Abstract: In this talk, I will discuss work related to mechanically “programming” soft sensors to respond to a particular mechanical deformation. Advances in 3D-printing, soft polymer fabrication, and other rapid fabrication processes have made the vision of conformal and stretchable mechanical sensors for wearable devices and soft robotics possible. One limitation of these sensors is their low selectivity between different modes of mechanical deformation, such as strain, torsion, and bending.

I will present recent work in enhancing the selectivity of stretchable sensors by using non-planar sensor morphology to bias the sensor towards a particular deformation mode. I will discuss projects including designing a sensor with electrically-tunable sensitivity and the fabrication origami-patterned, deformation-selective flexible sensors.

Biographical Sketch: Kris Dorsey is an assistant professor of engineering in the Picker Engineering Program at Smith College. She was a President’s Postdoctoral Fellow at the University of California, Berkeley and University of California, San Diego. Dr. Dorsey graduated from Carnegie Mellon University with a Ph.D. in Electrical and Computer Engineering and earned her Bachelors of Science in Electrical and Computer Engineering from Olin College.

She founded The MicroSMITHie Lab at Smith College to investigate micro- and miniature-scale sensor design and to prepare undergraduates for graduate study in engineering. Her current research interests include strain-stable, hyperelastic components, novel morphology soft sensors, and sensors for soft robots and wearable devices.

Dr. Dorsey has co-authored several publications on hyperelastic strain sensors, novel soft lithography processes, and the stability of gas chemical sensors. In 2019, she received the NSF CAREER award.

Abstract: Biofilms are surface-attached communities of bacteria that can cause problems including medical infections, fouling, and clogging in industrial applications. By contrast, beneficial biofilms are crucial in applications including waste-water treatment and microbial fuel cells. In this talk, I will discuss about our recent progress in using Vibrio cholerae as a model biofilm former to reveal the mechanical principles underlying biofilm formation, both at the single cell level and at the continuum level. I will first present a new methodology to image living, growing bacterial biofilms at single-cell resolution, and demonstrate how cell-cell adhesion and cell-surface adhesion balance each other to cause V. cholerae to form an ordered, three-dimensional cluster. Next, I will show how extracellular polysaccharides, proteins, and cells function together to define biofilm mechanical and interfacial properties. Finally, I will present various mechanical instabilities that take place when biofilms grow on soft substrates, and how such instabilities, together with interfacial properties, define the morphogenesis process of bacterial biofilms.

Biographical Sketch: Dr. Yan obtained his bachelor’s degree from the College of Chemistry and Molecular Engineering at Peking University in China. As a graduate student, he studied soft matter physics in the Department of Materials Science and Engineering at the University of Illinois, Urbana-Champaign. During his Ph.D., he developed a series of non-equilibrium colloidal materials with dynamic structures controlled by electromagnetic fields. He transitioned to biology for his postdoctoral training, working at Princeton University jointly in the Department of Molecular Biology and the Department of Mechanical and Aerospace Engineering. His current research focus is on bacterial biofilm formation. Dr. Yan received the Career Award at the Scientific Interface from Burroughs Welcome Fund in 2016. He moved to Yale as an Assistant Professor in the Department of Molecular, Cellular and Developmental Biology and Quantitative Biology Institute at Yale University in 2019.

Abstract: Dermal scales appeared early in the evolutionary history of vertebrates, most notably in fishes. Their remarkable multi-functional roles include protection from predatory attacks, enhancement of locomotion, camouflaging and thermal regulation. This has led to a tremendous variation in scale type, material, shape, size and organization among species (e.g. fishes, snakes) as well as within species (different types of fish scales). This has led to a great deal of interest in their material properties. Less investigated is the role of the scales themselves as geometric units of high performance.  Interestingly, many remarkable behaviors lie in the geometrical form and distribution of the scales. Discretely segmented, geometrically pronounced units emanating from softer, slender substrates allows for a rich interplay of deformation, geometry and functions at multiple length scales underscoring structure-property synergy. Therefore, the primitive scale topology (exoskeleton form) appears across a much wider range of critical biological structures such as papillae on feline tongue, where they dramatically enhance gripping capacity and combine it with fluid wicking properties or on the surface of animal furs, where nanoscale scaly features are known to reduce microbial fouling, or aid in aerodynamic functions. Testament to their remarkable structure-properties enhancements, it is difficult to find slender biological structures that do not exploit some type of concerted external surface texture. These features result in a number of unusual mechanical behavior such as small strain reversible nonlinearities and quasi-rigid locking behavior in bending and twisting deformations even when friction is negligible. When friction is significant, unexpected dissipation and damping behaviors arise. Furthermore, stiff plate like scales on a soft substrate can give rise to perceptible change in indentation response, which can quickly transition away from the Hertzian regime. Since the main sources of such nonlinearities are geometry and interface dictated, such extreme mechanical behaviors can be easily programmed and functionally graded using additive manufacturing, which can be exploited for diverse applications such as multifunctional structures, robotic exoskeletons, prosthetics, flexible electronics and protective coatings.

