Penn Engineering Events

CBE Seminar: "Complexity in the Chemistry and Physics of Lipid Membranes as a Handle to Activate the Delivery of Cargo to Cells”
2019-09-11 15:00 - 16:00 (America/New_York) | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Lipid materials having nanostructures that deviate from the conventional flat bilayer arrangement such as hexagonally packed lipid tubes and bi-continuous cubic phases are ubiquitous in nature. Their role remains elusive but over the years several pathologies and organelle functions have been coupled to lipid membrane structural complexity. In this talk, we will discuss lipid membrane polymorphism and how it can be exploited to generate a new class of materials for the delivery of cargo to cells. We combine a number of techniques including X-ray scattering, cryo-EM, and cell culture to demonstrate that the structure of lipid nanoparticles is a powerful handle to boost the delivery of genes to cells. The simple argument that non-lamellar phases having intertwined nanoscale channels exist to increase surface-to-volume ratio might be insufficient to completely describe the experimental findings.
If there is time, we will also introduce the concept of soft-material alloys. Lipids and polymers can mix in hybrid membranes having synergistic dynamical and structural properties; many of which are seen in lipid-protein membrane systems in nature

MEAM Seminar: "Dynamical Systems Approach to Geophysical and Aerospace Flows"
2019-09-10 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
A dynamical systems approach is taken to explain the dynamics of two classes of ‘gap-leaping’ geophysical flow as well as the hypersonic second-mode instability. First, in the context of a loop current system, it is shown that multiple steady flow patterns with hysteresis exist and appear to satisfy a cusp catastrophe geometry of solutions. Which state the system assumes (looping or leaping or periodic eddy shedding) and when transitions between states occur, will be discussed in terms of fundamental vorticity advection and dissipation. Second, a global perspective of Gulf of Maine circulation leads to a new mechanism for Scotian Shelf Water crossover events. Finally, by considering an idealized system and an analogy with harmonic oscillators, a fundamental mechanism for the hypersonic second-mode instability is proposed.

MSE Thesis Defense: “High Loading Oxide Anodes for Lithium Ion Batteries via a Superelastic Graphene Composite Approach”
2019-09-09 14:30 - 15:30 | LRSM 325, 3231 Walnut St., Philadelphia, PA, 19104

MSE Lab Safety Seminar
2019-09-05 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States

"Compressive Sensing: From Algorithms to Circuits"
2019-09-05 10:30 - 11:30 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Compressive Sensing is an acquisition technique which relies on the sparsity of the underlying signals, to enable sampling below the classical Nyquist rate. To do so, the signals must be acquired in an incoherent way with respect to the sparsity basis, which is classically obtained in practice by acquiring the signal through projection on a random PAM signal with i.i.d. symbols.
We first show that advantages with respect to the above “classical” compressive sensing approach can be achieved by exploiting the fact that, while sparsity is not under a system designer’s control, incoherence is, and therefore flexibility and creativity in implementing compressed sensing systems rely on the strategic design and control of incoherence. To accomplish this, we then assume that the signals to be acquired are not only sparse, but also localized, e.g. for nearly all practical applications, the signals of interest preferentially occupy a given subspace (for instance they are all low-pass or high-pass in the frequency domain). We show how, for localized signals, the acquisition sequences can be designed to maximize their “rakeness,” that is, to maximize their capability to collect the energy of the samples during the acquisition phase and increase by several dBs the average SNR achieved in signal reconstruction.
We will then describe the design in a 0.18um CMOS technology of the most popular architecture for implementing A/D converters based on compressive sensing, namely the Random Modulation Pre-Integration (RMPI). We will show that the direct circuit implementation of the classical acquisition scheme exploiting i.i.d sequences leads to a highly suboptimal solution, and one needs therefore to follow a synergetic design between algorithm-circuit-system. We will show how the use of rakeness-based CS acquisition sequences can reduce the complexity of the implemented A/D from 16 to 8 stages for processing ECG signals and from 64 to 24 for EMG ones. Furthermore, rakeness-derived sequences also eliminate the necessity for pre- or post-acquisition filtering stages intended to suppress high frequency artifacts and 60-Hz power-line noise interference.
Finally, we will show how the use of CS guarantee some level of privacy in information transmission, which makes the CS signal acquisition paradigm even more suitable for applications in the area of Body Area Networks and Internet of Things.

