Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Y09: Rheology of Multiphase Systems |
Hide Abstracts |
Sponsoring Units: DSOFT Chair: Reza Foudazi, University of Oklahoma Room: Room 132 |
Friday, March 10, 2023 8:00AM - 8:12AM |
Y09.00001: Analysis of Cerebrospinal Fluid Rheology using Shear and ExtensionalTechniques John Hollister, Won Kim, Anthony Wang, Mayumi L Prins, Christopher C Giza, Pirouz Kavehpour Understanding the rheological behavior of cerebrospinal fluid (CSF)will be critical in the development of head-brain system biomechanicalmodels as well as surgical and medical devices and techniques directedat alleviating intracranial pressure or altering CSF flow. CSF servesmany functions in the head-brain system including cushioning the brainagainst impact, providing nutrient transport, and clearing waste via theglymphatic system. It is derived from blood plasma and is oftenconsidered a protein free Newtonian fluid, since typical CSF proteincontent is found to be between 25-60 mg/100g. However, it has beenshown that the protein content of CSF can be different depending on thelocation (e.g. lumbar vs ventricular shunt) as well as condition of thepatient (e.g. shunt infection, hemorrhage, or obstruction) from whom ithas been extracted. In this study, we have performed a comprehensiverheological analysis of CSF specimens extracted from neurosurgicalpatients at the UCLA hospital. These specimens were tested using aconventional shear rheometer as well as a recently developed micro-extensional technique, which has been shown to be much more sensitiveto protein content of dilute solutions. Preliminary tests show weakextensional behavior consistent with the protein concentration of CSF.The results of this study have shown that CSF exhibits quantifiable non-Newtonian behavior, and that this behavior may be influenced by themedical condition of the patient. Though the non-Newtoniancontribution is relatively small, this characterization of CSF may havesignificant impacts on the development of brain models and medicaltechnologies. |
Friday, March 10, 2023 8:12AM - 8:24AM |
Y09.00002: Rheology of nanoemulsions in glass and compressed-droplet states Reza Foudazi, Zahra Abbasian Chaleshtari The soft matter of interest in this study is concentrated oil-in-water nanoemulsions, in which the content of a polymer depletant is varied. First, dilute nanoemulsions with 25% volume fraction are prepared, containing poly(ethylene glycol)-diacrylate (PEGDA) and sodium dodecyl sulfate (SDS) as depletant and ionic surfactant, respectively. Then, they are concentrated to higher volume fractions through evaporation of continuous phase under controlled conditions. Estimation of the interdroplet interactions and effective volume fractions indicates that nanoemulsions in repulsive glass, attractive glass, and compressed-droplet states can be produced. We evaluate the interfacial tension of water-oil phase and rheological properties of concentrated nanoemulsions. The results show that the equilibrium interfacial tension is independent of PEGDA content. The scaled rheological properties of concentrated nanoemulsions at glass and compressed-droplet states do not superimpose for different contents of PEGDA, which can be attributed to the PEGDA-SDS complexation. |
Friday, March 10, 2023 8:24AM - 8:36AM |
Y09.00003: A Viscoelastic Model with Droplet Breakup Effects for Processing of Dense Emulsions Joseph D Peterson, Vipin Michael, Ioannis Bagkeris In the processing of dense emulsions, complex flows strech and deform droplets to induce breakup, altering the overall distribution of droplet sizes and tuning the mechanical and rheological properties of the final product. For steady homogeneous flows, a droplet's shape and proclivity to breakup can be inferred on the basis of a Capillary number, but more generally a droplet's shape depends its whole history of deformation. This distinction can be particularly important for the complex flow geometries encountered in industrial processing of dense emulsions. To model history-dependence in droplet breakage dynamics, we have developed a new viscoelastic constitutive equation which we call the "shape tensor emulsion population balance" (STEPB) model, built upon an ellipsoidal approximation of droplet shapes. When breakup occurs, complexities of the intermediate breakup process are interpolated via a cascade of binary breakup events, with conservation of capillary stresses at each break. By incorporating population balance terms into the shape evolution equation, our model is the first to present a physical (as opposed to numerical) argument for the log-configuration tensor transform widely used in viscoelastic computational fluid dynamics calculations. In a first application of the STEPB model, we consider non-linear elasticity and droplet breakup in monodisperse dense emulsions under step shear, where we predict non-trivial strain-dependent final daughter droplet distributions. We also compare predictions from STEPB against experimental observations in steady shear flow, illuminating key weaknesses in the model due to neglected terms. |
