ASSET Seminar: "Efficient and Targeted COVID-19 Border Testing Via Reinforcement Learning" (Hamsa Bastani, Penn)
2023-09-13 12:00 - 13:15 (America/New_York) | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
ABSTRACT:
Throughout the COVID-19 pandemic, countries relied on a variety of ad-hoc border control protocols to allow for non-essential travel while safeguarding public health: from quarantining all travellers to restricting entry from select nations based on population-level epidemiological metrics such as cases, deaths or testing positivity rates. Here we report the design and performance of a reinforcement learning system, nicknamed ‘Eva’. In the summer of 2020, Eva was deployed across all Greek borders to limit the influx of asymptomatic travellers infected with SARS-CoV-2, and to inform border policies through real-time estimates of COVID-19 prevalence. In contrast to country-wide protocols, Eva allocated Greece’s limited testing resources based upon incoming travellers’ demographic information and testing results from previous travellers. By comparing Eva’s performance against modelled counterfactual scenarios, we show that Eva identified 1.85 times as many asymptomatic, infected travellers as random surveillance testing, with up to 2-4 times as many during peak travel, and 1.25-1.45 times as many asymptomatic, infected travellers as testing policies that only utilize epidemiological metrics. We demonstrate that this latter benefit arises, at least partially, because population-level epidemiological metrics had limited predictive value for the actual prevalence of SARS-CoV-2 among asymptomatic travellers and exhibited strong country-specific idiosyncrasies in the summer of 2020. Our results raise serious concerns on the effectiveness of country-agnostic internationally proposed border control policies that are based on population-level epidemiological metrics. Instead, our work represents a successful example of the potential of reinforcement learning and real-time data for safeguarding public health.
BIO:
Hamsa Bastani is an Assistant Professor of Operations, Information, and Decisions at the Wharton School, University of Pennsylvania. Her research focuses on developing novel machine learning algorithms for data-driven decision-making, with applications to healthcare operations and social good. Her work has received several recognitions, including the Wagner Prize for Excellence in Practice (2021), the Pierskalla Award for the best paper in healthcare (2016, 2019, 2021), the Behavioral OM Best Paper Award (2021), as well as first place in the George Nicholson and MSOM student paper competitions (2016).

Fall 2023 GRASP SFI: Jim Fan, NVIDIA AI, "Generalist Agents in Open-Ended Worlds"
2023-09-13 15:00 - 16:00 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
This is a hybrid event with in-person attendance in Levine 307 and virtual attendance on Zoom.
ABSTRACT
Autonomous agents have made great strides in specialist domains like Atari games and Go. However, they typically learn tabula rasa in isolated environments with limited objectives, thus failing to generalize across a wide spectrum of tasks and capabilities. Inspired by how humans continually learn and adapt in the open world, we advocate a trinity of ingredients for building generalist agents: 1) an environment that supports an infinite variety of tasks and goals, 2) a large-scale database of multimodal knowledge, and 3) a flexible and scalable agent architecture. We introduce MineDojo, a new framework built on the popular Minecraft game that features a simulation suite with 1000s of diverse open-ended tasks and an internet-scale knowledge base with YouTube videos, Wiki pages, and Reddit posts. We also propose two new algorithms on top of MineDojo: 1) MineCLIP, a foundation reward function reminiscent of RLHF for embodied agents; and 2) Voyager, an LLM-powered lifelong learning agent that explores and improves itself purely in-context. We look forward to seeing how MineDojo empowers the community to make more progress on the grand challenge of open-ended agent learning.

CBE Seminar: "Improving the Sustainability of Solvent-Borne Paints and Coatings through Fundamental Studies of Polymerization Reactions" (Soroush, Drexel University)
2023-09-13 15:30 - 16:30 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
The global market size of paints and coatings (P&C) was US$164 Billion in 2022 and is forecast to grow to US$241Billion by 2030. A fast-growing sector in the P&C industries is acrylics. P&C should contain a solvent in order to be brushable/sprayable. However, in the case of solvent-borne P&C, their improved sustainability requires decreasing their organic solvent contents. This sustainability-applicability tradeoff can be addressed by preparing P&C from polymers with lower average molecular weights, which can be produced via high-temperature (> 130 °C)free-radical polymerization. However, at these temperatures, several reactions — that are of little significance at low temperatures — strongly affect the polymer product quality. These so-called secondary reactions include monomer self-initiation, monomer-solvent and monomer-molecular oxygen co-initiation, depropagation, β-scission, and backbiting. We have made advances in quantum-level polymerization reaction modeling — that have enabled us to discover new reactions and fundamentally study previously known reactions in thermal polymerization of acrylates — as well as in macroscopic-scale mechanistic modeling and optimization of high-temperature polymerization reactors. Sample results from these studies will be presented. They will include new theoretical and experimental insights that can be used to produce more sustainable, higher-quality acrylic P&C at lower costs. The self-initiation of acrylates at high temperatures improves the polymer quality and reduces the operating costs due to less or no use of relatively expensive conventional initiators.

