http://s.uconn.edu/meseminar4.15.22

Abstract: Two-phase internal flows in microgaps with passage hydraulic diameters of 100 um – 1,000 um are of interest in three-dimensional heterogeneous electronics, transport electrification, and portable microsystems.  To enhance heat transfer coefficients in these configurations, structured surfaces are often employed.  Understanding of two-phase flow and thermal transport in such configurations continues to be an active area of research.  This talk will present recent computational and experimental results from investigations of two-phase forced convection, capillary assisted transport, and capillary flow driven passive transport in structured microgaps.  Experimental results include the use of high speed visualizations to elucidate flow regimes, and temperature measurements for heat transfer characterization.  Computations of two-phase flows have been performed using the volume of fluid approach.  While many challenges remain, experimentally validated modeling of such two-phase flows presents a promising approach for understanding the thermal transport in these configurations, and employing them in thermal management in emerging applications.

Biographical Sketch: Yogendra Joshi is Professor and John M. McKenney and Warren D. Shiver Distinguished Chair at the G.W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology.  His research interests are in multi-scale thermal management.  He is the author or co-author of nearly four hundred and fifty publications in this area, including nearly two hundred journal articles. He received his B. Tech. in Mechanical Engineering from the Indian Institute of Technology (Kanpur) in 1979, M.S. in Mechanical Engineering from the State University of New York at Buffalo in 1981, and Ph.D. in Mechanical Engineering and Applied Mechanics, from the University of Pennsylvania in 1984.  He has held visiting faculty appointments at Stanford University, Katholieke Universiteit Leuven, and Xi’an Jiaotong University.  He is an elected Fellow of the ASME, the American Association for the Advancement of Science, and IEEE. He was a co-recipient of ASME Curriculum Innovation Award (1999), Inventor Recognition Award from the Semiconductor Research Corporation (2001), the ASME Electronic and Photonic Packaging Division Outstanding Contribution Award in Thermal Management (2006), ASME J. of Electronics Packaging Best Paper of the Year Award (2008), IBM Faculty Award (2008), IEEE SemiTherm Significant Contributor Award (2009), IIT Kanpur Distinguished Alumnus Award (2011), ASME InterPack Achievement Award (2011), ITherm Achievement Award (2012), ASME Heat Transfer Memorial Award (2013), and AIChE Donald Q. Kern Award (2018).

http://s.uconn.edu/meseminar3/11/22

Abstract: The extracellular matrix (ECM) guides cells through mechanical and soluble signals among others. We guide cell behaviors using these two aspects of ECM.  Even the bone ECM is soft after de-mineralization. Thus, we are interested in soft polymeric materials. Many tissues in our body are elastic including blood vessels, our target tissue. We design elastomers for vascular grafts. The hosts transform the degradable grafts into autologous vascular conduits within a few months, performing the duties of a native artery. On soluble factors, we mimic the anchorage of cytokines in the ECM with heparin-based coacervate. The coacervate extends the bioactivity of many cytokines and growth factors. This controlled release platform shows promise in promoting angiogenesis and controlling immune activities. We are currently exploring how these materials perform in preclinical models, with robust rodent data and early large animal data.

Biographical Sketch: Yadong Wang is the McAdam Family Foundation Professor of Heart Assist Technology at Cornell University. He obtained his Ph.D. degree at Stanford University in 1999, performed his postdoctoral studies at MIT, and joined the Georgia Institute of Technology in 2003 as an assistant professor. He was recruited to University of Pittsburgh in 2008 and subsequently to Cornell in 2017. He has published on topics ranging from Chemistry, Materials Science to Biomedical Engineering in journals including Science, Nature Biotechnology, Nature Medicine, and PNAS.  Several of his inventions are licensed, one polymer he invented is now commercially available and approved for clinical use. He co-founded three companies to translate the technologies developed in his laboratory. His research focuses on creating biomaterials for unmet clinical needs in soft tissues. His team enjoys collaboration with others who share the same passion for translational research.

http://s.uconn.edu/meseminar2/25/22

Abstract: Energy conversion and propulsion systems operating with a lean, premixed mode of combustion are advantageous in terms of both emissions and economics. This is because fully premixing fuel and oxidizer prior to combustion can reduce harmful exhaust levels, while operating fuel lean ensures complete fuel consumption, providing superior fuel economy. In fact, it is often preferred to operate a system as lean as possible; however, there is a limit to how little fuel must be added to a system to facilitate self-sustained combustion. This limit is termed lean blow off (LBO). One mechanism for avoiding LBO is to generate a recirculating flow, which provides 1) a low-velocity region for flames to reside in, and 2) a constant ignition source for the injected reactants. Flow obstructions, like bluff bodies, are often used to produce such recirculating flows. While the LBO limits of premixed bluff-body stabilized flames have been extensively explored, such studies have primarily considered flames operating at atmospheric pressures. Yet, most combustion systems operate at elevated pressures. Thus, there is a need to assess the influence of elevated pressure on the LBO limits of turbulent premixed bluff-body stabilized flames.