Friday, March 10, 2023 8:36AM - 8:48AM |
Y09.00004: Dynamics of meniscus-bound particle clusters in extensional flow Sagar Chaudhary, Jovina Vaswani, Sachin S Velankar, Charles M Schroeder Capillary suspensions are three-phase mixtures containing a solid particulate phase, a continuous phase liquid, and a second immiscible liquid. Capillary suspensions have a diverse array of applications in materials science including 3D printing, porous materials, and food formulations. Despite recent progress, the micromechanics of capillary-bound clusters in external flow is not well understood. Here, we study the dynamics of meniscus-bound particle clusters in extensional flow using a Stokes trap, which is an automated flow-based technique that allows for precise control of fluid flow for manipulating and studying freely suspended particle clusters. We observe how clusters rearrange in extensional flow, quantify the capillary number Ca required for rupture, and determine steady-state configurations where particles maintain a finite separation without rupture. Initial experiments focus on the simple case of a two-particle doublet and further extend to multiparticle clusters. Cluster relaxation experiments are performed to observe the time required for clusters to return to their original state starting from a stretched configuration after the flow is stopped. In all cases, experiments are complemented by a mathematical model involving capillary and hydrodynamic drag forces acting on the particles, and good agreement is obtained with experiments. We further aim to determine a critical capillary number Cacr versus relative viscosity phase diagram for particle cluster dynamics, which is analogous to the classic Grace curve for droplet breakup. |
Friday, March 10, 2023 8:48AM - 9:00AM |
Y09.00005: The rheology of colloidal suspensions measured as rod-shaped particles emerge and grow Ryle R Rel, Ryan J McGorty Colloidal rods can significantly alter the rheological properties of suspensions even at low volume fractions due to their anisotropic shape. Understanding the effects of rod volume fraction and anisotropy is necessary for tailoring the rheological properties of suspensions and gels. Many studies have explored the rheology of colloidal rod suspensions, but how the properties of a suspension varies with time as rods form and grow has not been explored. Here, we use bulk rheology to measure the viscoelastic properties of a suspension of polyamide colloidal rods as the rod-shaped particles emerge from a homogeneous surfactant and polyamide solution. By controlling the temperature of the system on our rheometer, we can tune the aspect ratio of the colloidal rods which form. We complement our bulk rheology measurements with microrheology performed using differential dynamic microscopy (DDM). With DDM we find the characteristic timescales of density fluctuations and can determine a confinement length scale for non-ergodic systems. Our work offers new routes for characterizing the rheological properties of colloidal rods and for probing how rods form in a model colloidal system. |
Friday, March 10, 2023 9:00AM - 9:12AM |
Y09.00006: Impact of Structural Heterogeneity and Pre-shearing on the Yielding of "Pristine" Colloidal Gels Christopher W Barney, Megan T Valentine, Matthew E Helgeson Recent studies have introduced a number of kinetic and thermal processing strategies for manipulating the formation of colloidal gels to produce heterogeneous structures. Understanding the impact of controlled structure on gel rheology, including viscoelasticity and yielding, would impact a number of applications in food science, structural materials, and additive manufacturing. However, measuring gel rheology for many systems is made difficult by the necessity for various “pre-shear” and “shear rejuvenation” protocols employed to produce a repeatable initial state of the material for conventional rheometry measurements. This prohibits characterization of gels in their “pristine”, as-formed state, and therefore has been a roadblock in understanding the influence of controlled heterogeneity on gel. To overcome this limitation, we combine a thermoresponsive colloidal system that can be gelled in situ with advanced rheo-microscopy measurements in order to simultaneously measure gel rheology and restructuring in flow, allowing us to assess how large-scale structural heterogeneities, as well as pre-shear, influence the viscoelasticity and yielding of colloidal gels. |
