Penn Engineering Events

CIS Seminar: "Contesting Secure Development to Understand Security Mistakes"
2019-11-05 15:00 - 16:00 (America/New_York) | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
With the ongoing, frequent disclosure of the existence and exploitation of security vulnerabilities, one might wonder: How can we can build software that is more secure? In an attempt to focus educational attention on this question, and gather empirical evidence at the same time, we developed the Build it, Break it, Fix it (BIBIFI) security-oriented programming contest. In BIBIFI, teams aim to build specified software that should be correct, efficient, and secure. These goals mimic those of the real world. Security is tested when teams attempt to break other teams’ submissions. Winners are chosen from among the best builders and the best breakers. BIBIFI was designed to be open-ended — teams can use any language, tool, process, etc. that they like.

We ran three 6-week contests involving a total of 156 teams from across the world, and three different programming problems. Most participants had previous development experience and security education. Quantitative analysis from these contests found several interesting trends. For example, the most efficient build-it submissions used C/C++, but submissions coded in a statically-type safe language were 11× less likely to have a security flaw than C/C++ submissions. A manual, in-depth qualitative analysis (using iterative open coding) of the vulnerabilities in 76 of these projects also revealed interesting trends. For example, the analysis found that simple mistakes were least common: only 26% of projects introduced such an error. Conversely, vulnerabilities arising from a misunderstanding of security concepts were significantly more common: 84% of projects introduced at least one such error. Overall, our results have implications for improving secure-programming language choices, API designs, API documentation, vulnerability-finding tools, and security education.

This is joint work with James Parker, Andrew Ruef, Dan Votipka, Kelsey Fulton, Matthew Hou, Michelle Mazurek, and Dave Levin, all at the University of Maryland

ESE Seminar: "Metasurface Computational Imaging"
2019-11-05 11:00 - 12:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Modern image sensors consist of systems of cascaded and bulky spherical optics for imaging with minimal aberrations. While these systems provide high-quality images, the improved functionality comes at the cost of increased size and weight. One route to reduce a system’s complexity is via computational imaging, in which much of the aberration correction and functionality of the optical hardware is shifted to post-processing in the software realm. Alternatively, a designer could miniaturize the optics by replacing them with diffractive optical elements, which mimic the functionality of refractive systems in a more compact form factor. Metasurfaces are an extreme example of such diffractive elements, in which quasiperiodic arrays of resonant subwavelength optical antennas impart spatially-varying changes on a wavefront. While separately both computational imaging and metasurfaces are promising avenues toward simplifying optical systems, a synergistic combination of these fields can further enhance system performance and facilitate advanced capabilities. In this talk, I will present a method to combine these two techniques to perform full-color imaging across the whole visible spectrum [1]. I will also discuss the use of computational techniques to design new metasurfaces [2], and using metasurfaces to perform computation on wavefronts, with applications in optical information processing and sensing.

Figure: (a) Hybrid cubic-quadratic metasurface; (b) Using the metasurface and computational imaging we demonstrated full-color imaging; (c) We developed inverse design methodologies for metasurfaces made of dielectric spheres.
References: [1] S. Colburn, A. Zhan, and A. Majumdar, “Metasurface optics for full-color computational imaging,” Science Advances, vol. 4, 2018. [2] A. Zhan, T. K. Fryett, S. Colburn, and A. Majumdar, “Inverse design of optical elements based on arrays of dielectric spheres,” Applied Optics, vol. 57, pp. 1437-1446, 2018/02/20 2018.

MEAM Seminar: "Multi-Stable Morphing Structures"
2019-11-05 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Variable geometry “morphing” structures can achieve different geometric configurations through overall deformation, but usually many actuators are required for shape control. In this talk we consider a particular type of morphing structure that is able to switch configuration with only a few actuators. It is based on the concept of embedding by design local energy minima in the configuration space of the structure. A general bar and plate structure connected by frictionless hinges can be made locally stable in a set of chosen target configurations by attaching extensional and rotational springs to the structure. The unstressed lengths and angles of the springs, as well as their stiffnesses, are the design parameters. We present a general theory to formulate the required equilibrium and stability conditions. Solutions of these equations provide specific values of the spring properties that correspond to local energy minima in all of the target configurations. Applications to reconfigurable antennas are also presented.

