strategies for more robustly directing tissue morphogenesis ex vivo.
4:10 pm Presentation
“Viscoelastic Turbulent Channel Flow Laden with Neutrally Buoyant Particles”
Presented by AMIR ESTEGHAMATIAN (Adviser: Prof. Zaki)
The addition of small amounts of polymer or particles to turbulent flows can appreciably change its dynamics. In many applications, both effects are relevant and act simultaneously. We present the first direct numerical simulations of particle-laden viscoelastic turbulence, in a channel. Viscoelastic effects are included using the FENE-P model and the particles are resolved using an extension of immersed-boundary methods to viscoelastic fluids. We first investigate single phase viscoelastic turbulence and the mechanism that leads to polymer drag reduction. We subsequently examine the influence of finite-size particles on the turbulent structures in a Newtonian fluid. We show that in dense suspensions, the effect of particles in a Newtonian turbulent flow is two-fold: (a) attenuation of turbulent fluctuations and the Reynolds stress (b) increase of apparent viscosity due to the particle-stress effect. Hence, the net turbulent drag reduction/enhancement is determined by the competition between these two effects. Finally, we present early results from simulations of a dense suspension of neutrally buoyant particles in viscoelastic channel flow.
4:35 pm Presentation
“An Immersed Boundary based Generalized Newtonian Flow Solver: Implementation and Benchmarking”
Presented by SHANTANU BAILOOR (Adviser: Prof. Mittal)
The Newtonian approximation for hemodynamic modeling was historically justified on the grounds that blood exhibits nearly constant viscosity at high shear-rates, such as those found in steady flow in large arteries. However, with recent efforts towards addressing increasingly complex hemodynamic problems, the nonlinear properties of blood, particularly its shear-thinning nature, cannot be neglected. The present work is a step towards simulating thrombus generation and aggregation around bio-prosthetic aortic valves. Such multi-scale problems involve macroscopic flow through blood vessels and microscopic seepage through porous blood clots and require accurate description of viscosity variation over a large range of shear-rates. To this end, the development and benchmarking of a three-dimensional solver for simulating inelastic, shear-thinning and shear-thickening fluids is described. Two popular generalized Newtonian models are implemented and several benchmark problems are simulated. The results are compared with analytic solutions or those available in literature.
Date: Wednesday, May 2, 2018
Time: 2:00pm – 3:30pm
Location : Mason Hall, Room 101
Hosted by Johns Hopkins Department of Mechanical Engineering & Johns Hopkins Design Build Fly Team
George Bibel, professor of mechanical engineering at the University of North Dakota, will discuss his latest book, “Plane Crash: The Forensics of Aviation Disasters,” a captivating look at some of the most dramatic plane crashes of the modern age, including Asiana Airlines 214, Air France 447, and Malaysia Airlines 370.
About the book:
Plane Crash, an unprecedented collaboration between mechanical engineering professor George Bibel and airline Captain Robert Hedges, shares the riveting stories of both high-profile and lesser-known airplane accidents. Drawing on accident reports, eyewitness accounts, and simple diagrams to explain what went wrong in the plane and in the cockpit, Hedges provides invaluable insight into aviation human factors, while Bibel analyzes mechanical failures. No prior scientific knowledge is needed to understand the principles and procedures this book describes, only an interest in the view from what Captain Hedges describes as “the best seat in the house.”
About the author:
George Bibel is a professor of mechanical engineering at the University of North Dakota. He is the author of Beyond the Black Box: The Forensics of Airplane Crashes and Train Wreck: The Forensics of Rail Disasters. His books have been adapted into training courses and invited lectures at leading aerospace institutions such as NASA, MIT, and Boeing. Professor Bibel received a Ph.D. from Case Western Reserve University (1987) and an MS from University of Michigan (1980).
“How vegetation alters waves and current, and the feedbacks to environmental system function”
Presented by Professor Heidi Nepf
Donald and Martha Harleman Professor of Civil and Environmental Engineering
Massachusetts Institute of Technology
Vegetation provides a wide range of ecosystem services valued at over 4 trillion dollars per year. Seagrasses, salt marshes, and mangroves, damp storm surge and waves, mitigate anthropogenic nutrient loads, and provide important habitat and blue carbon reservoirs. The conservation and restoration of these landscapes has become the center-point of nature-based solutions for coastal protection and carbon mitigation. This seminar will summarize basic concepts in vegetation hydrodynamics, focusing on flexible meadows of seagrass, for which the bending of plants in response to fluid motion (called reconfiguration) plays an important role in setting the drag. Scaling laws are developed to describe the damping of currents, turbulence and waves as a function of plant morphology, flexibility, and shoot density. The feedbacks from plant-flow interaction to sediment transport and carbon sequestration are also discussed.
