Article
Polymer Science
Shensheng Chen, Pengfei Zhang, Zhen-Gang Wang
Summary: In this study, dissipative particle dynamics was used to investigate the behavior of polyelectrolyte complexes in dilute solutions. The results show that net-charged macromolecular clusters are formed in the systems, which depends on the overall charge asymmetry. When the charge ratio reaches a threshold value, the polyions condense into a single large coacervate cluster. The addition of salt leads to salting-out and salting-in phenomena, and the length and concentration asymmetry play significant roles in polyelectrolyte complex coacervation.
Article
Chemistry, Physical
Roni Kroll, Yoav Tsori
Summary: We propose a model that describes ion-induced nucleation in fluids, which can be induced by various charged particles such as molecular aggregates, large ions, colloids, or aerosol particles. This model extends the Thomson model to polar environments and solves the Poisson-Boltzmann equation to determine the potential profiles and energy around the charged core. Our results are analytical under the Debye-Huckel limit and numerical otherwise. By analyzing the Gibbs free energy curve, we identify the metastable and stable states, as well as the energy barrier between them, under different saturation values, core charges, and salt concentrations. Additionally, we calculate the phase lines in the phase diagram of supersaturation and core charge, revealing different regions of electro-prewetting, spontaneous nucleation, ion-induced nucleation, and classical-like nucleation.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2023)
Article
Polymer Science
Robert J. S. Ivancic, Sara Orski, Debra J. Audus
Summary: The experimental challenges in characterizing the structure of branched polymers can be overcome by using molecular dynamics models to simulate their properties. This study focuses on linear low-density polyethylene (LLDPE) and develops a model that replicates all-atom simulations and experiments. The relationship between branched and linear dilute solution properties is tested using this model, and a general theory for the dilute solution properties of linear polymers with linear side-chain branches is proposed.
Article
Physics, Fluids & Plasmas
Arjun Sharma, Donald L. Koch
Summary: We studied the steady-state extensional rheology of a suspension of spherical particles in a dilute polymer solution using the FENE-P constitutive relation. Our results showed that the stress of the system is influenced by the Einstein viscosity, the polymer influence on the stresslet, and the particle-induced polymer stress. The presence of the particles created regions of both larger and smaller local stretching compared to undisturbed flow, and the extensional viscosity of the suspension decreased with the addition of particles.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Thermodynamics
Saeed Parvar, Carlos B. da Silva, Fernando Pinho
Summary: This paper proposes an approximate self-similar solution for the thermal boundary layer flow, and investigates the effects of viscoelasticity and viscous dissipation on the boundary layer characteristics. At low elasticity levels, the solution exhibits global self-similar behavior, but as the flow elasticity increases, the self-similarity is lost and elasticity-dependent results show local variations.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Biochemical Research Methods
Meng-Yu Tsai, Leia Fan, Jessica Tseng, Jason Lin, Andy Tseng, Eric Lee
Summary: This study presents an analytical formula to calculate the motion of droplets with arbitrary surface potentials in a dilute electrolyte solution. Viscosity affects the speed of movement for dielectric droplets, while it has the opposite effect for conducting droplets. The presence of a spinning electric driving force on the droplet surface is responsible for this difference.
Article
Chemistry, Physical
Yoshiharu Suzuki, Satoshi Takeya
Summary: Metastable forms of ice and their crystal growth are crucial in various areas. This study investigates the effects of solute on the crystal growth of ice in dilute solution and reveals the inhibitory effect of trehalose on ice crystal growth, which results in easier sublimation of ice.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
A. Scotti, M. Pelaez-Fernandez, U. Gasser, A. Fernandez-Nieves
Summary: The osmotic pressure of both ionic and neutral microgel solutions is primarily determined by the behavior of free ions leaving the microgel periphery to maximize entropy, rather than the translational degrees of freedom of the microgels themselves. Microgels are energetically favorable to maintain a constant volume without significant deswelling up to a certain concentration. The concentration at which deswelling begins weakly depends on the crosslinker concentration, which impacts microgel size; this can be explained by examining the relationship between osmotic pressure, microgel bulk modulus, and particle size.
Article
Chemistry, Physical
Mohit Singh, Yoav Tsori
Summary: In this study, the orientation transitions of uncharged peanut-shaped polystyrene colloids under different electric field conditions were investigated experimentally and theoretically. The results show that the colloids exhibit different orientation states depending on the applied potential and electric field frequency.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2022)
Article
Mechanics
Raul Fernandez-Mateo, Pablo Garcia-Sanchez, Victor Calero, Hywel Morgan, Antonio Ramos
Summary: Quadrupolar electro-osmotic flows are experimentally demonstrated around charged dielectric microspheres in an electrolyte under an alternating current electric field. An electrokinetic model is presented to predict flow characteristics based on surface conductance and polarization of electrolyte concentration. These flows, known as concentration polarization electro-osmosis, are anticipated to play a major role in the assembly of colloids and manipulation of dielectric micro- and nanoparticles through electric fields.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Multidisciplinary
Praneetha Pulyala, Meng Jing, Wei Gao, Xuanhong Cheng
Summary: This study develops a method to quantify the migration of colloids in a temperature gradient and investigates its variation with the composition and pH of the dispersing medium and the presence of an anionic surfactant at different salt concentrations. The results indicate that the migration behavior is controlled by the solute composition, and the obtained migration coefficient is in agreement with previous theories and findings. Additionally, the thermophobic/thermophilic behavior of particles is strongly influenced by the thermoelectric effect of the buffer ions.
