The Northeast Complex Fluids and Soft Matter Workshop

The 17th Northeast Complex Fluids and Soft Matter Workshop

Nicolas Alvarez

DREXEL UNIVERSITY, CHEMICAL AND BIOLOGICAL ENGINEERING

Abstract
Themoset resins offer significant advantages over thermoplastics, especially in the high performance categories of aerospace and automobile parts. Direct Ink Writing (DIW) and Ambient Reactive Extrusion (ARE) are two scalable additive manufacturing methods used to print/manufacture parts from thermoset resins. Both methods consist of extruding a thermoset resin from a nozzle to deposit filaments (a.k.a. rows) to build up layers, similar to the well-known Fused Deposition Modeling (FDM) process. Unlike FDM, thermosets are relatively low viscosity Newtonian fluids, which makes their deposition challenging. Printability of thermoset resins requires either a rheological modifier, such as colloidal particles, or fast curing reactions during deposition. In the case of fast curing systems, the extruded filament can undergo significant spreading during the curing process. Successful printing requires the anticipation of such shape change to ensure accurate print dimensions and successful cohesion between extruded rows. In the case of rheological modifiers, the thermoset is formulated into a colloidal organogel whose modulus is intended to hold the filament shape during curing. However, the organogels undergo significant shear thinning during the extrusion process, and therefore also experience significant spreading before gelation of the thermoset network. In this work, we develop a numerical simulation model for predicting the shape of filaments during the printing process. Significant emphasis is placed on the dynamic contact angle boundary condition and the rheological properties of the resin formulations. The model is developed and validated with the aid of experimental results on both thermal and photo curing resins. Most importantly, we present a generalized spreading theory using scaling analysis to predict the shape of arbitrary resin systems with a small set of measured parameters. Ultimately, we aim to include these results and predictions in slicing software to predict printing parameters and avoid the Edisonian approach of print optimization.

Biography
Nicolas J. Alvarez earned a BS in Chemical Engineering from the University of Florida in 2006 and a PhD in Chemical Engineering from Carnegie Mellon University in 2011. After three years of postdoctoral work at the Technical University of Denmark in Lyngby, he joined the Department of Chemical and Biological Engineering at Drexel in 2014. Alvarez’s research interests involve development of unique experimental tools to understand and characterize the behavior of polymers and surfactants in nonlinear flows, at interfaces, and in bulk. These tools are used to understand how certain processing windows lead to advantageous material properties. One such tool, used for the characterization of extensional rheology, has been commercialized by Alvarez and colleagues. Alvarez is developing a consortium of companies interested in the development of analytical tools to better understand the relationship between chemical structure, processing, and material performance. Alvarez teaches an elective course on non-Newtonian fluid mechanics that introduces students to real-world materials encountered in modern day chemical plants.

Lina Baroudi

MANHATTAN COLLEGE, MECHANICAL ENGINEERING

• On the Effect of Finite-Size Particles on Flow Instabilities and Transition to Turbulence in Taylor-Couette Flow

Abstract
Inertial flow of particle-laden fluids arises in many natural and industrial settings, e.g., drilling fluids, debris flow, and slurry flow, among others. The fundamental understanding of the influence of fluid inertia on particle-laden flows, connecting to temporal and spatial configurations of particles, is very challenging but has a significant impact on process efficiency and predictability. In this talk, I will present our work on the inertial flow of suspensions of finite-size neutrally buoyant spherical particles in Taylor-Couette geometry. The effect of suspended particles on flow transitions for several particle volume fractions (0≤φ≤0.30) is investigated by means of flow visualization experiments in a flow driven by a rotating inner cylinder for a large range of Reynolds numbers (30≤Re≤4000) covering the laminar and turbulent flow transitions. We show that particles play a fundamental role in the observed instabilities and decrease the threshold at which turbulence can be sustained. We also show that particle concentration distribution in the annular region plays an important role in the stability of the flow structure.

Biography
Dr. Baroudi is an assistant professor in the Department of Mechanical Engineering at Manhattan College, NY. Her research focuses on studying multiphase flows encountered in industrial processes and natural phenomena from a fundamental physical perspective through computational modeling and laboratory experiments. She has investigated different physical problems in surface-tension driven flows. A current focus of her work is on developing a mechanistic understanding and predictive ability of the role of inertia in suspension flows, correlating to dynamics at the particle-level. She received her Ph.D. in Mechanical Engineering from the City College of New York in 2017, after which she joined Manhattan College. In addition, she held a visiting research scientist position in the Department of Mechanical and Aerospace Engineering at NYU and the Department of Chemical and Biomolecular Engineering at the University of Connecticut.