PICS Seminar: "High-order Spectral Difference Method for Studying Marine Hydrodynamics and Thermal Convection and Magneto-hydrodynamics for the Sun"
2019-11-01 14:00 - 15:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract
Two recent advancements of high-order spectral difference (SD) method for computational fluid dynamics on unstructured meshes will be presented. The first progress is our contribution to a new curved sliding-mesh approach to the SD method for simulating flapping and rotary wing aerodynamics. The second elevation of the SD method is our recent successful design of a massively parallel code, namely CHORUS, for predicting thermal convection in the Sun. Recently, we have also built a simulation capability for predicting magnetohydrodynamics of the Sun.

MEAM Special Seminar: "Smartphone-based Mobile Detection Platform for Molecular Diagnostics: from Infectious Diseases to Cancer"
2019-10-31 14:00 - 15:00 | Towne 227 (MEAM Conference Room), 220 S. 33rd Street, Philadelphia, PA, 19104, United States
Rapid, quantitative molecular diagnostics in the field, at home, and in resource poor settings is needed for evidence-based disease management, control, and prevention. Conventional molecular diagnostics requires extensive sample preparation, sophisticated instruments, and trained personnel, restricting their use to centralized laboratories. To overcome the limitations of laboratory-based procedures, we designed a simple, inexpensive, hand-held, smartphone-based mobile detection platform “smart-connected cup”, for rapid, connected, and quantitative detection of pathogens’ nucleic acids. More recently, we have been expanding our technology platform to include detection of rare cancer biomarkers in body fluids for cancer screening and individualized therapy. To overcome the challenge of identifying very low concentrations of mutant alleles within a large background of very similar wild type nucleic acids, we are using programmable enzymes to cleave wild type alleles and improve signal to noise ratio. We anticipate that our methods will improve quality of health care in regions lacking sophisticated laboratories and enable patients to assume greater responsibility for their care.

MSE Seminar: "Managing Intercultural Interactions in a Challenging Global Higher Education Landscape"
2019-10-31 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
The rapidly diversifying face of colleges and universities in the United States including the University of Pennsylvania require that we are able to manage intercultural relationships from different backgrounds. We are all working in a multicultural institution, with students, faculty and staff from all over the world. This makes for a very diverse, vibrant community – and at times, a rather confusing one. This session will promote intercultural competence, cultural humility and heighten cross-cultural awareness. You will engage in a presentation and discussion about culture, values, perceptions, and communication styles and cultural patterns of thought and behavior that will help you understand the basic concepts, theories and issues of intercultural communication related to intercultural relationships and how these concepts apply to your personal and professional lives.

CBE Seminar: "Chemical Reactor Scale-Up: Principles and Practice at Dow”
2019-10-30 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Since Dow first formed a global reaction engineering discipline over twenty years ago, we have accumulated much experience leading and supporting a diversity of reaction engineering projects for our corporation. This presentation will provide specific examples of real-world reaction engineering problems at Dow in the past 27 years and summarize our perspective regarding the key tools and methods of the well-equipped industrial reaction engineering laboratory. Several brief anecdotal descriptions of past process development and reactor scale-up projects will highlight important lessons learned on this journey. In addition, this talk will demonstrate the role of reaction engineering fundamentals and methodologies in shaping projects, enabling decisions, and empowering teams to succeed. Over the years, we have used a wide array of laboratory hardware and computer software tools. In some cases, we have developed our own tools; in other cases, we have chosen to use commercially available offerings to meet our experimental and computational needs. This presentation will highlight the reaction engineering tools and best practices that have stood the test of time and close with a brief list of some of the capability gaps that remain.

Sigma Aldrich Lecture: "Epitaxy by Design: Epitaxial Growth of Dissimilar Materials"
2019-10-30 11:00 - 12:00 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: The ability to integrate dissimilar materials with different crystal structures and properties enables heterostructures to be developed with new functionality well beyond the normal band gap engineering offered by semiconductor heterostructures. The combination of metals, semiconductors, insulators, magnetic, piezoelectric, structural and phase change materials offers the potential for nearly limitless control of device properties. Heusler compounds, for example, are of great interest due to their multifunctional properties including metallic, ferromagnetic, half metallic, semiconducting and potentially topological properties. Heterostructures of ferromagnetic materials with insulators and semiconductors have revolutionized spintronic devices.
Semiconductors are an ideal choice for substrates for dissimilar materials epitaxial growth because of their wide range of lattice parameters, high quality, readily controlled electrical and optical properties and the availability of large area substrates at a reasonable cost. The control of strain and lattice matching, interfacial bonding and reactions is important for the growth and properties of dissimilar materials heterostructures.
In this presentation, results for the molecular beam epitaxial growth of metallic compound/III-V semiconductor heterostructures with designer properties will be discussed. High efficiency electrical spin injection and detection in magnetic Heusler/GaAs contacts, tuning of the spin polarization, as well as the ability to tune the electronic and magnetic properties of Heusler compounds through alloying will be presented. The focus of the presentation will be on understanding the growth and properties of dissimilar materials with emphasis on Heusler compound/III-V compound semiconductor heterostructures. These studies have aimed at tailoring of interfacial and material properties of these dissimilar materials heterostructures for targeting novel applications including spintronics and topological quantum computing.