CBE Seminar: "Embryogenesis: A Cascade of Dynamical Systems"
2019-09-04 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
We aim to establish and experimentally test mathematical models of embryogenesis. While the foundation of this research is based on models of isolated developmental events, the ultimate challenge is to formulate and understand dynamical systems encompassing multiple stages of development and multiple levels of regulation. These range from specific chemical reactions in single cells to coordinated dynamics of multiple cells during morphogenesis. Examples of our dynamical systems models of embryogenesis – from the events in the Drosophila egg to the early stages of gastrulation – will be presented. Each of these will demonstrate what had been learned from model analysis and model-driven experiments, and what further research directions are guided by these models.

Penn Engineering Connects: A Reception on Inclusion
2019-09-03 16:30 - 17:30 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
A reception on inclusion will be held for new Penn Engineering doctoral students to connect them to their peers and supporting structures within the school.
Please join the Dean, Deputy Dean, the Director of the Office of Diversity and Inclusion, faculty and staff leaders including chairs, graduate group chairs and coordinators, and leaders of student groups.
All are welcome. Refreshments will be served.

MEAM/LRSM Seminar: "Enabling Soft, Flexible 2D Materials and Sensors"
2019-08-30 15:30 - 16:30 | Reading Room, LRSM, 3231 Walnut Street, Philadelphia, PA, 19104, United States
Low temperature synthesis of high quality 2D materials directly on flexible substrates remains a fundamental limitation towards realization of robust, strainable electronics possessing the unique physical properties of atomically thin structures. Here, we describe room temperature synthesis of uniform, stoichiometric amorphous MoS2, WSe2, and other transition metal dichalcogenides and subsequent large area (>5 cm2) photonic crystallization to enable direct fabrication of devices based on two-dimensional materials on large area flexible or rigid substrates. Fundamentals of crystallization kinetics for different monolithic and heterostructured TMDs are examined to apply this new synthesis approach for affordable, wearable devices. Example devices include photodetectors with photocurrent output and response times comparable to those fabricated via CVD and exfoliated materials on rigid substrates and the performance is unaffected by strains exceeding 5%. Flexible molecular sensors fabricated in this way detect diverse vapor phase substances with sub-ppm sensitivity. Functionalization of laser-written 2D TMD sensor transducers is also demonstrated for healthcare applications. Devices and circuits directly written from photonically annealed monolithic TMDs thin films deposited on large area flexible substrates, with no photolithography or patterning, are also presented. Additionally, other advanced processing strategies that enable flexible 2D materials will be discussed, including h-BN van der Waals liftoff of GaN HEMT devices for future strainable RF devices.

CBE Doctoral Dissertation Defense: "Anisotropy and Aggregation in Self-Assembled Polymer Nanocomposites"
2019-08-30 14:00 - 16:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Committee: Robert Riggleman, PhD (co-advisor); Russell Composto, PhD (co-advisor); Ravi Radhakrishan, PhD; and Jeff Meth, PhD

MEAM Seminar: "Small, Autonomous, Flying Robots that can Feel and Map their Environment"
2019-08-27 14:30 - 15:30 | Room 307, Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Autonomous flight through unknown environments in the presence of obstacles is a challenging problem for micro aerial vehicles (MAVs). A majority of the current state-of-art research focuses on modeling obstacles as opaque objects that can be easily sensed by optical sensors such as cameras or LiDARs. Since obstacles may not always be opaque, particularly in indoor environments with glass walls and windows, robots (like birds) have a difficult time navigating to the unknown environments.
In this thesis, we describe the design, modeling, control and sensing for a new class of micro aerial vehicles that can navigate unknown environments and are robust to collisions. In particular, we present the design of the Tiercel MAV: a small, agile, light weight, collision-resistant robot powered by a cellphone grade CPU. The Tiercel is able to localize using a visual-inertial odometry (VIO) algorithm running on board the robot with a single downward facing wide angle camera. Next, we characterize the effects of impacts and collisions on the visual-inertial odometry running on board the robot. We further develop the system architecture and components to enable the Tiercel to fly autonomously in an unknown space, detect collisions using its on board IMU, and leverage that information to build a 2D map of the environment. Finally, we demonstrate the capability of a swarm of three Tiercel robots to navigate autonomously through an unknown, obstacle ridden space while sustaining collisions with the environment. Finally, our approach exploits contact to infer the presence of transparent or reflective obstacles like glass walls, allowing us to naturally integrate touch with visual perception for SLAM.