Heidi Nepf is the Donald and Martha Harleman Professor of Civil and Environmental Engineering at the Massachusetts Institute of Technology (MIT). She received a doctorate from Stanford University (1992) and spent one year at the Woods Hole Oceanographic Institution before beginning her career at MIT in 1993. She is internationally known for her work on the impact of vegetation on currents, waves, and sediment transport in channels, wetlands, and coastal zones. In recognition of her work in this field, she was selected for a NSF Career Award, the Borland Lecture, the Chapman Lecture, the Harold Schoemaker Best Paper Award [IAHR], and a Distinguished Alumni Award from Bucknell University. Dr. Nepf served on the National Research Council panel that reviewed the Army Corps’ Louisiana Coastal Protection and Restoration (LACPR) Program.
Sponsored by the Department of Mechanical Engineering and the JHU Student Section and the Baltimore Section of the American Society of Mechanical Engineers.
4:10 pm Presentation
“Estimation of Disturbance Propagation Velocity in Transitional Shear Flow”
Presented by IGAL GLUZMAN (Adviser: Prof. Gayme)
A novel method is presented for determining the propagation velocity vector of disturbance sources in transitional fluid flow, using the Degenerate Unmixing Estimation Technique (DUET). The approach used considers the flow state, as measured in sensors, as a mixture of disturbance sources. The DUET Blind Source Separation (BSS) method is used to recover the disturbance sources and their unknown mixing processes. Then, the propagation velocity vector of each of the identified sources is determined using sensor readings from (at least) three different locations in the flow field. The viability of the method is demonstrated via numerical simulations involving 3D Tollmien-Schlichting (TS) waves and wave-packets (WPs), that are linearly mixed and measured in a Blasius Boundary Layer (BBL). Wind-tunnel experiments complement the numerical results, in which the flow over a flat plate is considered. In these experiments, hot-wires are used as sensors, and plasma actuators are used to generate disturbance sources.
4:35 pm Presentation
“State Estimation in Cylindrical Couette Flow”
Presented by MENGZE WANG (Adviser: Prof. Zaki)
The state of transitional and turbulent cylindrical-Couette flows is very sensitive to initial conditions and the flow startup process. For example, initial disturbances with different wavenumbers can lead to a variety of transitional flow structures, such as stationary, traveling, and wavy Taylor vortices. These structures persist in the turbulent state. As a result, in numerical simulations, it is difficult to prescribe the appropriate initial condition which achieves a target flow state and comparisons to experiments become challenging. This problem is tackled using adjoint-based variational state estimation. The approach combines simulations with wall measurements to obtain a better initial condition, which converges to the correct state after a few time steps. We first consider estimation of a superposition of saturated wavy vortices. The reconstructed initial condition contains all the dominant modes, and after a short time, the accuracy of the estimated energy spectra, distorted mean profile, and mode shapes are quite satisfactory. We subsequently investigate the more challenging turbulent case. Although the estimation error is small near the wall, the turbulent fluctuations are underestimated in the bulk region, which is likely due to a lack of sensitivity of wall measurements to perturbations in the bulk of the flow.
3D Human Brain models in Microfluidics for the Study of Neurological Disorders
Presented by Professor Hansang Cho
University of North Carolina at Charlotte
With hundreds of billions of neurons and thousands of trillions of synaptic connections between them, the human brain is the most complex system on earth. However, there are no well-developed human brain models to study the brain activities in either laboratory environments or in animal bodies. Here, I present micro-scaled 3D environments that reconstruct a 3D human brain in Alzheimer’s disease (AD) by recapitulating AD signature of elevated levels of amyloid-beta (A-beta), tau proteins, activation of microglia, immune cells resident in a central nervous system (CNS), and consequent neuronal damage. Also, I present a brain vessel model of a 3D blood-brain barrier (BBB) for study of neurovascular diseases. The tightness of our BBB was validated by observing localized membrane proteins of VE-cadherin and ZO-1 along cellular boundary and blocking transmigration of innate immune cells through our BBB. To better understand the roles of the BBB in various diseases and for screening CNS-targeting drugs, our BBB disruption was demonstrated under neuroinflammatory and hypoxic pathologies.
Professor Hansang Cho’s research focuses on organ-on-chips, nanomedicine for the study of neurosciences and cancer biology, innovative mechanical components evolving multiple physics, and portable platforms for healthcare diagnostics and environmental sustainability. He received his B.S. and M.S in Mechanical Engineering from Seoul Nat’l University, Ph.D. in Bioengineering from University of California at Berkeley, and a postdoctoral training at Harvard Medical School. He received Cure Alzheimer’s Fund award, CRI Duke Energy Special Initiatives Funding award, Lawrence scholar program fellowship from Lawrence Livermore National Laboratory, Fellowship supported by Intel Inc., Study Abroad Scholarship by the Korean National Institute for International Education.