This work addresses that need by measuring the LBO limits of such flames while they were operated within an optically accessible pressure chamber. In this study, the operating pressures and bulk flow velocities (U) ranged between 1 and 3 bar and 5 and 50 m/s, respectively. Key observations included the discovery of two stability regimes: one at atmospheric conditions and those with elevated pressure and U < 20 m/s (regime-a), and another at elevated pressures with U < 20 m/s (regime-b). Flames in regime-a were found to be more stable (i.e., their LBO limits occurred at lower fuel-to-air ratios) than those in regime-b. Yet, within both regimes, the LBO limits were found to be insensitive to operating pressure. To elucidate the reason for these observations, advanced laser-based diagnostics were implemented to probe the flames’ structure and to visualize the turbulent flow fields interacting with them. Ultimately, such results provide a phenomenological explanation for the observed behaviors and highlight the fact that explanations and scaling laws derived from measurements at atmospheric conditions cannot always be extrapolated to those at elevated pressures.

Biographical Sketch: Aaron Skiba is an Aerospace Research Engineer in the Combustion Branch of the Turbine Division at the Air Force Research Laboratory (AFRL) in Dayton, Ohio. His current research efforts focus on the experimental assessment of combustion processes occurring under conditions relevant to practical propulsion systems. Such efforts include fundamental studies of liquid-fueled flames subjected to large turbulences levels, the optimization of advanced optical diagnostics to enable such studies, and the development of algorithms to facilitate fair comparisons between experimental and numerical results.

Prior to joining AFRL, Aaron was a postdoc at the Naval Research Laboratory (NRL) where his research efforts focused on experimental studies high-speed spray flames. Such studies included high-speed (>50 kHz) droplet imaging measurements to assess atomization and breakup processes, as well as coherent anti-Stokes Raman spectroscopy (CARS) to obtain temperature profiles. Additionally, while at NRL, Aaron utilized rotational Raman scattering of H2 to measure the temperature of the exhaust issuing from a micro-thruster that was operated within a large vacuum chamber.

Before his postdoc at NRL, Aaron served as a Research Associate in Professor Epaminondas Mastorakos’ group in the Department of Engineering at the University of Cambridge. There, he was involved in an array of experimental studies that included: 1) assessing the lean blow-off (LBO) limits of turbulent premixed bluff-body stabilized flames with either complex fuels at atmospheric conditions or with simple fuels at elevated pressures; 2) exploring the dynamics of ignition and LBO of premixed flames in a full annular combustor; and 3) employing laser-based imaging techniques to elucidate the effects that turbulence, fuel-type, and dilution levels have on the production and oxidization of soot within model aero-engines.

Aaron received his Bachelors, Masters, and Ph.D. degrees from the Department of Aerospace Engineering at the University of Michigan. During his Ph.D., which was supervised by Professor James F. Driscoll, Aaron studied the effects extreme turbulence levels have on the structure and dynamics of premixed flames. Furthermore, a significant portion of his dissertation research was carried out in collaboration with Dr. Campbell D. Carter at AFRL. During those collaborations, Aaron assisted Dr. Carter with the application of an array of state-of-the-art, laser-based diagnostics to highly turbulent premixed flames, the most notable of which involved the simultaneous acquisition of stereo-PIV data with PLIF images of CH2O and OH at a rate of 20 kHz.

Overall, Aaron’s interests lie in optimizing and utilizing advanced laser-based and imaging diagnostics to understand the fundamental physics of flow-chemistry interactions. Ultimately, this understanding will facilitate the development of accurate yet computationally tractable models for predicting the dynamics of turbulent reacting flows.

http://s.uconn.edu/meseminar1/28/22

Abstract: Bone is strong, tough yet lightweight, which can be attributed to its complex hierarchical structures across multiple length scales. The factors contributing to these superior properties are still not completely understood, especially its structure at the sub-micron- and nano-scales. The morphology and mechanical properties of bone are also affected by diseases and treatment. This study presents the results of combined experimental and computational studies of the mechanical behaviors and structures of bone across multiple length scales. Mechanical testing coupled with micro X-ray computed tomography (micro-CT) enabled concurrent non-invasive characterization of 3D full-field bone microstructures and bone mechanical properties. Atomic force microscopy (AFM) was used to map the surface morphology and elastic properties of microscale structures (cement line and sub-lamellae) and nanoscale ultrastructure (mineralized collagen fibril (MCF) and extrafibrillar matrix (EFM)) in bone. The experimental results are integrated with computational models. The results provided a better understanding of the structure and the mechanical behaviors of bone across multiple length scales, laid the foundation for the bio-inspired design of new materials, and shed light on the improvement of implant treatment.