David Grier

NEW YORK UNIVERSITY, PHYSICS

• CATCH: Characterizing and Tracking Colloids Holographically

Abstract
Holograms of colloidal spheres encode a wealth of information on individual particles' position, size and optical properties, all of which can be extracted in real time. Quantitative analysis of colloidal holograms opens doors to new areas of colloid science. Precise three-dimensional tracking of colloidal ensembles, for example, is a boon for microrheology. Part-per-thousand refractive-index measurements enable differentiation of different particle types, with widespread industrial applications. This talk focuses on the nanometer-scale precision that holographic particle characterization can provide for the diameters of individual colloidal spheres. This resolution is good enough to monitor colloidal beads growing in size as molecules bind to their surfaces. Inspired by the COVID-19 pandemic, we used holographic particle characterization to develop a novel platform for label-free bead-based molecular binding assays that we have demonstrated with antibodies to infectious diseases and with viral antigens from SARS-CoV-2 and H1N1 influenza virus. This illustrative example highlights the breadth of fundamental insights and practical applications that can be obtained with this new approach to characterizing and tracking colloids holographically.

Biography
David Grier is a Professor of Physics and Director of the Center for Soft Matter Research at New York University. His research group seeks out nature's fundamental organizing principles through experimental studies on model soft-matter systems, particularly in wave-matter composite systems created with light and sound. Grier received his PhD in Physics from the University of Michigan and was a postdoctoral researcher at AT&T Bell Laboratories before joining the faculty of Physics at the University of Chicago in 1992. He moved to NYU in 2004 as one of the founding members of the CSMR and served two terms as Department Chair. Grier is a Fellow of the National Academy of Inventors, a Fellow of the American Physical Society and Section Secretary for Physics at the AAAS. He was named a Technology Pioneer by the World Economic Forum, and has won three awards for undergraduate teaching at Chicago and NYU.

Alyssa Hensley

STEVENS INSTITUTE OF TECHNOLOGY, CHEMICAL ENGINEERING AND MATERIALS SCIENCE

• Tackling Water Pollution via Sustainable Sorbents: Pb(II) Adsorption by Bio-based Carbons via First Principles Computational Models

Abstract
Accessing clean water―one of the critical components of life and irreplaceable in the agriculture and energy sectors―is currently a global crisis that is growing in severity as the effects of climate change worsen. Bio-based carbons produced from the upgrading of lignocellulosic biomass waste present an opportunity to develop highly efficient and inexpensive sorbents for extraction of heavy metals from watercourses. However, the complex, amorphous nature of bio-based carbons makes it nearly impossible using experiments alone to determine the fundamental, atomic-scale chemical structures, phenomena, and mechanisms that lead to efficient binding of heavy metals. Thus, there is a significant challenge here-in that the design and optimization of highly efficient bio-based carbons is limited by a lack of fundamental chemical insights into the chemical structures present on bio-based carbons and their subsequent ability to interact with and bind heavy metals. We address this challenge here by combining atomic-scale computational models (i.e. density functional theory) with fundamental, statistical mechanics to (1) determine the dominant functionalities present on bio-based carbon sorbents and (2) probe the Pb(II) adsorption mechanism onto these dominant functionalities. Overall, the linkages elucidated here between bio-based carbon sorbent structure and Pb(II) adsorption capacity establish the necessary fundamental chemical design rules to facilitate the rational design of highly efficient bio-based carbon sorbents for water purification.

Biography
Prof. Hensley received her Ph.D. from Washington State University in 2015, during which she won a U.S. Department of Energy Office of Science Graduate Student Research fellowship and worked at the Pacific Northwest National Laboratory. During her time at Washington State University, Prof. Hensley had the opportunity to collaborate closely with researchers at Tufts University on single atom catalysts for low temperature CO oxidation, resulting in publications in high impact journals such as Nature Catalysis, Journal of Catalysis, and The Journal of Physical Chemistry C. Subsequently, Prof. Hensley moved to the University of Toronto as a postdoctoral fellow where she combined kinetic-isotopic experiments with ab initio computational simulations to quantify the atomistic effects of solid-liquid interfaces on the catalytic mechanisms for upgrading biomass-derived phenols to value-added chemicals. Currently, Prof. Hensley is an assistant professor of chemical engineering at Stevens Institute of Technology where research addresses the knowledge-gap in our ability to connect the in situ chemical composition and structure of heterogeneous catalysts to the selective activation of chemical bonds.

Dilhan Kalyon

STEVENS INSTITUTE OF TECHNOLOGY, CHEMICAL ENGINEERING AND MATERIALS SCIENCE

Abstract
The characterization of the shear viscosity material function of viscoplastic fluids is a challenge associated with the binary nature of their deformation behavior in steady simple shear, i.e., solid-like behavior and plug flow at shear stresses that are smaller than the yield stress and fluid-like behavior at shear stresses that are greater than the yield stress, and their ubiquitous slip at the walls of rheometers. Due to these complicating factors most investigators treat the yield stress as a curve fitting parameter obtained upon using rheometer surfaces, intentionally roughened to eliminate wall slip. However, attempts to eliminate wall slip also lead to the fracture of the viscoplastic fluid. We have demonstrated that it is possible to first characterize the wall slip behavior of a viscoplastic fluid followed by the determination of its yield stress and other shear viscosity parameters. Furthermore, recently, we have developed a new and exceptionally simple method for the determination of the yield stress of a viscoplastic fluid, which involves the analysis of the torque versus the apparent shear rate data, collected in steady torsional flow with parallel plates. The new method will enable the facile and accurate determination of the yield stress values of viscoplastic fluids encountered in myriad fields including energetics, ceramics, pharmaceuticals, magnetics, composites, foodstuffs and personal care products.