MEAM Seminar: "Nano-compatible Neuromorphic Computers: An All-passive Approach to Neural Networks"
2019-08-20 10:30 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
This era of the internet of things is poised to experience explosive growth in the number of interconnected smart electronic devices. Machine learning algorithms, such as neural networks, are expected to play an indispensable role in analyzing the data gathered by these devices, and in many cases, will also facilitate informed device responses. However, the prospect of connecting a billion devices to the cloud and implementing large-scale neural networks remotely is infeasible for applications such as autonomous driving, implantable medical devices, and robotic platforms, that need the information to be processed speedily, at a small power budget. To deliver these requirements, it becomes necessary to equip devices with hardware that is optimized for neural network computations. For nanoscale implementations of such “neuromorphic” computers, it is important to develop simple designs of constituent circuits so that the required architectural complexity can be achieved within the nanofabrication constraints.
Current “neuromorphic” hardware designs typically utilize active circuits, comprising of three-terminal devices, to implement artificial neurons, an approach that is not suitable for compact nanoscale implementations. In this talk, we will show, how all-passive circuits for artificial neurons, comprising of two-terminal devices only, can instead address these drawbacks effectively. We will introduce simple circuit representations of artificial synapses and discuss how these enable improved memory-efficiencies vis – a – vis contemporary designs. By combining the passive neurons and synapses in network configurations, we will demonstrate how all-passive neuromorphic computers can perform complex pattern recognition tasks, such as identifying numerical digits from their images, with accuracies greater than 95%. The classification accuracies, power consumption and areal footprint of all – passive neuromorphic computers will be compared to those of the state – of – the – art technology. On the fabrication front, we will introduce simple methods for realizing re-programmable and once-programmable artificial synapses and delve into their operational attributes. Simple electrochemical deposition techniques for fabricating neurons will also be presented. The results of this work will promote new approaches to the design and fabrication of integrated nanoscale neuromorphic computers.

CBE Doctoral Thesis Defense: "Utilization of Mems Techniques for the Fabrication of Scalable Energy Storage Devices"
2019-08-16 10:00 - 12:00 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Committee: Sue Ann Bidstrup Allen, Advisor; Raymond Gorte, John Vohs and Mark Allen

CBE Doctoral Dissertation Defense: "Utilization of MEMS Techniques for the Fabrication of Scalable Energy Storage Devices"
2019-08-16 10:00 - 11:30 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Committee Members: Sue Ann Bidstrup Allen, Advisor; Raymond Gorte, John Vohs and Mark Allen.

MEAM Seminar: “Delivering Expressive and Personalized Fingertip Haptic Cues”
2019-08-15 10:30 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
The importance of meaningful tactile experiences has become increasingly apparent in areas such as teleoperation, education, and gaming. As the applications of rendering haptic stimuli are growing, so are the requirements of haptic interfaces, in that the intended audience is becoming more diverse and the intended interactions are becoming more complicated. For the past few decades there has been a consistent effort to improve the range and realism of haptic cues, yet typical haptic rendering continues to be one-size-fits-all and low-dimensional. To render increasingly realistic haptic cues, we must focus on both expressiveness and personalization.
In this talk I will present work towards delivering more expressive and personalized fingertip haptic cues from the perspective of both mechanical design and rendering approach. I will first present the Fuppeteer, a parallel continuum manipulator that can move a flat surface around the fingertip with six degrees of freedom. This wearable device can provide combinations of normal and shear forces across the user’s entire fingertip, regardless of finger shape and size. We have evaluated system performance through force measurements and through a human-subject study. This talk will also feature ongoing development of algorithms for delivering personalized sensed cues, independent of the specific haptic device and remote sensor used. I will discuss both geometric and data-driven approaches, and I will provide preliminary measurements of the rendering error generated by each method.