BE Doctoral Dissertation: "Batch effect detection and harmonization methods for quantitative features extracted from medical images" (Hannah Horng)
2023-09-15 10:00 - 12:00 | Class of 62 Auditorium, John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA, 19104
The Department of Bioengineering at the University of Pennsylvania along with Drs. Despina Kontos and Taki Shinohara proudly announce the Doctoral Dissertation Defense of Hannah Horng.

Title: Batch effect detection and harmonization methods for quantitative features extracted from medical images
Date: September 15, 2023
Time: 10:30am
Location: John Morgan Building – Class of ’62 Auditorium.

Zoom option:

https://upenn.zoom.us/j/98693898665?pwd=[REDACTED]
Meeting ID: 986 9389 8665
Passcode: [REDACTED]

The public is welcome to attend.

Fall 2023 GRASP Seminar: GRASP Research Overview - Day 2
2023-09-15 10:30 - 11:45 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
GRASP Lab faculty confirmed presentations (where appropriate their presenters)…
*This is a HYBRID Event with in-person attendance in Wu & Chen Auditorium and virtual attendance via Zoom.
Dr. Ani Hsieh (Welcome and Introduction)
Dr. Jean Gallier
Dr. Michelle Johnson (presented by Francis Sowande)
Dr. Vijay Kumar (presented by Jake Welde)
Dr. Lingjie Liu
Dr. Nik Matni (presented by Fengjun Yang)
Dr. George Pappas
Dr. Cynthia Sung
Dr. Marc Miskin

Engineering Faculty Teaching Forum: "Being Accessible to Students while Preserving Your Time"
2023-09-15 12:00 - 13:15 | Towne 108, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Finding time to support and mentor students can be challenging. Drs. Lee Bassett and Jennifer Lukes will start this informal conversation by sharing ideas for promoting positive relationships with students while maintaining boundaries to preserve our time. We will consider ways to use office hours efficiently, as well as ways to leverage technology to simplify scheduling and communication. Lunch will be provided for those who register in advance<https://ctl.upenn.edu/event/being-accessible-to-students-while-preserving-your-time/>.

PICS Colloquium: "The Virtual Pregnancy: Using Computational Models to Probe Human Reproduction"
2023-09-15 14:00 - 15:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Preterm birth affects approximately ten percent of pregnancies and rates of maternal mortality in the US are rising. Computational investigations of pregnancy have great potential to explore fundamental aspects of reproductive physiology that are otherwise difficult or even impossible to investigate in humans. There are few-to-no good animal models of human pregnancy, and the reasonable ethical restrictions on experimentation with pregnant women limit clinical research. This talk will discuss how image-based computational modeling techniques can be used across length-scales to study different aspects of human pregnancy. Examples considered will include (a) models of individual collagen fibrils in preterm fetal membrane rupture, (b) maternal-fetal oxygen transport in the placenta, and (c) stresses in C-section scars at risk of rupture in subsequent pregnancies. With the recent worldwide attention given to poor maternal and fetal outcomes, fundamental bioengineering research into the mechanisms of preterm birth is timely and necessary. Computational models—including even full ‘digital twin’ models of pregnant persons—present a unique opportunity to advance an under-studied branch of medicine with significant financial and societal implications.

