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.

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.

Activity waves and freestanding vortices in populations of subcritical Quincke rollers

2021 ◽  
Vol 118 (40) ◽  
pp. e2104724118
Author(s):  
Zeng Tao Liu ◽  
Yan Shi ◽  
Yongfeng Zhao ◽  
Hugues Chaté ◽  
Xia-qing Shi ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Electric Field ◽  
Colloidal Particles ◽  
Threshold Field ◽  
Active Matter ◽  
Active Particles ◽  
Fast Activity ◽  
Excitable Systems ◽  
Dc Electric Field ◽  
The Many

Virtually all of the many active matter systems studied so far are made of units (biofilaments, cells, colloidal particles, robots, animals, etc.) that move even when they are alone or isolated. Their collective properties continue to fascinate, and we now understand better how they are unique to the bulk transduction of energy into work. Here we demonstrate that systems in which isolated but potentially active particles do not move can exhibit specific and remarkable collective properties. Combining experiments, theory, and numerical simulations, we show that such subcritical active matter can be realized with Quincke rollers, that is, dielectric colloidal particles immersed in a conducting fluid subjected to a vertical DC electric field. Working below the threshold field value marking the onset of motion for a single colloid, we find fast activity waves, reminiscent of excitable systems, and stable, arbitrarily large self-standing vortices made of thousands of particles moving at the same speed. Our theoretical model accounts for these phenomena and shows how they can arise in the absence of confining boundaries and individual chirality. We argue that our findings imply that a faithful description of the collective properties of Quincke rollers need to consider the fluid surrounding particles.

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 Shape-programmed 3D printed swimming microtori for the transport of passive and active agents

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Remmi Danae Baker ◽  
Thomas Montenegro-Johnson ◽  
Anton D. Sediako ◽  
Murray J. Thomson ◽  
Ayusman Sen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
3D Printing ◽  
Colloidal Particles ◽  
Behavioral Responses ◽  
Active Matter ◽  
Second Mode ◽  
3D Printed ◽  
Complex Fluid ◽  
Bimetallic Nanorods ◽  
Behavioral Mode

Abstract Through billions of years of evolution, microorganisms mastered unique swimming behaviors to thrive in complex fluid environments. Limitations in nanofabrication have thus far hindered the ability to design and program synthetic swimmers with the same abilities. Here we encode multi-behavioral responses in microscopic self-propelled tori using nanoscale 3D printing. We show experimentally and theoretically that the tori continuously transition between two primary swimming modes in response to a magnetic field. The tori also manipulated and transported other artificial swimmers, bimetallic nanorods, as well as passive colloidal particles. In the first behavioral mode, the tori accumulated and transported nanorods; in the second mode, nanorods aligned along the toriʼs self-generated streamlines. Our results indicate that such shape-programmed microswimmers have a potential to manipulate biological active matter, e.g. bacteria or cells.

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.

Experimental Investigation on the Electrokinetic Motions of Colloidal Particles at an Interfacial Boundary Between Solid and Liquid

2019 ◽  
Author(s):  
Katsuaki Shirai ◽  
Shoichiro Kaji ◽  
Shigeo Hosokawa ◽  
Tsuyoshi Kawanami ◽  
Shigeki Hirasawa
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Electric Fields ◽  
Spatial Resolution ◽  
Measurement System ◽  
Colloidal Particles ◽  
Solid Wall ◽  
Wall Region ◽  
And Performance ◽  
Solid Liquid

Abstract We investigate electrokinetic behavior of colloidal particles in the vicinity of a solid-liquid interface. Colloidal liquids are expected to be used as thermal transport media for heat transfer applications such as nanofluids and phase change emulsions. They contain submicrometer-sized particles in liquid, and electrokinetic behavior of the solute particles should play an important role in the heat transfer between solid-liquid interfacing boundaries. However, experimental investigation of the behavior remains difficult due to the required spatial resolution beyond diffraction limit. We developed a measurement system based on laser Doppler principle using an interference of evanescent waves generated at total internal reflections of incident lasers at a solid wall. The system was developed for the measurement of velocities of colloidal particles at an interfacing boundary of colloidal liquid and a solid wall. The system has a unique advantage of a high spatial resolution in the direction perpendicular to the boundary due to the short penetration depth of an evanescent wave in the range of a few hundred nanometers. The principle and performance of the measurement system were investigated using a scanning probe in the measurement volume. We experimentally confirmed the validity of the measurement and characterized the uncertainty of velocity measurement. The system was further applied in a series of measurements of alumina particles dispersed in water in a square-shaped cell under induced electric fields. The measured velocities are proportional to the field strengths at different particle concentrations. The linear relationship is consistent with theoretical predictions, which demonstrates the feasibility of the system for the measurement of velocities of colloidal particles in the near wall region.