MEAM Doctoral Dissertation Defense: "Additive Manufacturing and Mechanical Properties of Cellulose Nanofibril Materials"
2019-08-14 10:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Cellulose nanofibrils (CNFs) are a nanomaterial derived from plants that have high specific stiffness and strength, can be made into optically transparent materials, and are biodegradable. These properties make CNFs an attractive building block for bulk structural materials. However, CNFs are typically produced in aqueous suspension at low CNF weight fractions (<1 wt.%), which makes manufacturing bulk CNF materials challenging due to long processing times and the development of significant residual stresses during drying. As a result, applications of CNFs in structural materials are currently limited to thin films and their use as low concentration reinforcement in composite materials. The objective of this dissertation is to overcome current limitations in building neat CNF materials by using additive manufacturing approaches to print films from aqueous CNF solutions with controlled fiber orientation and to build bulk structures with mm-scale thicknesses and enhanced mechanical properties.
This dissertation reports the use of two additive manufacturing techniques, direct ink writing and laminated object manufacturing, to fabricate neat CNF thin films with controlled orientation and materials with millimeter-scale dimensions, respectively. The orientation of the CNFs in the printed films and the mechanical properties of the films and laminated CNF materials were experimentally characterized. Orientation in the printed CNF films was found to be controlled by the drying mechanics, and a correlation between orientation and stiffness was observed. The multi-ply CNF films and laminated bulk beams with thicknesses of up to 0.6 mm were found to have comparable stiffness and strength and increased toughness compared to single-layer CNF films. Key contributions of this dissertation include the development of a printing process to decrease the time to fabricate CNF films, a demonstration and a mechanics-based understanding of the control of fiber orientation in printed CNF materials, and a new process to realize bulk neat CNF materials with increased thickness and enhanced toughness.

MEAM Seminar: "Mechanical Models for DNA"
2019-08-13 10:30 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
We will discuss two complementary mechanical models for DNA that deal with, respectively two problems: one, phase transitions in a DNA molecule, and two, allosteric interactions between two ligands bound to DNA.
Experimental studies on single molecules of DNA have reported a rich variety of cooperative structural transitions, including coexistence of three phases, when a torsionally constrained DNA molecule is pulled using magnetic or optical tweezers. Our objective is to examine the aforementioned structural transitions using ideas from statistical mechanics and the theory of elasticity. We use foundational concepts from the Zimm-Bragg helix-coil transition theory and merge them with ideas from the theory of fluctuating elastic rods to model the mechanics of DNA. Furthermore, we use Poisson-Boltzmann to account for the electrostatic interactions between the ions and the negatively charged phosphate backbone of DNA. Using our model, we calculate the force and torque corresponding to the over-stretching transition characterized by a 70% jump in the contour length of the molecule and examine the effect of salt concentration on this transition.
In the next part, we present a mechanical model for computing the allosteric interaction energy between two ligands on DNA. This interaction is quantified by measuring the change in free energy as a function of the distance between the binding sites for two ligands. We show that trends in the interaction energy of two ligands binding to DNA can be explained using an elastic birod model which accounts for the elastic deformation of strands and base-pairs as well as the change in stacking energy due to perturbations in position and orientation of the bases caused by the binding of ligands. The strain fields produced by the ligands decay with distance from the binding site. The interaction energy of two ligands decays exponentially with the distance between them and oscillates with the periodicity of the double helix in quantitative agreement with experimental measurements. The trend in the computed interaction energy is similar to that in the perturbation of groove width produced by the binding of a single ligand which is consistent with molecular simulations. Our analysis provides a new framework to understand allosteric interactions in DNA and can be extended to other rod-like macromolecules whose elasticity plays a role in biological functions.
The results from our model are in agreement with multiple experiments documented in the literature and they generate new falsifiable predictions that can be experimentally tested.

BE Doctoral Dissertation Defense: "Multi-scale Brain Responses in the Development of Persistent Osteoarthritic Temporomandibular Pain"
2019-08-08 12:00 - 14:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
The Department of Bioengineering at the University of Pennsylvania and Drs. Eric Granquist and Beth Winkelstein are pleased to announce the Doctoral Dissertation Defense of Megan Sperry. The public is welcome to attend.

BE Doctoral Dissertation Defense: "Informing Neuromodulation Therapies with a Control-Theory Approach to Brain Network Plasticity"
2019-08-07 13:00 - 15:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
The Department of Bioengineering at the University of Pennsylvania and Dr. Dani Bassett are pleased to announce the Doctoral Dissertation Defense of Andrew Murphy.
The public is welcome to attend.