ESE Seminar: "Solid-State Spin-Photon Interfaces: Old Friends & New"
2019-10-29 11:00 - 12:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract : Optically active spins in solids offer exciting opportunities as scalable and feasible quantum-optical devices. Numerous material platforms including diamond, semiconductors, and atomically thin 2d materials are under investigation, where each platform brings some advantages of control and feasibility along with other challenges. The inherently mesoscopic nature of solid-state platforms leads to a multitude of dynamics between spins, charges, vibrations and light. Implementing a high level of control on these constituents and their interactions with each other creates exciting opportunities for realizing stationary and flying qubits within the context of spin-based quantum information science, as well as investigating mesoscopic quantum systems. Quantum optics, developed originally for atomic systems, provides a very valuable toolbox for this endeavour. In this talk, I will provide a snapshot of the progress and challenges for two contrasting examples for spin-photon interfaces, namely semiconductor quantum dots and confined excitons in atomically thin materials. For the former, I will focus on a method to suppress the magnetic noise of the nuclear ensemble by an effective cooling mechanism. This method yields access to the nuclear sideband resolved regime and coherent coupling between a single electron spin and the nuclear ensemble. For the latter, I will discuss ways to deterministically trap long-lasting confined excitons acting as artificial atoms, as well as their integration into opto-electronic devices.

MEAM Seminar: "The Simulation and Modeling of Turbulent Flows"
2019-10-29 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Our group at the University of Minnesota focuses on fundamental advances in numerical algorithms, and understanding of flow physics that allow the prediction of engineering turbulent flows. This presentation will discuss key aspects of such simulation alongside illustrative examples. We will discuss a recently developed unstructured overset grid methodology and its application to particle-resolved DNS of several thousands of particles in turbulent flow. We will discuss global stability and adjoint analyses for three-dimensional complex baseflows, and illustrate its application to jets in crossflow. Finally we will present an integral analysis for axisymmetric boundary boundary layers in the presence of pressure gradients, and illustrate its application to interpret LES results.

PSOC Seminar : "Single-Cell Analysis of Differentiation and Drug Response in Glioblastoma"
2019-10-28 12:00 - 13:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States

ESE Doctoral Dissertation Defense: "IMU-Based State Estimation and Control of Quadrotors Leveraging Aerodynamic Effects"
2019-10-28 11:00 - 12:30 | Room 307, Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: Quadrotors and multirotors in general are common in many inspection and surveillance applications. For these applications, visual-inertial odometry is a common way to localize the vehicles and observe the environment. However, unlike with wheeled mobile robots, quadrotor localization algorithms often do not use knowledge of the control inputs and the full vehicle dynamics as a process model for localization. Rather, they use kinematic models, with the IMU providing acceleration and angular velocity. One of the reasons for avoiding the use of dynamics is that, until recently quadrotor aerodynamic effects have not been considered in the literature and hence the dynamic models for quadrotors have been less accurate than those for wheeled mobile robots. The main aerodynamic terms that are significant are first-order effects that are linear in velocity and angular velocity. They are predominantly caused by aerodynamic interaction with the spinning propellers. This work investigates the models for such effects, as well as what can be gained if such aerodynamic effects are incorporated into the dynamic model and the full dynamics are used for state estimation. We develop novel IMU-based filters, the end results of which are used to estimate the wind velocity of the quadrotor or, indoors, when the ambient wind is zero, the velocity of the quadrotor. In addition, these filters estimate the many aerodynamic parameters in the model online. They may also be used to estimate sensor biases and inertial parameters. We demonstrate the effectiveness of these filters through experiments. We also present nonlinear observability analyses that theoretically determine the observability properties of the systems.
Committee Members:
Vijay Kumar, Nemirovsky Family Dean of Engineering
Ani Hsieh, Research Associate Professor, MEAM
Kostas Daniliidis, Ruth Yalom Stone Professor, CIS
Camillo J. Taylor, Professor, CIS
Giuseppe Loianno, Associate Professor, NYU ECE