Clustering and phase separation in mixtures of dipolar and active particles

Soft Matter ◽  
2020 ◽  
Vol 16 (15) ◽  
pp. 3779-3791 ◽  
Author(s):  
Ryan C. Maloney ◽  
Guo-Jun Liao ◽  
Sabine H. L. Klapp ◽  
Carol K. Hall
Keyword(s):  
Phase Separation ◽  
Colloidal Particles ◽  
Active Particles

Mixtures of dipolar and active colloidal particles display a variety of states including chains, string-fluids, and motility induced phase separation.

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.

scholarly journals Pattern-induced local symmetry breaking in active-matter systems

2020 ◽  
Vol 117 (50) ◽  
pp. 31623-31630
Author(s):  
Jonas Denk ◽  
Erwin Frey
Keyword(s):  
Symmetry Breaking ◽  
Biological Systems ◽  
Local Symmetry ◽  
Theoretical Explanation ◽  
Feedback Mechanism ◽  
Hydrodynamic Theory ◽  
Active Matter ◽  
Theoretical Understanding ◽  
Self Organized ◽  
Microscopic Interactions

The emergence of macroscopic order and patterns is a central paradigm in systems of (self-)propelled agents and a key component in the structuring of many biological systems. The relationships between the ordering process and the underlying microscopic interactions have been extensively explored both experimentally and theoretically. While emerging patterns often show one specific symmetry (e.g., nematic lane patterns or polarized traveling flocks), depending on the symmetry of the alignment interactions patterns with different symmetries can apparently coexist. Indeed, recent experiments with an actomysin motility assay suggest that polar and nematic patterns of actin filaments can interact and dynamically transform into each other. However, theoretical understanding of the mechanism responsible remains elusive. Here, we present a kinetic approach complemented by a hydrodynamic theory for agents with mixed alignment symmetries, which captures the experimentally observed phenomenology and provides a theoretical explanation for the coexistence and interaction of patterns with different symmetries. We show that local, pattern-induced symmetry breaking can account for dynamically coexisting patterns with different symmetries. Specifically, in a regime with moderate densities and a weak polar bias in the alignment interaction, nematic bands show a local symmetry-breaking instability within their high-density core region, which induces the formation of polar waves along the bands. These instabilities eventually result in a self-organized system of nematic bands and polar waves that dynamically transform into each other. Our study reveals a mutual feedback mechanism between pattern formation and local symmetry breaking in active matter that has interesting consequences for structure formation in biological systems.

A Dripping Faucet as a Nonextensive System

2004 ◽  
Author(s):  
T. J. P. Penna ◽  
J. C. Sartorelli
Keyword(s):  
Long Range ◽  
Statistical Physics ◽  
Chaotic Behavior ◽  
Initial Conditions ◽  
Power Laws ◽  
Main Task ◽  
Nonextensive Statistical Mechanics ◽  
System A ◽  
Microscopic Interactions ◽  
Probability Densities

Here we present our attempt to characterize a time series of drop-to-drop intervals from a dripping faucet as a nonextensive system. We found a long-range anticorrelated behavior as evidence of memory in the dynamics of our system. The hypothesis of faucets dripping at the edge of chaos is reinforced by results of the linear rate of the increase of the nonextensive Tsallis statistics. We also present some similarities between dripping faucets and healthy hearts…. Many systems in Nature exhibit complex or chaotic behaviors. Chaotic behavior is characterized by short-range correlations and strong sensitivity to small changes of the initial conditions. Complex behavior is characterized by the presence of long-range power-law correlations in its dynamics. In the latter, the sensitivity to a perturbation of the initial condition is weaker than in the former. Because the probability densities are frequently described as inverse power laws, the variance and the mean often diverge. Although it is hard to predict the long-term behavior of such systems, it is still possible to get some information from them and even to find similarities between two apparently very distinct systems. Tools from statistical physics are frequently used because the main task here is to deal with diverse macroscopic phenomena and to try to explain them, starting with the microscopic interactions among many individual components. The microscopic interactions are not necessarily complicated, but the collective behavior can determine a rather intricate macroscopic description. Nonextensive statistical mechanics, since its proposal in 1988 [27], has been applied to an impressive collection of systems in which spatial or temporal longrange correlations appear. Hence, it can also become a useful tool to characterize such systems. Here, we present an attempt of using such formalism to try to understand the intriguing behavior of an apparently simple system: a dripping faucet.

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