MEAM Seminar: "Insect Respiratory Biomechanics and Insect-inspired Microfluidics"
2023-09-19 10:00 - 11:30 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Insect respiration is characterized by the rapid transport of respiratory gases within the organism and efficient exchange with the external environment. This unique system is comprised of a network of tracheal tubes that directly supply oxygen to the cells throughout the body, eliminating the need for blood as an intermediate oxygen carrier. The remarkable diversity of insects and their astonishing metabolic rates, the highest in the animal kingdom for flying insects, provide evidence of the success of their respiratory strategy. Microfluidic technology, particularly in the domains of gas microfluidics and tissue engineering, stands to benefit from emulating the mechanical proficiency demonstrated by insects in manipulating fluids at the microscale. Despite this significance, our understanding of the fundamental principles underlying insect respiration remains incomplete. In this talk, we will present mathematical, microfluidic, and computational modeling of insect respiration based on data from large, inactive and small, highly active insects, including the darkling beetle Zophobas morio and the fruit fly Drosophila melanogaster. Our results suggest that insect respiration is highly versatile with largely automated, distributed control mechanisms. Finally, we will present our work developing microfluidic infusion pumps based on principles of insect respiration. They are powered by the arterial pulse and have the potential to drastically reduce the profile of ambulatory infusion pumps for the delivery of insulin, chemotherapy, other therapeutics, and vaccines.

MEAM Ph.D. Thesis Defense: "Multi-Scale Probing of Colloidal Sedimentation Dynamics in Active Suspensions"
2023-09-20 09:00 - 10:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Microorganisms, although challenging to observe, are ubiquitous in both natural ecosystems and industries. They inhabit diverse environments: natural ones ranging from small river tributaries and lakes to oceans, as well as in industrial settings, like wastewater treatment plants and food manufacturing. In these diverse contexts, microorganisms coexist with settling particles, a process heavily influenced by gravity. Consequently, gravity significantly influences microorganisms’ behaviors, impacting aspects such as locomotion and nutrient uptake. The presence of microorganisms alongside colloidal particles, specifically, can influence industrial processes and transport properties. The comprehension of microorganisms’ physical and biological behaviors in aquatic environments, especially under external forces like gravity, remains elusive and challenging.
In this thesis, I explore the dynamics of spherical colloidal sedimentation in the presence of swimming Escherichia coli across various concentrations within the dilute regime. The sedimentation processes receive comprehensive characterization across length scales, through the examination of macro-scale settling speeds, meso-scale concentration profiles, and micro-scale particle diffusivities. First, I showcase how bacterial activity affects the concentration profiles of spherical particles—an alteration describable through an advection-diffusion equation with an added population dynamics term. Subsequently, I characterize the sedimentation speed of spherical particles across different bacterial concentrations, unveiling the emergence of two sedimentation fronts: particle- and bacteria-rich fronts. Even passive systems of poly-dispersed (by size) particles are known to show segregating sedimentation fronts; larger (and faster) settling particles will separate from smaller (and slower) ones, given enough time. In this context, heightened activity influences sedimentation speeds and the associated timescales tied to the appearance of the bacteria front. These timescales pertaining to the second front yield a phenomenological model that captures the sedimentation of passive particles within active fluids. Lastly, I explored the interactions between particles and bacteria in the presence of gravity, uncovering that bacterial-induced convective motions reduce the convective transport of colloidal particles. By increasing bacterial concentration, particle convection diminishes and nearly stabilizes. These observations reveal a correlation with measurements of macro-scale settling speeds. I demonstrate that the emergence of this phenomenon is associated with the development of complex bioconvection patterns. Overall, this dissertation illuminates the intricate interplay between microorganisms and particles in the presence of gravity, revealing nontrivial effects.

ASSET Seminar: "The Road to Explainable AI v2.0" (Eric Wong, Penn)
2023-09-20 12:00 - 13:15 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
ABSTRACT:
“A.I. has an explainability crisis”—Fortune Magazine. If you ask an ML researcher about explainability, you’ll find that there are a large number of interpretability methods with no clear consensus on what to use. In fact, it isn’t clear what many of these explanations even mean, let alone how they can be used. I will discuss a potential vision that moves beyond these limitations to the next generation of explainable AI: interpretations with provable guarantees and well-defined takeaways.
BIO:
Eric Wong is an Assistant Professor in the Department of Computer and Information Science at the University of Pennsylvania. He researches the foundations of robust systems, building on elements of machine learning and optimization to debug, understand, and develop reliable systems.