Biography
Dr. Kalyon has joined Stevens Institute of Technology in 1980, immediately upon completing his PhD in chemical engineering at McGill University. He was appointed as the Founding Director of the Highly Filled Materials Institute in 1989 and Institute Professor in 1999. During the last three years he has served as the Vice Provost of Research and Innovation at Stevens. Prof. Kalyon has received the Thomas Baron award in fluid-particle systems of the American Institute of Chemical Engineers (2008), the International Research award of Society of Plastics Engineers (2008), the Harvey N. Davis Distinguished Teaching Assistant Professor award (1987), Exemplary Research Award (1992), Henry Morton Distinguished Teaching Full Professor award (2000), Honorary M. Eng. degree, honoris causa (1994), the Davis Memorial award for Research Excellence (2009) and the Faculty Appreciation award (2017) from Stevens Institute of Technology, the Founder’s award of JOCG Continuous Extrusion and Mixing Group (2004), and various fellowships including DuPont Central Research and Development Fellowship (1997), Exxon Education Foundation Fellowship (1990) and Unilever Education Fellowship (1991). He was elected Fellow of the Society of Plastics Engineers (2004) and Fellow of American Institute of Chemical Engineering (2006).

Corey O'Hern

YALE UNIVERSITY, MECHANICAL ENGINEERING AND MATERIALS SCIENCE

• Structural, Vibrational, Mechanical Properties of Jammed Packings of Deformable Particles

Abstract
We investigate the structural, vibrational, and mechanical properties of jammed packings of deformable particles with shape degrees of freedom in three dimensions (3D). Each 3D deformable particle is modeled as a surface-triangulated polyhedron, with spherical vertices whose positions are determined by a shape-energy function with terms that constrain the particle surface area, volume, and curvature, and prevent interparticle overlap. We show that jammed packings of deformable particles without bending energy possess low-frequency, quartic vibrational modes, whose number decreases with increasing asphericity and matches the number of missing contacts relative to the isostatic value. In contrast, jammed packings of deformable particles with non-zero bending energy are isostatic in 3D, with no quartic modes. These studies underscore the importance of incorporating particle deformability and shape change when modeling the properties of jammed soft materials.

Biography
Corey O'Hern is a Full Professor in the Department of Mechanical Engineering and Materials Science at Yale University with secondary appointments in Applied Physics, Physics, and the Graduate Program in Computational Biology & Bioinformatics. He also co-founded the Integrated Graduate Program in Physical and Engineering Biology at Yale. He received his Ph.D. in Physics from the University of Pennsylvania in 1999 and then was a postdoctoral fellow at the University of Chicago and UCLA until 2002. In 2017, he was selected as a Fellow of the American Physical Society. Corey is an expert in computational studies of soft matter, which includes granular materials, bubbles and emulsions, as well as biological materials, such as proteins, cells, and tissues. His research group is currently funded by awards from the National Science Foundation, Office of Naval Research, and the National Institutes of Health. He has more than 135 published research articles.

Robert Riggleman

UNIVERSITY OF PENNSYLVANIA, CHEMICAL AND BIOMOLECULAR ENGINEERING

• Failure in Inhomogeneous Polymer Networks

Abstract
Phase separated polymer networks can be synthesized from materials that can provide complimentary properties to the resulting gel, and as a result conetworks formed from glassy and rubbery polymers are emerging as candidates for applications that require both mechanical support and molecular mobility to allow transport. The mechanical and failure properties of these conetworks are only beginning to be studied, and given the nanoscale structure present in conetworks, there are likely to be strong heterogeneities in the properties on the molecular scale. In this talk, I will present our work using coarse-grained molecular dynamics simulations to characterize the dynamic and mechanical properties of polymer networks, including both homogeneous and glassy/rubbery conetworks. By employing a model that allows for bond breaking, we can examine the microscopic mechanism for failure in these networks. In the homogeneous networks, we have extended the classic Lake-Thomas theory that describes failure to account for network defects. For the inhomogeneous networks, we find strong gradients in the mobility near the interface of the microdomains that are homogenized either as the strand length is decreased or the sample is deformed.

Biography
Robert Riggleman is an Associate Professor in the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania in Philadelphia, PA. After obtaining his bachelor's degree in chemical engineering from the University of South Carolina, Columbia, he joined the research groups of Profs. Paul Nealey and Juan de Pablo for his PhD studies, which were completed in 2007. Robert continued to work with Prof. de Pablo briefly as a postdoc before moving on to a second postdoctoral position at the University of California, Santa Barbara, under the advisement of Prof. Glenn Fredrickson. Robert subsequently joined Penn in 2010 as an Assistant Professor and was promoted to Associate Professor with tenure in 2017. Robert’s research interests involve the use of theoretical and computational tools to study the properties of soft matter. A current focus of the group is understanding failure in disordered materials and in the development of novel simulation approaches to study inhomogeneous polymer and composite materials in both equilibrium and non-equilibrium conditions over a range of length scales.