Article
Physics, Multidisciplinary
Ioulia Chikina, Sawako Nakamae, Valeriy Shikin, Andrey Varlamov
Summary: The Seebeck effect in stabilized electrolytes containing colloidal particles exhibits a unique two-stage character, with a linear increase followed by a dramatic drop in differential thermopower. This behavior is attributed to the thermo-diffusion flows of mobile ions and the involvement of colloidal particles in forming the electric field. The steady state thermoelectric effect is characterized by slow thermal diffusion of colloidal particles and loss of their electro-neutrality near electrodes.
Article
Chemistry, Multidisciplinary
Yifei Wang, Sheereen Majd
Summary: Phase separation in lipid membranes is controlled by the presence and amount of charged lipids. This study shows that the inclusion of charged lipids with saturated tails can suppress phase separation in multicomponent membranes. The effect is dependent on the membrane surface charge density and can be neutralized by the inclusion of oppositely charged lipids or divalent cations.
Article
Multidisciplinary Sciences
Scott M. Fenton, Poornima Padmanabhan, Brian K. Ryu, Tuan T. D. Nguyen, Roseanna N. Zia, Matthew E. Helgeson
Summary: Colloidal gelation is a method to form processable soft solids using various functional materials. The microscopic processes during gelation that differentiate different types of gels are not well understood. This study presents a method that predicts the minimal conditions for gel solidification and connects the quench path to the emergence of gelled states. The results show that all gels incorporate elements of percolation, phase separation, and glassy arrest, and the slope of the gelation boundary corresponds to the dominant gelation mechanism.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Multidisciplinary Sciences
Marjolein N. van der Linden, Jeffrey C. Everts, Rene van Roij, Alfons van Blaaderen
Summary: This study demonstrates experimentally that the Brazil-nut effect can be achieved in a system of charged colloids driven by Brownian motion and electrostatics without external forces. Theoretical analysis shows that the mass-per-charge ratio of the heavier particles must be smaller than that of the lighter particles, and at high overall density, the system can be trapped in a long-lived metastable state, preventing the occurrence of the equilibrium Brazil-nut effect. This work provides valuable insights into the physics of strongly interacting systems and has implications for understanding sedimentation experiments with charged colloids.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Chemistry, Physical
Niklas O. Junker, Farzaneh Vaghefikia, Alyazan Albarghash, Henning Hoefig, Daryan Kempe, Julia Walter, Julia Otten, Martina Pohl, Alexandros Katranidis, Simone Wiegand, Joerg Fitter
JOURNAL OF PHYSICAL CHEMISTRY B
(2019)
Article
Chemistry, Physical
Doreen Niether, Simone Wiegand
EUROPEAN PHYSICAL JOURNAL E
(2019)
Article
Chemistry, Physical
Mona Sarter, Doreen Niether, Bernd W. Koenig, Wiebke Lohstroh, Michaela Zamponi, Niina H. Jalarvo, Simone Wiegand, Joerg Fitter, Andreas M. Stadler
JOURNAL OF PHYSICAL CHEMISTRY B
(2020)
Article
Polymer Science
Doreen Niether, Mona Sarter, Bernd W. Koenig, Joerg Fitter, Andreas M. Stadler, Simone Wiegand
Review
Physics, Multidisciplinary
Namkyu Lee, Simone Wiegand
Article
Chemistry, Physical
Shilpa Mohanakumar, Jutta Luettmer-Strathmann, Simone Wiegand
Summary: Thermophoresis is a sensitive tool for monitoring protein-ligand binding, but the microscopic mechanisms in protein systems are still poorly understood due to the challenges of separating the effects of the protein system from added buffers. This study systematically investigates the thermodiffusion of aqueous potassium salt solutions, aiming to achieve a more fundamental understanding of the thermodiffusion of proteins. Comparisons with non-ionic solutes and discussions on ion-specific solvation provide insights into the thermophoresis of salts in protein systems.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Antara Pal, Md Arif Kamal, Thomas Zinn, Jan K. G. Dhont, Peter Schurtenberger
Summary: The study investigates the influence of external magnetic fields on the anisotropic collective dynamics of core/shell colloidal cubes with hematite cores and silica shells. Results show that these micrometer-sized particles self-assemble into chains and sediment to form higher-order structures, with dynamics following compressed exponential behavior in different directions with respect to the external field, indicating hyperdiffusive behavior. The anomalous dynamics are believed to be caused by the inhomogeneous distribution of stress points resulting from external field-induced alignment of chains.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Chemistry, Physical
Shilpa Mohanakumar, Simone Wiegand
Summary: Specific ion effects are important in scientific and technological processes, influencing the hydrogen bond network and leading to a specific order of ions. Thermal diffusion mass transport is sensitive to changes in the hydrogen bond network and can be ranked based on the hydrophilicity of the salt. The study investigates the thermal diffusion of various sodium salts in water, comparing the results with corresponding potassium salts.