CBE Doctoral Dissertation Defense: "Molecular Mechanisms of Spatiotemporal Gene Control in Early Embryonic Development"
2023-09-20 12:00 - 13:30 | Towne 225
Development of a newly fertilized embryo is a dynamic, complex, and highly coordinated process that requires precise genetic regulation and control. As the embryo develops, DNA regulatory elements known as enhancers drive gene expression patterns in specific regions of an organism at a particular time. Mis-regulation of gene expression due to mutations in enhancers can result in severe disease phenotypes and developmental defects. However, understanding the fundamental mechanisms that activate and regulate precise transcription remains challenging. This thesis aims to elucidate the molecular mechanisms of enhancer-mediated transcriptional regulation in high spatiotemporal resolution in different genetic contexts.
Early development is largely controlled by maternally deposited proteins, while the zygotic genome remains transcriptionally silent. The transition from maternal to zygotic control has been extensively studied, yet we still lack a comprehensive understanding of the processes that result in zygotic genome activation. In Chapter 2, we identify distinct yet overlapping mechanisms of nuclear to cytoplasmic (N/C) ratio control on transcription driven by various enhancers under different genetic perturbations.
Enhancers contain unique binding sites for various proteins, known as transcription factors (TFs), that regulate spatiotemporal expression of a target gene. Many enhancers contain multiple binding sites for the same TF and the specific contribution of the various TF binding sites to the overall expression of a target gene is unclear. In Chapter 3, we characterize enhancer-mediated gene expression upon systematic modulation of TF binding sites. We find that mutating a single TF binding site results in a dramatic reduction in mRNA production. Through thermodynamic modeling, we uncover the synergistic capabilities of each binding site to the total transcriptional dynamics.
In this thesis we use a combination of live imaging, CRISPR/Cas9 genome editing technology, quantitative analysis, and mathematical modeling to explore a new world of gene regulation and transcriptional dynamics. By understanding the fundamental mechanisms that spatiotemporally control and modulate the expression of essential developmental genes, we can gain insights into gene mis-regulation and serious diseases.

Fall 2023 GRASP SFI: David Lentink, University of Groningen, "Avian Inspired Design"
2023-09-20 15:00 - 16:00 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
This is a hybrid event with in-person attendance in Levine 307 and virtual attendance on Zoom. This week’s speaker will be virtual.
ABSTRACT
My lab focusses on understanding every aspect of bird flight to improve flying robots—because birds fly further, longer, and more reliable in complex visual and wind environments. I use a multidisciplinary lens that integrates biomechanics, sensorimotor control and organismal & evolutionary biology with aerospace engineering, robotics and aerodynamics to advance our systems understanding of avian flight. The experimental approaches range from flying birds in custom-designed flight arenas, scanning their 3D shape at high-speed and unraveling their musculoskeletal control strategies to making innovative direct aerodynamic force measurements in flight. I will show how these and other ongoing studies in my lab have inspired new biohybrid soft morphing aerial robots that we design and fly in my lab.

CBE Seminar: "Facile Synthesis of Polymeric Nanomaterials via Chemical Vapor Deposition Techniques" (Yang, Cornell)
2023-09-20 15:30 - 16:30 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Polymer is often considered one of the most prevalent materials in the modern age. While it has been predominantly synthesized in solution and processed into a variety of macroscopic sizes and shapes, the need for programmability in materials’ microscopic properties has challenged the traditional synthesis approaches. Recent advances in vacuum-based synthesis technologies, such as the initiated Chemical Vapor Deposition (iCVD) and Condensed Droplet Polymerization (CDP), have enabled a new mode of control over material properties during polymerization. Distinct from prior research that has placed a strong emphasis on the design of monomer molecular structure and controlled polymerization, the all-dry synthesis enables manipulation of the molecular interactions, such as molecular complexing and nanoscale dewetting, to achieve programmable nanoscale structures. In this talk, I will use two examples to illustrate the underlying principles and potential benefits of this distinct synthesis paradigm: (i) enabling vapor-phase molecular complexation during polymerization to achieve an unprecedented range of molecular weight, mechanical properties, and film morphology; (ii) leveraging nanoscale dewetting of nonpolar liquids to create polymeric nanodomes with spatiotemporal resolution on the nanoscale. Taken together, these advances in manipulating the physicochemical interactions during polymerization are poised to open up a new dimension in the design and synthesis of programmable polymeric materials, benefiting numerous existing and future technologies, ranging from nano-optics to drug delivery.