PRiML Seminar: "Nonconvex Optimization Meets Statistics: A Few Recent Stories"
2019-10-25 15:00 - 16:00 | Room 401B, 3401 Walnut, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Recent years have seen a flurry of activity in solving statistical estimation and learning problems via nonconvex optimization. While conventional wisdom often takes a dim view of nonconvex optimization algorithms due to their susceptibility to spurious local minima, simple iterative methods such as gradient descent have been remarkably successful in practice. The theoretical footings, however, had been largely lacking until recently. This talk presents two recent stories about nonconvex statistical estimation, which highlight the important role of statistical models in enabling efficient nonconvex optimization. The first story is about randomly initialized nonconvex methods for a phase retrieval problem: even without careful initialization, simple algorithms like gradient descent provably find the global solution within a logarithmic number of iterations. The second story is concerned with uncertainty quantification for nonconvex low-rank matrix completion. We develop a de-biased estimator — on the basis of a nonconvex estimate — that enables optimal construction of confidence intervals for the missing entries of the unknown matrix. All of this is achieved via a leave-one-out statistical analysis framework, which is very powerful in handling and decoupling complicated statistical dependency.

This is joint work with Cong Ma, Yuling Yan, Yuejie Chi, and Jianqing Fan.

PICS Seminar: Isogeometric Methods for Solids, Structures, and Fluid-Structure Interaction: From Early Results to Recent Developments
2019-10-25 14:00 - 15:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: This presentation is focused on Isogeometric Analysis (IGA) with applications to solids and structures, starting with early developments and results, and transitioning to more recent work. Novel IGA-based thin-shell formulations are discussed, and applications to progressive damage modeling in composite laminates due to low-velocity impact and their residual-strength prediction are shown. Fluid–structure interaction (FSI) employing IGA is also discussed, and a novel framework for air-blast-structure interaction (ABSI) based on an immersed approach coupling IGA and RKPM-based Meshfree methods is presented and verified on a set of challenging examples. The presentation is infused with examples that highlight effective uses of IGA in advanced engineering applications.

MSE Seminar: “Scalable Multifunctional Nanoarchitectures for Energy Storage”
2019-10-24 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States

CBE Seminar: "Toward Platinum-free Fuel Cells for Affordable Zero-emission Vehicles”
2019-10-23 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
One of the grand challenges facing humanity today is the development of an alternative energy system that is safe, clean, and sustainable. A Distributed Renewable Electrochemical Energy and Mobility System (DREEMS) can meet this challenge. At the foundation of this new energy system, we have chosen to study fuel cells, electrolyzers, and flow batteries. For all these devices polymer electrolytes play a critical role in controlling their performance, cost, and durability, and thus their economic viability. In this presentation, I will focus on our recent work on Hydroxide Exchange Membrane Fuel Cells (HEMFCs). More specifically, I will focus on our recent discovery of a new family of polymer hydroxide (and other anions) conductors that is chemically stable, ionically conductive, and mechanically robust; and HEMFCs with this new class of polymers showed record fuel cell performance and stability at 95 ºC. I will also briefly introduce a new class of crystalline porous polymers that are the most stable among all crystalline porous materials.

ESE Seminar: "Foundations of Deep Learning and Applications in Medicine"
2019-10-23 12:00 - 13:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: Recent advances in machine learning, computer vision, natural language processing, and robotics, offer a tremendous opportunity to transform medicine, from reactive and hospital centered to proactive and patient-centered. To fulfill this promise, new methods need to be developed which are more interpretable, can handle data at multiple spatial and temporal scales, and are robust to data heterogeneity and limited amounts of annotations. The first part of this talk will overview our recent work on the theory of deep learning, including sufficient conditions to guarantee that local minima are globally optimal, as well as an analysis of the optimization and regularization properties of dropout. The second part of this talk will overview our recent work on the development of methods for interpreting biomedical datasets arising in blood cell analysis, regenerative medicine, digital pathology, brain imaging, surgery and rehabilitation therapy.