MEAM Seminar: "From Elder Care Service Robots to the Design of Low-Cost End-Effectors and Novel Manipulation Techniques"
2019-08-06 10:30 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Older adults are forming a much larger percentage of the population leading to a strain in the healthcare sector. It is expected that the population aged 65 and over in the United States alone will double in the next 30 years, and similarly worldwide. Despite abundance of the facilities to accommodate the growing older adult population, there is a shortage of caregivers to staff these facilities. With the scarcity of care options available, low-cost robots may be a creative and vastly accessible solution for simple mobile and manipulation tasks that would normally be handled by a caregiver.
This work proposes an investigation on both behavioral and technical aspects of human robot interaction in elder care settings, in view of a low-cost platform capable of executing desired tasks. The behavioral investigation combines a qualitative study with focus groups and surveys from not only the elders’ standpoint, but also from the standpoint of healthcare professionals to investigate suitable tasks to be accomplished by a service robot in such environment. Through multiple deployments of the robot at actual elder care facilities (such as at a low-income Supportive Apartment Living, SAL) and interaction with older adults, design guidelines are developed to improve on both interaction and usability aspects. The technical investigation proposes novel manipulation techniques and end-effector design focusing on minimizing hardware usage and cost, in addition to comply with safety constraints imposed by elder care facilities. Object picking through in-hand manipulation using custom-made end-effectors with no internal mobility (or zero degrees-of-freedom, DOF) is proposed. The resulting operation incorporates tipping and regrasping as in-hand manipulation operations. The lack of mobility is advantageous as no active forces can be applied directly to the object by the end-effector, and so the manipulated item be safely placed or removed by humans interacting with the robot, a desirable feature for manipulation tasks especially in elder care settings.

MEAM Seminar: "Microscale Robotic Wetware for Synthetic Biology"
2019-07-23 10:30 - 12:00 | Moore 216, 200 S. 33rd Street, Philadelphia, PA, 19104, United States
Small-scale robotic systems have emerged as promising tools to perform a wide-range of tasks in microbiology and medicine such as targeted delivery, cell manipulation, environmental monitoring, and microassembly. In order to perform these tasks, the robot must execute precise locomotion, take measurements from its environment, and use those measurements to make decisions. However, unlike their macroscale counterparts, microrobots typically lack intelligence on-board and are composed of simple microstructures which are driven using off-board hardware and software. Thus, small-scale actuators, sensors, computation, and communication modules are needed in order to develop intelligent, fully functional microrobots.
Concurrently with the field of microrobotics, synthetic biology has developed tools to design microorganisms to exhibit desired behaviors (e.g. sensing, communication, and decision-making). This talk will highlight a new paradigm for microrobot design and fabrication. Our approach uniquely hinges on biofabrication, or making things from living things, in order to create programmable biohybrid robots composed of both biological and synthetic materials. We design robot architectures that enable interfaces between biological cells and hardware giving rise to robots composed of living material, or robotic wetware. In particular, we will discuss our development of magnetically actuated soft micro bio robots (SMBRs) composed of natural hydrogels, which encapsulate and transport programmable living cells, while supporting cell growth and function on-board. By encapsulating cells, SMBRs can serve as individual cellular culture payloads or biofoundries in which cells, DNA vectors, and cellular byproducts are manufactured on-board and delivered to the environment. These results establish multi-functional robots that can be used as delivery vehicles for medical therapies, assistants for microbiological experiments, or building blocks for smart materials.

CBE Doctoral Dissertation Defense: "Polymer Infiltration Under Extreme Confinement"
2019-07-16 14:00 - 16:00 | Greenberg Lounge (Room 114), Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA, 19104, United States
Committee: Daeyeon Lee and Robert A. Riggleman, Co-advisors; Ravi Radhakrishnan and Zahra Fakhraai