EUROPEAN PHYSICAL JOURNAL E
(2022)
Article
Chemistry, Physical
Namkyu Lee, Dzmitry Afanasenkau, Philipp Rinklin, Bernhard Wolfrum, Simone Wiegand
Summary: This study introduces a thermophoretic lab-on-a-chip device for measuring the Soret coefficient using resistive heating of a microwire and FLIM. Through monitoring concentration profile of colloidal particles in a temperature field, the functionality of the device is verified. The results demonstrate that this chip offers a simple way to study thermophoretic behavior of biological systems in multicomponent buffer solutions.
EUROPEAN PHYSICAL JOURNAL E
(2021)
Article
Thermodynamics
Namkyu Lee, Shilpa Mohanakumar, Simone Wiegand
Summary: Thermodiffusion or thermophoresis has gained significant interest in various engineering fields. This study proposes a thermophoretic microfluidic cell that enables quantitative measurements of the Soret coefficient of colloids. The cell utilizes fluorescence lifetime imaging microscopy to measure the spatial temperature profile and fluorescence intensity to monitor the concentration profile. The measured Soret coefficients with the cell show good agreement with those determined using a Thermal Diffusion Forced Rayleigh Scattering setup, with an average difference of less than 8%.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Biochemistry & Molecular Biology
Shilpa Mohanakumar, Namkyu Lee, Simone Wiegand
Summary: In this study, we compared data obtained from the non-equilibrium process of thermal diffusion forced Rayleigh scattering (TDFRS) with data obtained from the equilibrium process of isothermal titration calorimetry (ITC). The results showed that the thermophoretic behavior quantified by the Soret coefficient S_T agreed with the Gibb's free energy Delta G determined in the ITC experiment. We also investigated the influence of fluorescent labeling on the binding behavior and found that the dye had a significant impact.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Chemistry, Physical
Shilpa Mohanakumar, Hartmut Kriegs, W. J. Briels, Simone Wiegand
Summary: This study investigates the thermodiffusive properties of aqueous solutions of sodium iodide, potassium iodide, and lithium iodide. The Soret coefficient of all systems exhibits a non-monotonic variation with concentration, with a minimum value observed at a concentration of 1 mol kg(-1) of solvent in all three cases, indicating the similarity of relevant length and energy scales. The study proposes an intuitive model based on the behavior of fully hydrated salt molecules, including water molecules that behave differently from bulk water. Preliminary calculations suggest that the Soret coefficients begin to increase beyond concentrations where fully hydrated particles are randomly close packed, indicating potential limitations of the model at high concentrations.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Zihan Tan, Vania Calandrini, Jan K. G. Dhont, Gerhard Naegele, Roland G. Winkler
Summary: This study introduces a MPC implementation for layered immiscible fluids, exhibiting accurate flow profile simulations and shear stress functions. Additionally, the model is capable of determining the hydrodynamic mobilities of colloidal spheres near fluid-fluid interfaces. While computationally efficient, the model may not reproduce all hydrodynamic features of an ideally flat interface between immiscible fluids.
Article
Chemistry, Physical
Chunli Wang, Zhihao Zhang, Xiaoheng Fu, Jing Zhang, Jan K. G. Dhont
Summary: The study quantitatively determined the content of interfacial and bulk water in the parental microemulsions using FTIR spectroscopy, and investigated the nucleation and growth of PbCrO4 nanoparticles in the microemulsions. By controlling the water ratio in micellar droplets, the researchers were able to obtain amorphous nanoparticles in the interfacial water and nanocrystals in the bulk water. The amorphous nanoparticles with defined shapes were found to be stable in the microemulsion solution and did not transform into crystallites for several days, offering a method to control the metastable amorphous precursor for follow-up crystallization.
MOLECULAR SYSTEMS DESIGN & ENGINEERING
(2021)
Article
Chemistry, Physical
J. K. G. Dhont, G. W. Park, W. J. Briels
Summary: The study derives expressions for the pair-correlation function for active Brownian particles (ABPs) with short-ranged direct interactions under different swimming velocities and concentrations, providing insights into the interactions between ABPs.