 

Biographical Sketch: Dr. Jing Du is an Assistant Professor of Mechanical Engineering at Penn State University. She received her B.S. and M.S. degrees in Mechanical Engineering and Materials Science and Engineering, respectively, from Tsinghua University and a Ph.D. degree in Mechanical and Aerospace Engineering from Princeton University. Before joining Penn State, she was a postdoctoral scholar in the School of Dentistry at the University of California, San Francisco (UCSF). Her current areas of research interests include mechanical behaviors of biological tissues and biomaterials, biomedical devices, and bio-inspired design.

http://s.uconn.edu/meseminar1/21/22

Abstract: Recent advances in electronics enable powerful biomedical devices that have greatly reduced therapeutic risks by monitoring vital signals and providing means of treatment.  Conventional electronics today form on the planar surfaces of brittle wafer substrates and are not compatible with complex body tissues.  Soft and implantable devices can help us better understand the behavior and effects of various diseases.  This talk presents the challenges, design strategies, and novel fabrication processes behind a potential medical device that (a) integrates with human physiology, and (b) dissolves completely after its effective operation.  The integration of the deformable multimodal sensing platform with stretchable antennas, micro-supercapacitor arrays, and energy harvesting modules further yields a self-powered stretchable wireless sensing system for next-generation bio-integrated electronics and environmental sensing.

Biographical Sketch: Dr. Huanyu “Larry” Cheng is an Assistant Professor of Engineering Science and Mechanics with courtesy appointments in the Department of Biomedical Engineering, Department of Mechanical Engineering, Department of Architectural Engineering, Department of Industrial and Manufacturing Engineering, and the Department of Materials Science and Engineering at Penn State University. His research group focuses on the design, fabrication, and application of stretchable and dissolvable multimodal sensors for biomedicine. Larry has co-authored more than 100 peer-reviewed publications with total citations >13,000 and an H-index of 46 according to Google Scholar. His work has been recognized through the reception of numerous awards, including the 2022 Minerals, Metals & Materials Society (TMS) Functional Materials Division (FMD) Young Leaders Professional Development Award, the 2021 NIH Trailblazer Award, 2021 Scialog Fellow in Advancing BioImaging, 2021 Frontiers of Materials Award from TMS, First and Second Place in the Ben Franklin TechCelerator Pitch in 2020 and 2021, respectively, ACS Petroleum Research Fund New Investigator in 2018, Forbes 30 Under 30 Science category in 2017, elected member of the Global Young Academy for scientists under age 40 in 2016, among others. He also serves as the associate editor for 7 journals and reviewer for 185 international journals.

http://s.uconn.edu/meseminar12/10/21

Abstract: Hydrogels, highly hydrated cross-linked polymer networks, have emerged as powerful synthetic analogs of extracellular matrices for basic cell studies as well as promising biomaterials for regenerative medicine applications. A critical advantage of these synthetic matrices over natural networks is that bioactive functionalities, such as cell adhesive sequences and growth factors, can be incorporated in precise densities while the substrate mechanical properties are independently controlled. We have engineered poly(ethylene glycol) [PEG]-maleimide hydrogels for local delivery of therapeutic proteins and cells in several regenerative medicine applications. For example, synthetic hydrogels with optimal biochemical and biophysical properties have been engineered to direct human stem cell-derived intestinal organoid growth and differentiation, and these biomaterials serve as injectable delivery vehicles that promote organoid engraftment and repair of intestinal wounds. In another application, hydrogels presenting immunomodulatory proteins induce immune acceptance of allogeneic pancreatic islets and reverse hyperglycemia in models of type 1 diabetes. Finally, injectable hydrogels delivering anti-microbial proteins eradicate bone-associated bacterial infections and support bone repair. These studies establish these biofunctional hydrogels as promising platforms for basic science studies and biomaterial carriers for cell delivery, engraftment and enhanced tissue repair.

Biographical Sketch: Andrés J. García is the Executive Director of the Petit Institute for Bioengineering and Bioscience and Regents’ Professor at the Georgia Institute of Technology. Dr. García’s research program integrates innovative engineering, materials science, and cell biology concepts and technologies to create cell-instructive biomaterials for regenerative medicine and generate new knowledge in mechanobiology. This cross-disciplinary effort has resulted in new biomaterial platforms that elicit targeted cellular responses and tissue repair in various biomedical applications, innovative technologies to study and exploit cell adhesive interactions, and new mechanistic insights into the interplay of mechanics and cell biology. In addition, his research has generated intellectual property and licensing agreements with start-up and multi-national companies. He is a co-founder of 3 start-up companies (CellectCell, CorAmi Therapeutics, iTolerance). He has received several distinctions, including the NSF CAREER Award, Young Investigator Award from the Society for Biomaterials, Georgia Tech’s Outstanding Interdisciplinary Activities Award, the Clemson Award for Basic Science from the Society for Biomaterials, the International Award from the European Society for Biomaterials, and Georgia Tech’s Class of 1934 Distinguished Professor Award. He is an elected Fellow of Biomaterials Science and Engineering (by the International Union of Societies of Biomaterials Science and Engineering), Fellow of the American Association for the Advancement of Science, Fellow of the American Society of Mechanical Engineers, and Fellow of the American Institute for Medical and Biological Engineering. He served as President for the Society for Biomaterials in 2018-2019. He is an elected member of the National Academy of Engineering, the National Academy of Medicine, and the National Academy of Inventors.