MSE Seminar: "DumoLab Research: Regenerative Architecture with Biomaterials" Weitzman School of Design - University of Pennsylvania
2023-09-21 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Dr. Mogas-Soldevila will give an overview on her DumoLab research at the Weitzman School of Design at Penn. Her works focuses on regenerative material practices bridging science, engineering, and the arts. DumoLab builds scholarship for materials design critique, and translates biomedical materials used in implants, drug delivery, and tissue scaffolding, into robust materials for use in product and architectural design that nurture both humans and the planet. Interdisciplinary research areas push forward biomaterials science for non-medical applications, growth-like large-scale and ambient conditions manufacturing, and new testing protocols and aesthetics for bio-composites in consumer products and the built environment.

ESE PhD Thesis Defense: "Toward High-performance Simple Models of Legged Locomotion"
2023-09-21 15:00 - 16:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
This thesis addresses the challenges of model-based planning and control in legged locomotion, particularly the trade-off between computational speed and robot performance presented by different levels of model complexities. Full-order models, while rich in detail, are often too computationally demanding for real time planning, whereas conventional reduced-order models (ROMs) tend to oversimplify the dynamics, limiting overall performance potential. Our research focuses on a novel approach — the direct optimization of ROMs. This study seeks to enhance the performance of legged robots by automatically discovering the optimal ROMs that simultaneously deliver high robot performance while maintaining the necessary low dimensionality for real time planning applications. In the beginning of the thesis, we focus on a special case where we aim to find whole-body orientation coordinates (WBO) for legged robots that minimize angular momentum errors. This optimal WBO, while being a simple forward kinematic function, serves as a proxy of the real angular momentum and can be applied to complex tasks such as humanoid natural walking. In the second part of the thesis, we formulate a bilevel optimization problem to find optimal ROMs agnostic to controller choices, driven by user-defined objectives and task distributions. The results show substantial improvements in walking speed, ground slope adaptability and torque efficiency on a bipedal robot Cassie. Lastly, we cast the ROM optimization problem as a model-based reinforcement learning (RL) problem to further improve the model performance. This does not only show better performance improvements in experiment but also provides an easier way to implement model optimization and to realize the model performance on the robot.

BE Doctoral Dissertation Defense: "Pooled tagging of endogenous proteins for exploration of the human proteome driven by prime editing"
2023-09-21 15:00 - 17:00 | Colket Translational Research Building (Room 4040)
The Department of Bioengineering at the University of Pennsylvania and Dr. Ophir Shalem are pleased to announce the Doctoral Dissertation Defense of Henry Sanchez.

Title: Pooled tagging of endogenous proteins for exploration of the human proteome driven by prime editing
Date: September 21, 2023
Time: 3:00pm
Location: Colket Translational Research Building (Room 4040)

The public is welcome to attend.

BE Seminar: "Engineering the cell-matrix interface – understanding and guiding cell function" (Claudia Loebel, University of Michigan)
2023-09-21 15:30 - 16:30 | 216 Moore Building
The native extracellular microenvironment dynamically remodels as cells synthesize, assemble, and remodel their surroundings during tissue development, injury, and repair. In my research group, we use engineered systems to both probe mechanisms of cell-extracellular matrix (ECM) interactions (e.g., mechanobiology) and to guide cell function towards therapeutic behaviors (e.g., tissue repair/regeneration). In this seminar, I will share our recent efforts to visualize and identify the composition of secreted ECM to better understand cellular responses and to design programmable soft materials that harness dynamic cell-ECM interactions.
We have used these systems to reproduce folding morphologies of epithelial tissues (e.g., airway constriction), and to manipulate secreted ECM components as means to better understand the evolution of matrix in organ development (using lung organoids) and repair (using ex vivo lung tissue). Our evolving understanding of matrix dynamics and turnover will not only open up new avenues for understanding biological mechanisms but will also allow us to design better materials systems for therapeutic interventions.

PRECISE Seminar: Designing Computing Systems for Robotics and Physically Embodied Deployments
2023-09-22 10:00 - 11:00 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States

ESE Fall Seminar - "Tools for designing some exciting chips"
2023-09-22 11:00 - 12:00 | Berger Auditorium (Room 13), Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA, 19104, United States
There is an enormous interest in developing customized, domain-specific systems-on-a-chip. Continued improvement in computing efficiency requires functional specialization of hardware designs. But designing complex chips is difficult. This talk presents the Chipyard framework, an integrated SoC design, simulation, and implementation environment for specialized compute systems. Chipyard includes configurable, composable, open-source, generator-based IP blocks that can be used across multiple stages of the hardware development flow while maintaining design intent and integration consistency. We discuss some sample designs, the use of the framework in classes, and opportunities for extension and improvement.

