Active Particle Diffusion in Convection Roll Arrays

2021 ◽  
Author(s):  
Pulak Kumar Ghosh ◽  
Fabio Marchesoni ◽  
Yunyun Li ◽  
Franco Nori
Keyword(s):  
Active Particle ◽  
Particle Diffusion ◽  
Active Matter ◽  
Active Particles ◽  
Convection Roll ◽  
Small Scales

Undesired advection effects are unavoidable in most nano-technological applications involving active matter. However, it is conceivable to govern the transport of active particles at the small scales by suitably tuning...

scholarly journals Oscillating collective motion of active rotors in confinement

2020 ◽  
Vol 117 (22) ◽  
pp. 11901-11907 ◽  
Author(s):  
Peng Liu ◽  
Hongwei Zhu ◽  
Ying Zeng ◽  
Guangle Du ◽  
Luhui Ning ◽  
...  
Keyword(s):  
Collective Behavior ◽  
Collective Motion ◽  
Dynamic Structure ◽  
Packing Fraction ◽  
Frictional Stress ◽  
Active Matter ◽  
Active Particles ◽  
Particle Level ◽  
Inhomogeneous Density ◽  
Oscillation Properties

Due to its inherent out-of-equilibrium nature, active matter in confinement may exhibit collective behavior absent in unconfined systems. Extensive studies have indicated that hydrodynamic or steric interactions between active particles and boundary play an important role in the emergence of collective behavior. However, besides introducing external couplings at the single-particle level, the confinement also induces an inhomogeneous density distribution due to particle-position correlations, whose effect on collective behavior remains unclear. Here, we investigate this effect in a minimal chiral active matter composed of self-spinning rotors through simulation, experiment, and theory. We find that the density inhomogeneity leads to a position-dependent frictional stress that results from interrotor friction and couples the spin to the translation of the particles, which can then drive a striking spatially oscillating collective motion of the chiral active matter along the confinement boundary. Moreover, depending on the oscillation properties, the collective behavior has three different modes as the packing fraction varies. The structural origins of the transitions between the different modes are well identified by the percolation of solid-like regions or the occurrence of defect-induced particle rearrangement. Our results thus show that the confinement-induced inhomogeneity, dynamic structure, and compressibility have significant influences on collective behavior of active matter and should be properly taken into account.

Dry Aligning Dilute Active Matter

2020 ◽  
Vol 11 (1) ◽  
pp. 189-212 ◽  
Author(s):  
Hugues Chaté
Keyword(s):  
Long Range ◽  
Collective Motion ◽  
Local Level ◽  
Orientational Order ◽  
Two Dimensions ◽  
Active Matter ◽  
Long Range Correlations ◽  
Active Particles ◽  
Growing Domain

Active matter physics is about systems in which energy is dissipated at some local level to produce work. This is a generic situation, particularly in the living world but not only. What is at stake is the understanding of the fascinating, sometimes counterintuitive, emerging phenomena observed, from collective motion in animal groups to in vitro dynamical self-organization of motor proteins and biofilaments. Dry aligning dilute active matter (DADAM) is a corner of the multidimensional, fast-growing domain of active matter that has both historical and theoretical importance for the entire field. This restrictive setting only involves self-propulsion/activity, alignment, and noise, yet unexpected collective properties can emerge from it. This review provides a personal but synthetic and coherent overview of DADAM, focusing on the collective-level phenomenology of simple active particle models representing basic classes of systems and on the solutions of the continuous hydrodynamic theories that can be derived from them. The obvious fact that orientational order is advected by the aligning active particles at play is shown to be at the root of the most striking properties of DADAM systems: ( a) direct transitions to orientational order are not observed; ( b) instead generic phase separation occurs with a coexistence phase involving inhomogeneous nonlinear structures; ( c) orientational order, which can be long range even in two dimensions, is accompanied by long-range correlations and anomalous fluctuations; ( d) defects are not point-like, topologically bound objects.