CIS Seminar: “Learning in dynamic environments”
2019-10-22 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
In many online systems participants use data and algorithms to experiment and learn how to best use the system. Examples include traffic routing as well as online auctions. Game theory classically studies Nash equilibrium as the outcome of selfish interaction, and has many examples illustrating that selfish behavior can lead to suboptimal outcome for all participants. Over the last decade, we developed good understanding how to quantify the impact of strategic user behavior on overall performance in Nash equilibria of games. In this talk we will focus on games where players use a form of learning that helps them adapt to the environment. We ask if the quantitative guarantees obtained for Nash equilibria extend to such out of equilibrium game play, possibly even in dynamically changing environments?

CBE Thesis Defense: "A Heterogeneous and Multiscale Modeling Framework to Develop Patient-Specific Pharmacodynamic System Models in Cancer"
2019-10-22 14:00 - 16:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Thesis Committee: Ravi Radhakrishnan, Ph.D., advisor; Dennis Discher, PhD; Scott Diamond, PhD; and Wei Guo, PhD

MEAM Seminar: "Architecture in Biological Materials: A Template for Toughness Enhancement, or a Siren Song?"
2019-10-22 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Structural biological materials, such as animal bones and shells, display remarkable mechanical properties despite being composed of quite simple and ordinary constituent materials. For example, the toughness of nacre, a structural biological material found in the shells of some mollusks, is orders of magnitude higher than that of its primary constituent—the calcium based mineral aragonite. A number of structural biological materials that display toughness enhancement also possess a lamellar architecture consisting of alternating layers of ceramic and organic phases. It is believed that a structural biological material’s intricate architecture—the geometric arrangement of these phases—is responsible for the observed property enhancements. Within the bio-mimetics community, there is currently great interest in reproducing these architectures in synthetic materials using micro-fabrication and 3D printing in order to achieve the property enhancements observed in structural biological materials.
In this talk I will present experimental and computational mechanics results that show that correctly identifying the connection between a structural biological material’s architecture and any property enhancements can be a very delicate process. Specifically, I will present experiments that characterize the toughness properties of the skeletal elements of the marine sponge Euplectella aspergillum, called spicules. I will show that despite possessing a lamellar architecture that is very similar to that seen in nacre, the spicules do not display a significant toughness enhancement. Through mechanics modeling, I argue that the spicule’s lamellar architecture is connected to their ability to bend more without failing, i.e., to their strength, rather than their toughness. These results serve as a reminder that any efforts aimed at reproducing a structural biological material’s architecture and property enhancements in synthetic materials should be prefaced by a careful investigation of the structural biological material itself.
References
[1] Monn, Michael A., James C. Weaver, Tianyang Zhang, Joanna Aizenberg, and
Haneesh Kesari. “New functional insights into the internal architecture of the
laminated anchor spicules of Euplectella aspergillum.” Proceedings of the National
Academy of Sciences 112, no. 16 (2015): 4976-4981.
[2] Monn, Michael A., and Haneesh Kesari. “A new structure-property connection in
the skeletal elements of the marine sponge Tethya aurantia that guards against
buckling instability.” Scientific reports 7 (2017): 39547.

EWaste Collection
2019-10-22 10:00 - 14:00 | Lobby and Mezzanine, Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
We will be collecting EWASTE items in Levine Lobby on Tuesday in support of Energy Week @ Penn campaign.
This is a great opportunity to properly recycle non-traditional items such as:

computers & printers
computer accessories (keyboards, mice)
Monitors, TVs, Displays
Mobile phones
household electronics (anything with a plug!)
light bulbs
non-recyclable glass

ESE Seminar: "Information Security for the Connected World"
2019-10-18 15:00 - 16:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: An all-wireless vision connecting billions of devices is finally in sight with the Internet-of-Everything paradigm. This vision entails large networks with dynamic connectivity, ad hoc formation and heterogeneous nodes. Central to be able to integrate all our lives to this massive virtual domain is security and privacy of the information that flows through it. Current wireless systems have security of information as an add-on to current design, and rely on application layer protocols, which have worked well for the scale and the resources of the systems to date. Going forward however, with massive scale formation of networks of asymmetric resources, these protocols involving key exchanges and shared randomness for security may prove to be less than practical.
Securing information at the foundation of system design can alleviate these issues by replacing or strengthening the present cryptographic solutions. This foundational design approach brings us to information theoretic security for the all- connected world. In this talk, we will provide an overview of this approach that relies on local randomness and produces information theoretic security guarantees, e.g, for confidentiality and authentication, utilizing the properties of the transmission medium. We will review the insights that have emerged when information security is included as a design primitive and provide the state of the art directions towards realizing the potential of this approach. We will also introduce models where this approach can be integrated with encryption for nodes with local memory storage.