CBE Seminar: "Design of Solid-state Nanomaterials for Electrocatalysis: A Case Study of Oxygen Evolution Reaction Electrocatalysts" (Yang, UIUC)
2023-09-25 15:30 - 16:30 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
High-level control of atomic and surface structures is a hallmark of the application of nanomaterials in a range of electrochemical and electrocatalytic devices, such as water electrolyzer. They play critical roles in our effort to develop energy conversion and storage technologies that have net zero carbon impacts. Nanostructured metal oxides made for catalyzing the oxygen evolution reaction (OER) is one representative example. Unlike the traditional heterogeneous catalysis, both bulk and surface properties are important in the design of active and durable electrocatalysts. This is because besides the adsorbate evolution mechanism (AEM), lattice oxygen mechanism (LOM) is often involved in the catalytic cycle. In this talk, I will present our recent work on the synthesis-structure-electrocatalytic property relationship of complex oxides that can be described in a generic formula of AxByOz, where A and B can be a single metal cation or mixed cations located at a given lattice site. We haveexamined several archetypes of oxide structures, including perovskite, pyrochlore, spinel, and Ruddlesden-Popper (RP) phasecompounds and their site-mixed solids, all of which are found to be active for OER under either acid or base conditions. Ourresults indicate defect engineering in these solids is particularly important for OER catalysis. Thus, it is essential, besides agood understanding of heterogeneous catalysis, one needs to take a solid state chemistry view in order to uncovering thecatalyst design for optimal performance. How to regulate the cation sites and oxygen defect chemistry for enhancing the bondand lattice stability of key structural constituents can be important. The new understandings should inform the approach tothe fabrication of earth-abundant oxide electrocatalysts for hydrogen production and utilization.

LSRM Presents The Robert Maddin Lecture in Materials Science: "Active & Adaptive Matter Driving Cell Dynamics"
2023-09-25 16:00 - 17:30 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Control of shape and movement is essential for cell physiology, from cell migration to control of tissue shape. The mechanical behaviors of living cells are controlled by materials constructed by protein-based assemblies within the cell interior. These soft materials both regulate how forces generated by individual mechanoenzymes are transmitted to cell and tissue scales as well as how mechanical properties evolve, or adapt, over time to allow for smooth transitions. I will describe my lab’s recent efforts to understand the design principles of the active, soft materials that drive multi-cellular dynamics. In particular, I will describe our progress to reveal design principles by which the actin cytoskeleton senses, generates, and adapts to mechanical force. Hopefully, I will convince you that the materials within cells provide a rich playground to understand design principles of active and adaptive soft materials.

MEAM Seminar: "Defending the Planet: The DART Mission, and Mechanics Among the Asteroids"
2023-09-26 10:00 - 11:30 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
An on-orbit demonstration of asteroid deflection is a key test of our ability to defend the planet from an incoming asteroid. The recent DART (Double Asteroid Redirection Test) mission was NASA’s demonstration of kinetic impactor technology, impacting an asteroid to adjust its speed and path. The DART spacecraft impacted the asteroid Dimorphos on September 26, 2022, and was the first-ever space mission to demonstrate asteroid deflection by a kinetic impactor. We discuss the mission, and the critical role that mechanics plays in such planetary defense missions.
Most asteroids are “small” rocky bodies (they can vary in size from sub-m to several hundred km). The structure and surface topography of asteroids are determined by impact and fracture processes that occur over an immense range of timescales. Recent observations have demonstrated that many small asteroids are “rubble-piles,” collections of rocks held together by gravity. What determines this structure? We examine the disruption and breakdown of asteroids by studying the multiscale mechanics of dynamic fracture and fragmentation, coupled with computational simulations of gravitational re-accumulation. The critical mechanisms are addressed through fundamental high-strain-rate experiments, high-speed visualization, theoretical and computational modeling of failure processes, and computational simulations of asteroid damage and disruption. Our focus is on the relative roles of impact and thermal loading on the nature of near-Earth asteroids (NEAs) that may potentially impact the Earth.