Friday, March 10, 2023 9:12AM - 9:24AM |
Y09.00007: The structure-rheology relationship in three-dimensional sheared lamellar phase : Effect of viscosity contrast Arkaprava Pal, Viswanathan Kumaran
|
Friday, March 10, 2023 9:24AM - 9:36AM |
Y09.00008: Strain-dependent microstructure evolution of ABA triblock gels captured using RheoSAXS Santanu Kundu, Rosa Maria Badani Prado, Satish Mishra, Humayun Ahmad, Wesley R Burghardt ABA triblock copolymer gels dissolved in a B-block selective solvent are being investigated in many applications, from personal products to ballistic applications. Here, we present the transient microstructure of two ABA triblock copolymer gels captured using combined rheology and scattering (RheoSAXS) experiments. These two gels are poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) [PMMA-PnBA-PMMA] dissolved in 2-ethyl-1-hexano1, and poly(styrene)−poly(isoprene)−poly(styrene) [PS−PI−PS] dissolved in mineral oil. The large-amplitude oscillatory strain was applied to these gels, and the microstructural evolution in a given strain cycle was captured. An isotropic scattering profile, typical to gels with A-block aggregates, was observed when no strain was applied. A polydispersed core hard sphere model was used to quantify the microstructural features, such as the size of A-aggregates and the distance between them. In a strain cycle, microstructure oriented in the applied strain direction resulting in an elliptical pattern, and the affine deformation model could capture the data adequately. However, at large strain amplitude, the PS-PI-PS gel displayed both circular and elliptical patterns, indicating some midblocks (B blocks) did not participate in load-bearing, likely caused by strain localization. The polymer concentration, solvent quality, and midblock length play a role in these gels' rheology and microstructure evolution. |
Friday, March 10, 2023 9:36AM - 9:48AM |
Y09.00009: Effects of local incompressibility on the rheology of biocomposite networks Anupama Gannavarapu, Sadjad Arzash, Iain Muntz, Jordan L Shivers, Sihan Chen, Anna-Maria Klianeva, Gijsje H Koenderink, Frederick C MacKintosh Fibrous networks such as collagen are common in biological systems. Recent theoretical and experimental efforts have shed light on the mechanics of single component networks. Most real biopolymer networks, however, are composites made of elements with different rigidity. For instance, extracellular matrix consists of stiff collagen fibers in a soft background matrix. Understanding the interplay between different biopolymer networks remains unclear. In this work, we use 2D coarse-grained models to study the nonlinear strain-stiffening behavior in composites. The local volume constraints due to a soft matrix are implemented by adding an energetic penalty for changes in local density. When subjected to linear shear strain, the composite network was observed to have a substantially stiffer response. As we show, this can be understood in terms of a partial suppression of the non-affine strain due to the local volume constraint. In contrast with the effect of added elastic elements that resist deformation, such as additional springs or fibers, local volume constraints do not lead ultimately to an affine response. We explore the physical compressible and incompressible limits of composite networks by varying material parameters. We further test these predictions in composite collagen-hyaluronan networks that mimic the extracellular matrix of connective tissues. |
Friday, March 10, 2023 9:48AM - 10:00AM |
Y09.00010: BSA Induced Domain Transformations in Polyelectrolyte Complex Hydrogels Holly Senebandith, Samanvaya Srivastava, Advait S Holkar Hydrogels are water-laden three-dimensional (3D) networks which have a myriad of applications. Polyelectrolyte complex (PEC) hydrogels are physically-crosslinked hydrogels that expand the utility of hydrogel materials owing to their electrostatically self-assembled networks formed when two oppositely-charged ABA polyelectrolytes microphase separate (limited by their neutral middle blocks). The resulting polymer dense domains serve as connecting nodes in a 3D polymer network. PEC hydrogels have unique attributes including tunable shear properties, stimuli-responsiveness, and macromolecular entrapment, providing a distinct advantage over covalent hydrogels. The structural evolution of PEC hydrogels when varying polymer concentration, polymer length, and salt has been studied, but their behavior in the presence of proteins has not. In this presentation, we use PEC self-assembly as a tool to guide the model protein, BSA, into PEC hydrogel domains and use small-angle X-ray scattering to elucidate morphological transformations, while unveiling the limits of protein encapsulation. This work demonstrates the ability of PEC hydrogels to act as depots for therapeutics and provides a framework for future development of protein-containing PEC hydrogels for biomedical applications. |