Inelastic cross sections of nucleons and π mesons in carbon and lead near 100 GeV

1968 ◽  
Vol 46 (10) ◽  
pp. S694-S696 ◽  
Author(s):  
A. V. Alakoz ◽  
V. N. Bolotov ◽  
M. I. Devishev ◽  
L. F. Klimanova ◽  
A. P. Shmeleva
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Cosmic Ray ◽  
High Energy ◽  
Active Particle ◽  
Particle Interactions ◽  
Active Particles ◽  
The Cross

An experiment to measure the cross section for high-energy cosmic-ray neutrons and charged nuclear-active particle interactions with Pb and C nuclei has been carried out at an altitude of 2 000 m. Large spark chambers were used in a detector which selected neutrons and charged nuclear-active particles in the region of 100 GeV. The results are σπ(nPb) = (1.65 ± 0.17) barn, σπ(nC) = (0.204 ± 0.02) barn, σπ(πPb) = (1.53 ± 0.17) barn, σπ(πC) = (0.168 ± 0.017) barn.

scholarly journals Active droploids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jens Grauer ◽  
Falko Schmidt ◽  
Jesús Pineda ◽  
Benjamin Midtvedt ◽  
Hartmut Löwen ◽  
...  
Keyword(s):  
Free Energy ◽  
Energy Flow ◽  
Colloidal Particles ◽  
Light Illumination ◽  
Active Matter ◽  
Form Complex ◽  
Droplet Shape ◽  
Active Particles ◽  
Complex Patterns ◽  
Environmental Feedback

AbstractActive matter comprises self-driven units, such as bacteria and synthetic microswimmers, that can spontaneously form complex patterns and assemble into functional microdevices. These processes are possible thanks to the out-of-equilibrium nature of active-matter systems, fueled by a one-way free-energy flow from the environment into the system. Here, we take the next step in the evolution of active matter by realizing a two-way coupling between active particles and their environment, where active particles act back on the environment giving rise to the formation of superstructures. In experiments and simulations we observe that, under light-illumination, colloidal particles and their near-critical environment create mutually-coupled co-evolving structures. These structures unify in the form of active superstructures featuring a droplet shape and a colloidal engine inducing self-propulsion. We call them active droploids—a portmanteau of droplet and colloids. Our results provide a pathway to create active superstructures through environmental feedback.

scholarly journals Pinning dislocations in colloidal crystals with active particles that seek stacking faults

Soft Matter ◽  
2020 ◽  
Vol 16 (17) ◽  
pp. 4182-4191
Author(s):  
Bryan VanSaders ◽  
Sharon C. Glotzer
Keyword(s):  
Stacking Faults ◽  
Colloidal Crystals ◽  
Active Particle ◽  
Host Crystal ◽  
Active Particles ◽  
Dislocation Defects

By designing the shape of an active particle, its transport through a dense crystal can be tailored, as well as its interaction with dislocation defects present in the host crystal.

scholarly journals Force moments of an active particle in a complex fluid

2017 ◽  
Vol 829 ◽  
Author(s):  
Gwynn J. Elfring
Keyword(s):  
Hydrodynamic Force ◽  
Newtonian Fluids ◽  
Active Particle ◽  
Reciprocal Theorem ◽  
Background Flow ◽  
Weakly Nonlinear ◽  
Active Particles ◽  
Special Cases ◽  
Complex Fluid

A generalized reciprocal theorem is formulated for the motion and hydrodynamic force moments of an active particle in an arbitrary background flow of a (weakly nonlinear) complex fluid. This formalism includes as special cases a number of previous calculations of the motion of both passive and active particles in Newtonian and non-Newtonian fluids.

scholarly journals Dependency of active pressure and equation of state on stiffness of wall

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Emad Pirhadi ◽  
Xiang Cheng ◽  
Xin Yong
Keyword(s):  
Colloidal Particles ◽  
Solid Wall ◽  
State Function ◽  
Active Matter ◽  
Mechanical Pressure ◽  
System A ◽  
Active Particles ◽  
Wall Stiffness ◽  
Microscopic Interactions ◽  
Dependent Property