MSE Seminar: “Science and Applications of Topological Photonics across the Electromagnetic Spectrum”
2019-10-17 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
The 2016 Nobel Prize in Physics was awarded to Kosterlitz, Thouless, and Haldane for their pioneering theoretical work on the novel and counter-intuitive phases of matter that are now referred to as topological phases. Almost half a century after these researchers applied powerful mathematical techniques of topology to condensed matter systems, a new rapidly developing area is taking shape, now in the field of photonics. While very different in many respects from their condensed matter counterparts, topological phases of light share some of their unique properties that make topological photonics particularly suitable for practical applications. Just as the inventors of photonic crystals (often referred to as the “semiconductors of light”) borrowed crucial ideas, such as propagation bands, bandgaps, and Brillouin zone, from condensed matter physics, so do the researchers in the field of topological photonics that attempts to emulate the key concepts from low-dimensional topological materials. Those include photonic topological insulators (PTIs), reflection-less edge states that propagate along the domain walls of the PTIs, and spin-polarized/valley-polarized transport.
In this talk, Dr. Shvets will provide an overview of the field, with special emphasis on the photonic emulation of the canonical quantum topological phases such as the Hall, spin-Hall, and valley-Hall phases. He will then describe how such heterogeneous PTIs can be integrated and used for developing novel devices such as compact circulators. Experimental results demonstrating reflection-less transport of topologically protected edge states will be presented. He will also discuss how the ideas from topological photonics can be used for complete reimagining of the architectures of photonic devices such as add/drop filters, delay lines, and logical gates based on the valley degree of freedom of photons (“photonic valleytronics”). Finally, Dr. Shvets will discuss the prospects of realizing reconfigurable topological photonic structures on a nanoscale. The prospects for exciting topologically protected microwaves using high current beams, and using the latter for high-power magnets-free microwave radiation, will also be discussed.

MSE Special Seminar: “What They Don’t Teach You in School that You Need to Succeed in Life”
2019-10-16 15:00 - 16:30 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States

CBE Seminar: "Examining Heterogeneous Populations of Microbes at the Single Cell Level Using Stabilized Emulsions”
2019-10-16 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Conventional methods in microbiology can be limited by long assay execution and analysis times, large reagent volumes, and high single-use supply costs. These limitations can be overcome using drop-based microfluidics in which picoliter-sized, water-in-oil emulsions serve as independent microreactors, allowing for the compartmentalization of microbes and high-throughput assaying at the single cell level. Here, drop-based microfluidics is used to interrogate the physiological heterogeneity of P. aeruginosa cells in a microbial population using a technique we name DropSOAC (Drop Stabilization On A Chip). The DropSOAC method stabilizes the position and volume of monodisperse water-in-oil drops with diameters <20 mm within a monolayer array on a microfluidic chip for 24 h. The stability of drops is maintained by soaking the device in a reservoir containing both water and oil in thermodynamic equilibrium. This ensures that phase equilibrium of the drop emulsion fluids within the porous PDMS material structure is maintained during drop incubation and imaging. Continuing this work, we aim to study the rapid emergence of antibiotic resistance now observed in common bacterial strains to find effective treatments for persistent bacterial infections. This will be performed using a microfluidic chip that is capable of encapsulating in parallel, 96 barcoded assay samples in drops using fluorescent particles. Using a custom-built microscope that can read fluorescence from drops at rates of thousands per second, we demonstrate sorting for a particular barcode combination from our droplet library. The results presented here show the potential of drop-based microfluidics for high-throughput assaying of heterogeneous populations of microbes at the single cell level.