Friday, March 10, 2023 10:00AM - 10:12AM |
Y09.00011: A colloidal model for equilibrium assembly and liquid-liquid phase separation of reflectin protein Tse-Chiang Huang, Robert Levenson, Youli Li, Phillip Kohl, Daniel E Morse, M. Scott Shell, Matthew E Helgeson The reflectin protein is an exceptional example of functional intrinsically disordered protein assembly for its unique ability to modulate the biophotonic camouflage of cephalopods based on its assembly-induced osmotic properties. Although its reversible assembly into discrete, size-controlled clusters and liquid-liquid phase separation droplets is known to depend sensitively on the net protein charge, the detailed molecular mechanisms of reflectin assembly have yet to be identified. Here, we show that reflectin assembly can be explained from a remarkably simple "colloidal atom" model whereby protein molecules interact via a short-range attraction and long-range repulsion (SRA-LRR) pair potential. Through an integrated combination of small angle X-ray scattering and molecular simulations, we demonstrate that coarse grained SRA-LRR interactions, parameterized by experiment, successfully capture a number of quantitative features of reflectin assembly including the pH-dependent formation of discrete-sized nanoclusters as well as liquid-liquid phase separation, resulting in a detailed phase diagram for reflectin assembly. Our results provide predictive capabilities to explain key aspects of native reflectin behavior and to design its assembly in host materials for biophotonic applications. |
Friday, March 10, 2023 10:12AM - 10:24AM |
Y09.00012: Frequentist and Bayesian Approaches to Error Estimation in Particle-Based Simulations of Soft Matter Transport Gerald J Wang Particle-based dynamics (e.g., molecular dynamics, Brownian dynamics, etc.) are used extensively to study transport phenomena in soft matter. In this talk, we describe several recent statistical results governing the quantification of uncertainties associated with the analysis of data from particle-based simulations, both within a frequentist framework and within a Bayesian framework. Using diffusion as measured via the Einstein relation as a case study, we show that commonplace statistical estimators (based upon, e.g., ordinary-least-squares regression) yield substantial and systematic discrepancies for variances of transport quantities, when compared to large-scale/long-time simulations. We present two computationally efficient schemes that can improve error estimates, thereby establishing more credible confidence estimates for particle-based simulations of soft matter transport phenomena. We close by briefly discussing the implications for uncertainty quantification of transport measurements using linear-response-theory-based approaches (e.g., Green-Kubo relations). |
Friday, March 10, 2023 10:24AM - 10:36AM |
Y09.00013: Effects of Electric Charge, Dipole Moment, and Molecular Size on the Viscosity of Ionic Liquids Jester N Itliong, Amalie L Frischknecht, Mark J Stevens, Issei Nakamura The origin of the viscosity of ionic liquids is often unclear and controversial because our understanding of the local dynamics and collective long-range dynamics remains limited. To address this issue, we developed our Stockmayer-fluid molecular dynamics simulation method for ionic liquids that accounts for the electric polarization at the molecular level. Our coarse-grained simulation models consist of minimal sets of model parameters, yet they provide good agreement with the observed viscosity and glass transition temperature of ethylammonium nitrate. We highlight the effects of electric charge, dipole moment, and molecular size on viscosity and glass transition temperature, and discuss the versatility of our simulation method. We show that the rotational dynamics of the ions is critical to account for the experimental observations. In contrast, the effect of the electric charges on the viscosity and glass transition temperature appears relatively weaker. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700