Colloidal diffusion in confined geometries

Kim Nygård

doi:10.1039/c7cp02497e

Investigation of Ring and Star Polymers in Confined Geometries: Theory and Simulations

Entropy ◽

10.3390/e23020242 ◽

2021 ◽

Vol 23 (2) ◽

pp. 242

Author(s):

Joanna Halun ◽

Pawel Karbowniczek ◽

Piotr Kuterba ◽

Zoriana Danel

Keyword(s):

Star Polymers ◽

Polymer Chains ◽

The Other ◽

Nano Particles ◽

Dilute Solution ◽

Confined Geometries ◽

Density Profiles ◽

Ideal Ring ◽

Ring Polymer ◽

Monomer Density

The calculations of the dimensionless layer monomer density profiles for a dilute solution of phantom ideal ring polymer chains and star polymers with f=4 arms in a Θ-solvent confined in a slit geometry of two parallel walls with repulsive surfaces and for the mixed case of one repulsive and the other inert surface were performed. Furthermore, taking into account the Derjaguin approximation, the dimensionless layer monomer density profiles for phantom ideal ring polymer chains and star polymers immersed in a solution of big colloidal particles with different adsorbing or repelling properties with respect to polymers were calculated. The density-force relation for the above-mentioned cases was analyzed, and the universal amplitude ratio B was obtained. Taking into account the small sphere expansion allowed obtaining the monomer density profiles for a dilute solution of phantom ideal ring polymers immersed in a solution of small spherical particles, or nano-particles of finite size, which are much smaller than the polymer size and the other characteristic mesoscopic length of the system. We performed molecular dynamics simulations of a dilute solution of linear, ring, and star-shaped polymers with N=300, 300 (360), and 1201 (4 × 300 + 1-star polymer with four arms) beads accordingly. The obtained analytical and numerical results for phantom ring and star polymers are compared with the results for linear polymer chains in confined geometries.

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Impact of confined geometries on hopping and trapping of motile bacteria in porous media

Physical Review E ◽

10.1103/physreve.103.012611 ◽

2021 ◽

Vol 103 (1) ◽

Author(s):

Lazaro J. Perez ◽

Tapomoy Bhattacharjee ◽

Sujit S. Datta ◽

Rishi Parashar ◽

Nicole L. Sund

Keyword(s):

Porous Media ◽

Confined Geometries ◽

Motile Bacteria

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Liquid Crystals in Curved Confined Geometries: Microfluidics Bring New Capabilities for Photonic Applications and Beyond

Langmuir ◽

10.1021/acs.langmuir.1c00256 ◽

2021 ◽

Vol 37 (13) ◽

pp. 3789-3807

Author(s):

Han-Qing Chen ◽

Xi-Yuan Wang ◽

Hari Krishna Bisoyi ◽

Lu-Jian Chen ◽

Quan Li

Keyword(s):

Liquid Crystals ◽

Confined Geometries

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Ferromagnetic 1D oxide nanostructures grown from chemical solutions in confined geometries

Chemical Society Reviews ◽

10.1039/c3cs60288e ◽

2014 ◽

Vol 43 (7) ◽

pp. 2042-2054 ◽

Cited By ~ 17

Author(s):

A. Carretero-Genevrier ◽

T. Puig ◽

X. Obradors ◽

N. Mestres

Keyword(s):

Confined Geometries ◽

Oxide Nanostructures ◽

Chemical Solutions

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The Knudsen Paradox in Micro-Channel Poiseuille Flows with a Symmetric Particle

Applied Sciences ◽

10.3390/app11010351 ◽

2020 ◽

Vol 11 (1) ◽

pp. 351

Author(s):

Ananda Subramani Kannan ◽

Tejas Sharma Bangalore Narahari ◽

Yashas Bharadhwaj ◽

Andreas Mark ◽

Gaetano Sardina ◽

...

Keyword(s):

Flow Behavior ◽

Direct Simulation Monte Carlo ◽

Micro Channel ◽

Confined Geometries ◽

Rarefied Flows ◽

Model Pore ◽

Duct Geometry ◽

Transport Effects ◽

Non Local ◽

Simulation Monte Carlo

The Knudsen paradox—the non-monotonous variation of mass-flow rate with the Knudsen number—is a unique and well-established signature of micro-channel rarefied flows. A particle which is not of insignificant size in relation to the duct geometry can significantly alter the flow behavior when introduced in such a system. In this work, we investigate the effects of a stationary particle on a micro-channel Poiseuille flow, from continuum to free-molecular conditions, using the direct simulation Monte-Carlo (DSMC) method. We establish a hydrodynamic basis for such an investigation by evaluating the flow around the particle and study the blockage effect on the Knudsen paradox. Our results show that with the presence of a particle this paradoxical behavior is altered. The effect is more significant as the particle becomes large and results from a shift towards relatively more ballistic molecular motion at shorter geometrical distances. The need to account for combinations of local and non-local transport effects in modeling reactive gas–solid flows in confined geometries at the nano-scale and in nanofabrication of model pore systems is discussed in relation to these results.

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Magnetic Janssen effect

Nature Communications ◽

10.1038/s41467-021-22722-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

L. Thorens ◽

K. J. Måløy ◽

M. Bourgoin ◽

S. Santucci

Keyword(s):

Magnetic Field ◽

Dynamic Properties ◽

Radial Force ◽

Fine Tuning ◽

Apparent Mass ◽

Confined Geometries ◽

Pairwise Interactions ◽

Janssen Effect ◽

Lateral Walls ◽

Granular Column

AbstractA pile of grains, even when at rest in a silo, can display fascinating properties. One of the most celebrated is the Janssen effect, named after the pioneering engineer who explained the pressure saturation at the bottom of a container filled with corn. This surprising behavior arises because of frictional interactions between the grains through a disordered network of contacts, and the vessel lateral walls, which partially support the weight of the column, decreasing its apparent mass. Here, we demonstrate control over frictional interactions using ferromagnetic grains and an external magnetic field. We show that the anisotropic pairwise interactions between magnetized grains result in a radial force along the walls, whose amplitude and direction is fully determined by the applied magnetic field. Such magnetic Janssen effect allows for the fine tuning of the granular column apparent mass. Our findings pave the way towards the design of functional jammed materials in confined geometries, via a further control of both their static and dynamic properties.

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