ESE Fall Seminar - "Large Observational Study of the Causal Effects of a Nudge and the Geometry of Causality"
2023-09-26 11:00 - 12:00 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Nudges are interventions promoting healthy behavior without forbidding options or significant incentives. As an example of a nudge, the Apple Watch encourages users to stand by delivering a notification if they have been sitting for the first 50 minutes of an hour.
Based on 76 billion minutes of observational standing data from 160,000 subjects in the public Apple Heart and Movement Study, amount of data in the field that makes this work one of the largest ever in the subject, we estimate the causal effect of this notification using a novel regression discontinuity design for time-series data with time-varying treatment. We show that the nudge increases the probability of standing by up to 44%, a very significant effect compared to what has been reported in the literature, remaining effective with time, even after almost 2 years. The nudge’s effectiveness increases with age, and it is independent of gender. Closing Apple Watch Activity Rings, a visualization of participants’ daily progress in Move, Exercise, and Stand, further increases the nudge’s impact. We conclude the presentation with some recent work on connections between geometry and causal inference.
The first part of the presentation is joint work with Achille Nazaret while the second is with Amir Farzam and Allen Tannenbaum.

ESE PhD Thesis Defense: "Control of Multi-Contact Systems via Local Hybrid Models"
2023-09-26 13:00 - 15:00 | Room 35, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
For many important tasks such as manipulation and locomotion, robots need to make and break contact with their environment. Although such multi-contact systems are common, they pose a significant challenge when it comes to analysis and control. This thesis exploits the local hybrid structure of such problems and presents scalable and fast algorithmic solutions. First, we present an MPC framework for multi-contact systems. The method is based on the alternating direction method of multipliers (ADMM) and is capable of high-speed reasoning over potential contact events. Then, we focus on utilizing tactile measurements for reactive control, which is very natural yet underexplored in the robotics community. We propose a control framework to design provably stabilizing tactile feedback policies by exploiting the local complementarity structure of contact dynamics. Lastly, inspired by the connection between rectified linear unit (ReLU) activation functions and linear complementarity problems, we present a method to analyze stability of multi-contact systems in feedback with ReLU network controllers.

Fall 2023 GRASP Seminar: Paul Debevec, Eyeline Studios Powered by Netflix, “From Virtual Cinematographhy to Virtual Production”
2023-09-26 14:00 - 15:00 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
*This seminar will be held in-person in Levine 307 as well as virtually via Zoom. The seminar will NOT be recorded.
ABSTRACT
This talk will describe how virtual cinematography techniques developed at UC Berkeley for image-based modeling, rendering, and lighting helped enable iconic visual effects sequences in movies such as The Matrix, X-Men, Spider-Man 2, Benjamin Button, and Avatar. It will also show how real-world image-based lighting techniques which surround actors with computer-controlled LED’s have led to new virtual production techniques seen in The Social Network, Gravity, Rogue One, Asura, and The Mandalorian. The talk will conclude by describing new research to improve the lighting reproduction, color rendition, and alpha compositing capabilities of these new virtual production stages.

ASSET Seminar: "Safety through Agility - Safe and Performant Control for Learning-Enabled Autonomous Systems" (Mangharam, Penn)
2023-09-27 12:00 - 13:15 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
ABSTRACT:
We present three approaches to combine formal methods, control theory, and machine learning for safe and performant autonomous systems.

Safe control for learning-enabled systems: We present our recent progress on how to learn safe adaptive behavior for highly interactive multi-agent systems. We will introduce how to quantify the uncertainty of closed-loop control systems using a frequentist method called conformal prediction and incorporate the uncertainty for safe perception-based control.
Learning Introspective Control: Oftentimes the systems that we control operate under different conditions due to changing environments, varying system parameters or changes in payload. As such, we strive to develop computationally efficient, data-driven system models that allow predictive controllers to adapt to changes in the environment in real-time. We focus on using Gaussian Processes as models to study the problem in the context of driving on surfaces with changing friction coefficients.
Differentiable Predictive Control: Finally, we discuss the application of differentiable predictive control for large-scale urban road networks.