http://s.uconn.edu/meseminar12/3/21

Abstract: Internet of things (IoT), robotics, big data and artificial intelligence (AI) hold the key to Industry 4.0, which is identified as cyber-physical systems. To stay relevant in the AI age, humans must collaborate with robots or even merge with electronics and machines to realize internet of health (IoH), augmented reality (AR), and augmented human capabilities. However, bio-tissues are soft, curvilinear and dynamic whereas conventional electronics and machines are hard, planar, and rigid. Over the past two decades, soft electronics blossom as a result of new materials, novel structural designs, and digital manufacturing processes. This talk will discuss our research on the design, fabrication, conformability, and functionality of soft bio-integrated and bio-mimetic electronics based on inorganic functional materials such as metals, silicon, carbon nanotubes (CNT), and graphene. In particular, epidermal electronics, a.k.a. electronic tattoos (e-tattoos) represent a class of noninvasive stretchable circuits, sensors, and stimulators that are ultrathin, ultrasoft and skin-conformable. My group has invented a dry and freeform “cut-solder-paste” method for the rapid prototyping of multimodal, wireless, or very large area e-tattoos that are also high-performance and long-term wearable. The e-tattoos can be applied for physiological sensing and prosthesis/robot control. Recently, we have also engineered e-skins based on electrically conductive porous nanocomposite. The hybrid piezoresistive and piezocapacitive responses of this novel e-skin has enabled high pressure sensitivity over wide pressure ranges. It therefore could be applied for not only mechanophysiological sensing, but also soft robotics undergoing large deformations. A perspective on future opportunities and challenges in this field will be offered at the end of the talk.

 Biographical Sketch: Dr. Nanshu Lu is currently Temple Foundation Endowed Associate Professor at the University of Texas at Austin. She received her B.Eng. from Tsinghua University, Beijing, Ph.D. from Harvard University, and then Beckman Postdoctoral Fellowship at UIUC. Her research concerns the mechanics, materials, manufacture, and human / robot integration of soft electronics. She has been named 35 innovators under 35 by MIT Technology Review (TR 35). She has received US NSF CAREER Award, US ONR and AFOSR Young Investigator Awards, 3M non-tenured faculty award, and iCANX/ACS Nano Inaugural Rising Star Lectureship. She has been selected as one of the five great innovators on campus and five world-changing women at the University of Texas at Austin. She is named a highly cited researcher by Web of Science. For more information, please visit Prof. Lu’s research group webpage at https://sites.utexas.edu/nanshulu/.

http://s.uconn.edu/meseminar11/12

Abstract: This talk presents a manufacturability-driven, multi-component topology optimization (MTO) framework for simultaneous design and partitioning of structures assembled of multiple components. Constraints on component geometry imposed by chosen manufacturing processes are incorporated in the conventional density-based topology optimization, with additional design variables specifying fractional component membership that enables continuous relaxation of otherwise discrete partitioning problems.  The geometric constraints imposed by various manufacturing processes, such as size, perimeter length, undercut, and enclosed cavities, are also relaxed to enable the manufacturability evaluation of “gray” geometries that occur during the density-based topology optimization. Examples on minimum compliance structural assembly design for sheet metal stamping (MTO-S), die casting (MTO-D), additive manufacturing (MTO-A), and continuous fiber printing process (MTO-C) show promising advantages over the conventional monolithic topology optimization.  In particular, manufacturing constraints previously applied to monolithic topology optimization gain new interpretations when applied to multi-component assemblies, which can unlock richer design space for topology exploration.  The talk will conclude with a brief overview of the latest developments towards the MTO framework for foldable “4D” printed structures.

Biographical Sketch: Kazuhiro Saitou is a Professor of Mechanical Engineering at the University of Michigan, Ann Arbor, Michigan, USA. He currently serves for the Department as an Associate Chair for Graduate Education. He received BEng degree from University of Tokyo, Japan, and MS and PhD degrees from the Massachusetts Institute of Technology (MIT), USA. His research interest includes algorithmic and computational design synthesis and design for manufacture and assembly, with applications in mechanical, industrial, and biomedical systems.  He is a Fellow of ASME and IEEE.