AbstractAutonomous motion and motility are hallmarks of active matter. Active agents, such as biological cells and synthetic colloidal particles, consume internal energy or extract energy from the environment to generate self-propulsion and locomotion. These systems are persistently out of equilibrium due to continuous energy consumption. It is known that pressure is not always a state function for generic active matter. Torque interaction between active constituents and confinement renders the pressure of the system a boundary-dependent property. The mechanical pressure of anisotropic active particles depends on their microscopic interactions with a solid wall. Using self-propelled dumbbells confined by solid walls as a model system, we perform numerical simulations to explore how variations in the wall stiffness influence the mechanical pressure of dry active matter. In contrast to previous findings, we find that mechanical pressure can be independent of the interaction of anisotropic active particles with walls, even in the presence of intrinsic torque interaction. Particularly, the dependency of pressure on the wall stiffness vanishes when the stiffness is above a critical level. In such a limit, the dynamics of dumbbells near the walls are randomized due to the large torque experienced by the dumbbells, leading to the recovery of pressure as a state variable of density.

Collective clog control: Optimizing traffic flow in confined biological and robophysical excavation

Science ◽  
2018 ◽  
Vol 361 (6403) ◽  
pp. 672-677 ◽  
Author(s):  
J. Aguilar ◽  
D. Monaenkova ◽  
V. Linevich ◽  
W. Savoie ◽  
B. Dutta ◽  
...  
Keyword(s):  
Traffic Flow ◽  
Theoretical Models ◽  
Dissolution Time ◽  
Active Matter ◽  
Global Control ◽  
Active Particles ◽  
Robust Strategies

Groups of interacting active particles, insects, or humans can form clusters that hinder the goals of the collective; therefore, development of robust strategies for control of such clogs is essential, particularly in confined environments. Our biological and robophysical excavation experiments, supported by computational and theoretical models, reveal that digging performance can be robustly optimized within the constraints of narrow tunnels by individual idleness and retreating. Tools from the study of dense particulate ensembles elucidate how idleness reduces the frequency of flow-stopping clogs and how selective retreating reduces cluster dissolution time for the rare clusters that still occur. Our results point to strategies by which dense active matter and swarms can become task capable without sophisticated sensing, planning, and global control of the collective.

scholarly journals The force on a boundary in active matter

2015 ◽  
Vol 785 ◽  
Author(s):  
Wen Yan ◽  
John F. Brady
Keyword(s):  
General Theory ◽  
Drag Coefficient ◽  
Time Scales ◽  
Thermal Energy ◽  
Length Scale ◽  
Active Matter ◽  
Run Length ◽  
Active Particles ◽  
Orientation Distributions ◽  
Reorientation Time

We present a general theory for determining the force (and torque) exerted on a boundary (or body) in active matter. The theory extends the description of passive Brownian colloids to self-propelled active particles and applies for all ratios of the thermal energy $k_{B}T$ to the swimmer’s activity $k_{s}T_{s}={\it\zeta}U_{0}^{2}{\it\tau}_{R}/6$, where ${\it\zeta}$ is the Stokes drag coefficient, $U_{0}$ is the swim speed and ${\it\tau}_{R}$ is the reorientation time of the active particles. The theory, which is valid on all length and time scales, has a natural microscopic length scale over which concentration and orientation distributions are confined near boundaries, but the microscopic length does not appear in the force. The swim pressure emerges naturally and dominates the behaviour when the boundary size is large compared to the swimmer’s run length $\ell =U_{0}{\it\tau}_{R}$. The theory is used to predict the motion of bodies of all sizes immersed in active matter.

scholarly journals Delayed feedback control of active particles: a controlled journey towards the destination

2019 ◽  
Vol 21 (25) ◽  
pp. 13776-13787 ◽  
Author(s):  
S. M. J. Khadem ◽  
Sabine H. L. Klapp
Keyword(s):  
Feedback Control ◽  
Real Time ◽  
Delayed Feedback ◽  
Particle Orientation ◽  
Delayed Feedback Control ◽  
Active Particle ◽  
Real Time Monitoring ◽  
Active Particles

Orientation of an active particle could be estimated by comparing its delayed position with the actual one. Therefore, steering process does not require any real-time monitoring of the particle orientation.

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