Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStructural correlations in diffusiophoretic colloidal mixtures with nonreciprocal interactions
100
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Nonreciprocal effective interaction forces can occur between mesoscopic particles in colloidal suspensions that are driven out of equilibrium. These forces violate Newtons third law actio=reactio on coarse-grained length and time scales. Here we explore the statistical mechanics of Brownian particles with nonreciprocal effective interactions. Our model system is a binary fluid mixture of spherically symmetric, diffusiophoretic mesoscopic particles, and we focus on the time-averaged particle pair- and triplet-correlation functions. Based on the many-body Smoluchowski equation we develop a microscopic statistical theory for the particle correlations and test it by computer simulations. For model systems in two and three spatial dimensions, we show that nonreciprocity induces distinct nonequilibrium pair correlations. Our predictions can be tested in experiments with chemotactic colloidal suspensions.
rate research
Read More
The dynamics of a spherical chemically-powered synthetic colloidal motor that operates by a self-diffusiophoretic mechanism and has a catalytic domain of arbitrary shape is studied using both continuum theory and particle-based simulations. The motor executes active rotational motion when self-generated concentration gradients and interactions between the chemical species and colloidal motor surface break spherical symmetry. Local variations of chemical reaction rates on the motor catalytic surface with catalytic domain sizes and shapes provide such broken symmetry conditions. A continuum theoretical description of the active rotational motion is given, along with the results of particle-based simulations of the active dynamics. From these results a detailed description of the factors responsible for the active rotational dynamics can be given. Since active rotational motion often plays a significant part in the nature of the collective dynamics of many-motor systems and can be used to control motor motion in targeted cargo transport, our results should find applications beyond those considered here.
We analyze the phonon spectra of periodic structures formed by two-dimensional mixtures of dipolar colloidal particles. These mixtures display an enormous variety of complex ordered configurations [J. Fornleitner {it et al.}, Soft Matter {bf 4}, 480 (2008)], allowing for the systematic investigation of the ensuing phonon spectra and the control of phononic gaps. We show how the shape of the phonon bands and the number and width of the phonon gaps can be controlled by changing the susceptibility ratio, the concentration and the mass ratio between the two components.
Gravity can affect colloidal suspensions since for micrometer-sized particles gravitational and thermal energies can be comparable over vertical length scales of a few millimeters. In mixtures, each species possesses a different buoyant mass, which can make experimental results counter-intuitive and difficult to interpret. Here, we revisit from a theoretical perspective iconic sedimentation-diffusion-equilibrium experiments on colloidal plate-rod mixtures by van der Kooij and Lekkerkerker. We reproduce their findings, including the observation of five different mesophases in a single cuvette. Using sedimentation path theory, we incorporate gravity into a microscopic theory for the bulk of a plate-rod mixture. We also show how to disentangle the effects of gravity from sedimentation experiments to obtain the bulk behavior and make predictions that can be experimentally tested. These include changes in the sequence by altering the sample height. We demonstrate that both buoyant mass ratio and sample height form control parameters to study bulk phase behavior.
The influence of an external field acting differently on the two constituents of a binary colloidal mixture performing Brownian dynamics is investigated by computer simulations and a simple theory. In our model, one half of the particles ($A$-particles) are pulled by an external force ${vec F}^{(A)}$ while the other half of them ($B$-particles) are pulled by an external force ${vec F}^{(B)}$. If ${vec F}^{(A)}$ and ${vec F}^{(B)}$ are parallel and the field-free state is a mixed fluid, previous simulations (J. Dzubiella et al, Phys. Rev. E {bf 65} 021402 (2002)) have shown a nonequilibrium pattern formation involving lanes of $A$ or $B$ particles only which are sliding against each other in the direction of the external forces. In this paper, we generalize the situation both to non-parallel external forces and to field-free crystalline states. For non-parallel forces, lane formation is also observed but with an orientation {it tilted} with respect to the external forces. If the field-free state is crystalline, a continuous increase of the parallel external forces yields a novel {it reentrant freezing} behavior: the crystal first melts mechanically via the external force and then recrystallizes into demixed crystalline lanes sliding against each other.
We identify a structural one-body force field that sustains spatial inhomogeneities in nonequilibrium overdamped Brownian many-body systems. The structural force is perpendicular to the local flow direction, it is free of viscous dissipation, it is microscopically resolved in both space and and time, and it can stabilize density gradients. From the time evolution in the exact (Smoluchowski) low-density limit, Brownian dynamics simulations and a novel power functional approximation, we obtain a quantitative understanding of viscous and structural forces, including memory and shear migration.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