MEAM Seminar: "A Multi-Scale Homogenization Model for the Viscoplastic Response of Polar and Sea Ice"
2019-07-16 10:30 - 12:00 | Moore 216, 200 S. 33rd Street, Philadelphia, PA, 19104, United States
The rheology of polar ice evolves in response to weather and climate changes, by modifying its microstructure. While the experimental evidence for the dependence of rheological properties on the microstructure is well documented, there are only a few modeling efforts to capture the rheological behavior of polar ice, mostly by fitting continuum models to the existing experimental data. However, for the rapidly changing polar and sea ice, we need a predictive model to forecast the behavior of polar ice in the future, for which we might not have any experimental data. In this work, we put forth a multi-scale homogenization model for the viscoplastic response of polar and sea ice, by incorporating important microstructural features.
In the Arctic, sea water freezes to form a layer of sea ice, a multi-phase composite, up to a few meters thick, with a complex microstructure spanning several length scales. At the smaller length scales, sea ice is a porous polycrystal with columnar grains, with brine-air inclusions embedded inside the grains or dispersed along the grain boundaries. This work presents a multi-scale constitutive response for sea ice by idealizing it as a three-scale composite where the brine-air inclusions are embedded inside a polycrystalline matrix composed of columnar grains. The results from our model match with published experimental data, by, most importantly, capturing the compressibility effects of brine-air inclusions.
In Antarctica ice sheets with a typical thickness of 1-3km, as the snow accumulates on the surface of the ice sheet, the snow beneath the top layer is densified and is eventually transformed into the ice with trapped air bubbles—bubbly ice. The size, shape and volume fraction of these air bubbles have a profound impact on the rheological response of the ice. In addition, bubble shape could also be used as strain-indicators in glaciers. We develop a multi-scale homogenization model for the constitutive response of bubbly-ice by treating it as a three-phase polycrystalline composite, where pressurized bubbles are embedded inside the polycrystalline matrix. The model predicts that microstructural textures developed in response to different loading conditions significantly influence the macroscopic response.

CBE Doctoral Defense: "Alternating Multi-block Polyethylenes with Associating Groups: Self-Assembled Nanoscale Morphologies and Ion Transport"
2019-07-15 10:00 - 12:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Committee: Karen Winey, Advisor; Daeyeon Lee, Robert Riggleman and Chinedum Osuji

CBE Doctoral Dissertation Defense: "Alternating Multiblock Polyethylenes with Associating Groups: Self-Assembled Nanoscale Morphologies and Ion Transport"
2019-07-15 10:00 - 12:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Thesis Committee: Karen Winey, Advisor; Daeyeon Lee, Robert Riggleman and Chinedum Osuji

BE Seminar: Next Generation Orthobiologics: Advanced Growth Factor and Biomaterials Engineering
2019-07-09 10:30 - 11:30 | Class of 62 Auditorium, John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA, 19104
The standard of care for augmenting surgical bone repair or regeneration remains bone graft harvested from the patient despite a lack of sufficient quantity or quality of graft in many clinical cases. Bone morphogenetic protein (BMP) therapeutics have been successfully developed and commercially marketed as substitutes for bone graft. Although the clinical success of BMP, especially in spinal fusion, is well-documented, safety issues related to the required therapeutic dose, sub-optimal delivery and off-label use have generated substantial controversy. To address these issues and develop a next generation BMP product with improved efficacy and safety, we designed a series of novel recombinant human chimeric proteins with enhanced binding affinities to key cellular receptors involved in bone formation. In parallel, a novel biomaterial scaffold was developed to improve the local retention time of these “designer” BMPs and reduce the risk of adverse events. Through this combination of protein engineering and specialized biomaterial development, large animal studies have demonstrated efficacy at substantially lower doses than those required with existing BMP products and the potential to provide a safer and more effective option for surgeons and patients.

MEAM Seminar: "Effect of Nanoparticle Size on the Mechanical Properties of Nanoparticle (NP) Assemblies"
2019-06-26 15:30 - 17:00 | Moore 212
Nanoparticle assemblies (NPAs) have attracted tremendous interests of various research communities. The particle-size-effect on mechanical properties of NPAs is systematically studied. With decreasing the particle size d from 300 nm to 10 nm, the SiO2 NPAs become drastically harder (∼39×), stiffer (∼15×), and tougher (>3.5×). The results are consistent with the data scattered in the literature for various nanoparticle (NP) systems, indicating a fundamentally universal d-effect for all NPAs. A model is developed to correlate the hardness and the NP junction (NPJ) strength f. Here, f is mainly due to van der Waals and capillary interactions, roughly a constant (140 nN) for d = 100–300 nm, and then f decreases with decreasing d from ∼100 nm. The deformation mechanism of NPAs (for indentation depth ≫d) is shear plasticity involving shear breaking of NPJs. The fundamental mechanism for the d-effect is that, with decreasing d, the NPJ’s planar density increases much faster than the decrease of f. Moreover, three deformation mechanisms of NPAs, (1) nanoparticle dislodging, (2) shear-band formation, and (3) cracking are naturally d-dependent. These new findings can provide important insights into the fundamental understanding of the inter-NP interaction, the mechanical behavior of the NPAs, and the design of robust NP-based devices. If time allows, as an independent topic, the experimental characterization of freestanding membrane will also be briefly discussed.