Fall 2023 GRASP SFI: Robert Baines, ETH Zürich, "Material system design for predictable shape-morphing robots"
2023-09-27 15:00 - 16:00 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
This is a hybrid event with in-person attendance in Levine 307 and virtual attendance on Zoom. This week’s speaker will be virtual.
ABSTRACT
Robots are traditionally designed with immutable physical hardware and control policies that make them specialized for repetitive, structured tasks and environments. This talk presents work toward robots that actively change shape to accomplish a variety of tasks in diverse environments. Shape-changing robots are pursued at two levels. First, I will discuss the design and modeling of shape-morphing components, including variable stiffness materials and variable-trajectory soft actuators. Component-level analysis leads to insight into how actively tunable stiffness differentials can yield myriad deformations. Inverse models that recapitulate shape-morphing components’ highly nonlinear geometric and material behavior allow for systematic mechanical programming of shape-morphing robotic function. These foundational studies inform the second part of the talk, in which I will discuss how shape-morphing components are applied to create an adaptive amphibious quadruped robot. Harnessing active stiffness-tuning materials, the robot features limbs that switch between programmed shapes for effective propulsion in multiple environments. The robot testifies to the efficacy of “adaptive morphogenesis,” a design strategy that leverages shape-morphing and gait adaptability to improve performance across multiple environments.

MSE David P. Pope Distinguished Lecture: "Light, Materials and Interfaces: The Complex Dance That Allows CLIP-based 3D Printing," Stanford University
2023-09-28 11:00 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract
The production of polymer products relies largely on age-old molding techniques. A major reason for this is that additive methods have not delivered meaningful alternatives to traditional processes—until now. In this talk, I will describe Continuous Liquid Interface Production (CLIP) technology, which embodies a convergence of advances in software, hardware, and materials to bring the digital revolution to polymer additive manufacturing. CLIP uses software-controlled chemistry to produce commercial quality parts rapidly and at scale by capitalizing on the principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between a forming part and a printer’s exposure window. Instead of printing layer-by-layer, this allows layerless parts to ‘grow’ from a pool of resin, formed by light. Compatible with a wide range of polymers, CLIP opens major opportunities for innovative products across diverse industries. Previously unmakeable products are already manufactured at scale with CLIP, including the large-scale production of running shoes by Adidas (Futurecraft 4D); mass-customized football helmets by Riddell; the world’s first FDA-approved 3D printed dentures; and numerous parts in automotive, consumer electronics, and medicine. At Stanford, we are pursuing new advances including digital therapeutic devices in pediatric medicine, new multi-materials printing approaches, recyclable materials, and the design of a high-resolution printer to advance technologies in the microelectronics and drug/vaccine delivery areas, including novel microneedle designs as a potent vaccine delivery platform.

MEAM Ph.D. Thesis Defense: "A Study of Hydrogel Mechanics with Application on the Fracture of Human Blood Clots"
2023-09-29 10:00 - 11:00 | DRLB A6, 209 S. 33rd Street, Philadelphia, PA, 19104, United States
Loading of biological and synthetic hydrogels involves large deformations, and there exists a large literature devoted to their experimental characterization. Analytical investigations have recognized the importance of contributions originating from the liquid phase, and experiments have verified them. The liquid flux fields in these materials usually exhibit fully three-dimensional profiles and are time-dependent. This coupled mechanical-diffusional poroelastic problem is studied here within the framework of continuum poro-elasticity and presents an abundance of interesting phenomena. One such interesting observation in many experiments is the tendency of some hydrogel materials to expel liquid under tension. This behavior is well-documented in biologically swollen tissues, but it appears to be absent from a majority of synthetic hydrogels which exhibit the more common behavior of absorbing liquid under tension. In this thesis the poro-elastic fracture of hydrogel materials is studied and the energy release rate, a fundamental quantity of fracture mechanics, is computed. Liquid flow is shown to contribute significantly to fracture, and it can be utilized to design tough hydrogels.
Beyond the theoretical investigations, continuum poroelasticity is applied to the fracture behavior of human blood clots whose main component is a fibrin gel. Fibrin is a blood clotting protein and the main structural components of clots and thrombi. Different fibrin(ogen) concentrations, types of loading (tension and shear), and geometries are used to study the dependencies of the toughness on the fibrin(ogen), showing that fracture toughness increases with fibrin(ogen) concentration. The poroelastic constitutive model used, incorporating the intricate fibrin fiber mechanics, captures well the experimental data. Insights for the microstructural process happening during fracture are provided through a combination of finite element results and microscopy imaging.

PRECISE Seminar: Network Intelligence Role in Future Mobility
2023-09-29 10:00 - 11:00 | Levine 307, 3330 Walnut Street, Philadelphia, PA, 19104, United States