PSOC Seminar : "Lessons from the Liver: From Chromosome Segregation to Tissue Regeneration"
2019-10-14 12:00 - 13:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States

MEAM Doctoral Dissertation Defense: "Problems in Nonlinear Homogenization: Bounds, Estimates, Macroscopic Instabilities, and Post-Bifurcation Response"
2019-10-11 11:00 - 13:00 | Towne 309, 220 S. 33rd Street, Philadelphia, PA, 19104, United States
This talk is concerned with the use of nonlinear homogenization to study the effective response of composites. We look to illustrate the effect that constitutive assumptions have on the methods by which such estimates can be obtained, as well as on the actual effective, or homogenized, response of the material. Although helpful in ensuring existence in a variational setting, convexity is often inconsistent with certain physical requirements (e.g. objectivity). Such is the case of hyperelasticity, the subject of the first part of the talk. The lack of convexity of the stored-energy functions of such hyperelastic systems has long been known to lead to the development of instabilities. When such instabilities do not result in material failure, we look to study the post-bifurcation behavior of the system. We present a framework for doing so, and compute the post-bifurcation response of a laminated hyperelastic composite explicitly under general three-dimensional loading conditions. In the second part of the talk, we will consider the class of magneto-elastic composites, which consist of hyperelastic materials that are also magnetically susceptible. Unlike in the case of hyperelasticity, there lacks a complete mathematical framework for obtaining the effective response of such materials, and researchers have only begun to investigate the potential for instabilities in these materials. We therefore look to generalize the same methodology used successfully in the purely mechanical context to study the post-bifurcation behavior of magneto-elastic composites. This in part requires a rigorous generalization of the theoretical aspects that underlie the method. With this, we calculate the post-bifurcation response of a magneto-elastic material under general plane-strain loading conditions with a magnetic field applied in the plane of deformation.

BE Doctoral Dissertation Defense: Human organ-on-chip systems for the study of biomechanical forces in health and disease
2019-10-09 15:30 - 17:00 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States

Cultivating Cultures of Ethical STEM: Institutional Transformation and Industrial Research Approaches and Findings
2019-10-08 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
This two-part talk will describe the scope of work and emergent findings of two ongoing National Science Foundation Cultivating Cultures of Ethical STEM (CCESTEM) projects. Each project seeks to provide strategies for the design, assessment, and research of learners’ ethical formation. The first project, an Institutional Transformation CCESTEM project (Award #1737157), seeks to utilize Faculty Learning Communities to refine instructional approaches to the Integrated Community-Engaged Learning and Ethical Reflection (I-CELER) framework among faculty in two departments at Indiana University Purdue University – Indianapolis (IUPUI). The second project, a Standard Research CCESTEM project (Award #1737303), seeks to explore variations in ways of experience ethics among engineering practitioners in the health products industry. Taken together, these projects provide insights for the design of learning environments to foster STEM students’ and practitioners’ ethical dispositions and reasoning skills.

ESE Seminar: "2D Materials for Unconventional Devices: From Flexible/Wearable Tattoo Sensors to Monolayer Memory"
2019-10-08 11:00 - 12:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: This talk will present our latest research adventures on 2D nanomaterials towards greater scientific understanding and advanced engineering applications. In particular the talk will highlight our work on flexible electronics, zero-power devices, monolayer memory (atomristors), non-volatile RF switches, and wearable tattoo sensors. Non-volatile memory devices based on 2D materials are an application of defects and is a rapidly advancing field with rich physics that can be attributed to sulfur vacancies or metal diffusion. Atomistic modeling and atomic resolution imaging are contemporary tools under use to elucidate the memory phenomena. Likewise, from a practical point, electronic tattoos based on graphene have ushered a new material platform that has highly desirable practical attributes including optical transparency, mechanical imperceptibility, and is the thinnest conductive electrode sensor that can be integrated on skin for physiological measurements. Much of these research achievements have been published in nature, IEEE and ACS journals, and widely covered by the news media including Time magazine, BBC, Nature news, IEEE spectrum, and several dozen media outlets.
References:
[1] Akinwande, et al., “Graphene and 2D Materials for Silicon Technology,” Nature, 2019.
[2] X. Wu, R. Ge, P.-A. Chen, H. Chou, Z. Zhang, Y. Zhang, S. Banerjee, M.-H. Chiang, J. C. Lee, and D. Akinwande, “Thinnest Nonvolatile Memory Based on Monolayer h-BN,” Advanced Materials, p. 1806790, 2019.
[3] M. Kim, R. Ge, X. Wu, X. Lan, J. Tice, J. C. Lee, and D. Akinwande, “Zero-static power radio-frequency switches based on MoS2 atomristors,” Nature Communications, vol. 9, p. 2524, 2018.
[4] S. Kabiri Ameri, R. Ho, H. Jang, L. Tao, Y. Wang, L. Wang, D. M. Schnyer, D. Akinwande, and N. Lu, “Graphene Electronic Tattoo Sensors,” ACS Nano, vol. 11, 2017.