MEAM Seminar: “Thermalization of Bulk Magnetic Materials in Spin-Lattice Dynamics Simulations”
2019-06-25 10:30 - 12:00 | Moore 216, 200 S. 33rd Street, Philadelphia, PA, 19104, United States
Spin-lattice dynamics (SLD), an increasingly popular simulation method which simultaneously computes both atomic displacements and spins, offer new possibilities for modeling the temporal evolution of systems where the coupling between these atomic features are relevant such as spin caloritronics, heat assisted magnetic recording, magnetocaloric responses and magnetic nanoparticle hyperthermia. To accurately model and understand these magnetic materials, SLD must capture spin-spin and spin-lattice interactions in a physically meaningful way. Recent work indicates that including a local magnetic anisotropy term in SLD simulations may be necessary to appropriately couple the magnetic spins to the atomic system to allow for thermal transport between the systems. A key obstacle to the adoption of this term is the lack of knowledge of its parameters for a broad range of materials. Ab initio calculations can obtain these parameters, but these calculations are limited by energy scales, system size and computational cost. A new framework using bulk experimental properties is introduced to obtain these parameters which avoids some or all of these challenges of the ab initio method. Results from this framework are discussed for iron along with the validation procedure for the found parameters.

MEAM Seminar: "Machine Learning for Robotics: Achieving Safety, Performance and Reliability by Combining Models and Data in a Closed-Loop System Architecture"
2019-06-18 10:30 - 12:00 | Moore 216, 200 S. 33rd Street, Philadelphia, PA, 19104, United States
The ultimate promise of robotics is to design devices that can physically interact with the world. To date, robots have been primarily deployed in highly structured and predictable environments. However, we envision the next generation of robots (ranging from self-driving and -flying vehicles to robot assistants) to operate in unpredictable and generally unknown environments alongside humans. This challenges current robot algorithms, which have been largely based on a-priori knowledge about the system and its environment. While research has shown that robots are able to learn new skills from experience and adapt to unknown situations, these results have been limited to learning single tasks, and demonstrated in simulation or lab settings. The next challenge is to enable robot learning in real-world application scenarios. This will require versatile, data-efficient and online learning algorithms that guarantee safety when placed in a closed-loop system architecture. It will also require to answer the fundamental question of how to design learning architectures for dynamic and interactive agents. This talk will highlight our recent progress in combining learning methods with formal results from control theory. By combining models with data, our algorithms achieve adaptation to changing conditions during long-term operation, data-efficient multi-robot, multi-task transfer learning, and safe reinforcement learning. We demonstrate our algorithms in vision-based off-road driving and drone flight experiments, as well as on mobile manipulators.

MEAM Seminar: "Hierarchical Task-Parameterized Learning from Demonstration "
2019-06-11 10:30 - 12:00 | Moore 216, 200 S. 33rd Street, Philadelphia, PA, 19104, United States
Many modern humanoid robots are designed to operate in human environments, like homes and hospitals. Such robots could help humans accomplish tasks and lower their physical and/or mental workload. However, robot users in homes and hospitals typically are not familiar with robotics or programming, therefore it is difficult for them to adapt robots to their specific needs and environments. To remedy this situation, many researchers turn to learning from demonstration (LfD), which enables a robot to emulate natural human movement as opposed to having an operator devise control policies and reprogram the robot for every new situation it encounters.
We suggest a hierarchical LfD structure of task-parameterized models, particularly for object movement tasks that are ubiquitous in everyday life and could benefit from robotic support. Inspired by the task-parameterized Gaussian mixture model (TP-GMM) algorithm, we develop the hierarchical structure and explicitly utilize task parameters to maximize the expected performance in a new situation from a few demonstrated situations. The robot can thus determine when it should request new demonstrations when the expected performance is too low. Other advantages of our approach include that a wider range of task situations can be modeled in the same framework without deteriorating performance and that adding or removing demonstrations incurs low computational load, and thus the robot’s skill library can be built incrementally. We show these advantages in a simulated task and in the real world where naïve participants collaborated with a Willow Garage PR2 robot to move a handheld object. For most tested scenarios our hierarchical method achieved significantly better task performance and subjective ratings than both a passive model with only gravity compensation and a single TP-GMM encoding all demonstrations.

NSF CAREER Awards Workshop
2019-06-10 11:00 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