Biographical Sketch: Dr. Ranajay Ghosh is an Assistant Professor in the department of Mechanical and Aerospace Engineering (MAE) and the Center for Advanced Turbine and Energy Research (CATER) at UCF. He directs the Complex Structures and Mechanics of Solids (COSMOS) Laboratory. His research focuses on the behavior of deformable solids and computational mechanics particularly focusing on modeling multiscale and multiphysics phenomena in heterogeneous and topological solids. Prior to his appointment at UCF, Dr. Ghosh earned his PhD from Cornell University, Ithaca, NY where he was awarded the Harriet-Davis doctoral fellowship. During his PhD he also carried out research at the General Electric’s (GE) Global Research Center at Niskayuna, New York where he was the recipient of GE’s global recognition award for outstanding performance. He subsequent carried out postdoctoral research at the Rensselaer Polytechnic Institute and Northeastern University.  Dr. Ghosh’s research work has led to over 45 peer reviewed journal publications including several cover arts and media coverage in Discovery, Newsweek and the New York Times.  Dr. Ghosh’s research is primarily funded by Siemens Energy, the US Department of Energy (DoE) and the National Science Foundation (NSF).

Abstract: Demand of batteries keeps increasing as electronic devices get widespread and fossil-based systems are being replaced by electricity-based systems. Lithium-ion battery has been considered one of the most promising power sources for mobile and transportation systems, but it faces challenging issues of high cost, low capacity (i.e. short operation hours or driving ranges), and safety issues. Therefore, it is necessary to find the break-through technologies to resolve those issues. In this talk, two promising electrochemical systems will be introduced: aluminum-air battery and multi-valent catalytic flow battery. Aluminum is cheap and abundant, benign to the environment, and stable in moisture. But, due to the problems of self-corrosion and formation of inert oxide film on the surface of aluminum during cell operation, the Al-based rechargeable battery could not reach commercialization stage. Ionic liquid which is a molten salt in liquid form at room temperature is getting intense attention recently as a promising electrolyte to resolve those issues. In this talk, discussion will be made about the effect of the oxide film on performance of the ionic-liquid based Al-air battery and how to control the film with results of research conducted in Dr. Cho’s group at Northern Illinois University (NIU) through experiment and physic-based modeling.Redox flow battery (RFB) is enjoying a renaissance with substantial achievement of research, altering it ultra-high performing and high energy dense system. And also, the excellent feature of RFB decoupling energy from power has been applied as a key design factor to overcome the challenging issues of conventional battery systems. In this talk, new promising “redox-mediated bromate based flow battery” which has theoretical energy density greater than lithium ion battery will be introduced, and characteristic “auto-accelerated” catalytic electrochemical reaction coupled with chemical reaction will be discussed in detail.

Biographical Sketch: Dr. Kyu Taek Cho is an assistant professor of mechanical engineering at Northern Illinois University, Dekalb, IL. He has around 20-year experience in the electrochemical system through works in national lab, industry, and academy. He had worked at Lawrence Berkeley National Lab as a postdoc and then a research staff before he joined NIU in 2014. He also has industrial experience as a research engineer at Hyundai Motor Company, S. Korea to develop a fuel stack for the application to vehicle. Dr. Cho has Ph.D. achieved from Pennsylvania State University under guidance of Professor Matthew Mench. Dr. Cho is a director of Electrochemical Energy Lab at NIU to conduct the fundamental research of advanced electrochemical and thermal energy systems.

Abstract: In standard seakeeping simulations of a ship in irregular seas, the rigid body motions of the ship are computed using a set of semi-analytic integro-differential equations, which model the response of the ship including non-linear and history dependent forces.    Using this type of model allows one to model the response of the ship in incident irregular waves, corresponding to a sea state defined by its significant wave height, H_s, peak spectral period, T_p, dominant wave direction, θ₀, and spectrum type, while allowing fairly quick simulation of the response using standard numerical integration methods.  In this work, we develop and apply such a model to compute ship motions for a large number of sea states. Then, we perform the inverse problem of determining the governing sea state parameters by training a Neural Network, based on the time histories of ship response in roll, pitch, and heave computed with the model. The estimator is then validated against physical model test experiments conducted using irregular waves generated in a towing tank to demonstrate that the numerical model is sufficient for training the Neural Network using simulated data.  The main rationale for this work is to develop a low-cost method for small vessels to estimate local sea state conditions in order to avoid operations in dangerous sea states, however the same techniques could be applied in general to transiting vessels to obtain local and continuous sea state measurements for general science purposes or other uses. 

Biographical Sketches: Jason M. Dahl is an Associate Professor in the Department of Ocean Engineering at the University of Rhode Island.  Dr. Dahl (PhD, Ocean Engineering, MIT; B.S., Naval Architecture and Marine Engineering, Webb Institute) is an expert in fluid-structure interactions and floating body dynamics, with particular expertise in the flow-induced vibration of underwater structures. Dr. Dahl has extensive experience as an experimentalist with towing tank operations, dynamic testing, and quantitative flow visualization.

Stephan T. Grilli is a Distinguished Professor and Chair, in the Department of Ocean Engineering at the University of Rhode Island.  Dr. Grilli (PhD, Ocean Engineering, M.S. Physical Oceanography, M.S. Civil Engineering, University of Liège) has a broad background in Computational Fluids Dynamics related to free surface and wave-structure interaction problems in coastal, naval and ocean engineering, and oceanography. Dr. Grilli has over 30 years of experience with developing higher-order boundary element models and viscous simulations for the solution of free surface potential flows for wave propagation and wave-structure interactions including the modeling of tsunami wave propagation, ship seakeeping in waves, wave breaking, and wave energy systems.