Dynamics-dependent density distribution in active suspensions

Abstract

Self-propelled colloids constitute an important class of intrinsically non-equilibrium matter. Typically, such a particle moves ballistically at short times, but eventually changes its orientation, and displays random-walk behavior in the long-time limit. Theory predicts that if the velocity of non-interacting swimmers varies spatially in 1D, $v(x)$, then their density $\rho (x)$ satisfies $\rho (x)=\rho (0)v(0)/v(x)$, where $x=0$ is an arbitrary reference point. Such a dependence of steady-state $\rho (x)$ on the particle dynamics, which was the qualitative basis of recent work demonstrating how to `paint' with bacteria, is forbidden in thermal equilibrium. We verify this prediction quantitatively by constructing bacteria that swim with an intensity-dependent speed when illuminated. A spatial light pattern therefore creates a speed profile, along which we find that, indeed, $\rho (x)v(x)=\mathrm{constant}$, provided that steady state is reached.

References in corpus (16)

• The Mechanics and Statistics of Active Matter
• Swimming in circles: Motion of bacteria near solid boundaries
• Statistical Mechanics of Interacting Run-and-Tumble Bacteria
• Active Brownian Motion Tunable by Light
• Differential Dynamic Microscopy: Probing wave vector dependent dynamics with a microscope
• Sedimentation, trapping, and rectification of dilute bacteria
• Towards a 'Thermodynamics' of Active Matter
• Differential Dynamic Microscopy of Bacterial Motility
• Dynamic density shaping of light driven bacteria
• Painting with bacteria: Smart templated self assembly using motile bacteria
• Differential Dynamic Microscopy: a High-Throughput Method for Characterizing the Motility of Microorganism
• Light-induced self-assembly of active rectification devices
• The role of correlations in the collective behaviour of microswimmer suspensions
• Dynamics-dependent density distribution in active suspensions
• Osmotaxis in Escherichia coli through changes in motor speed
• Correcting artifacts from finite image size in Differential Dynamic Microscopy

Cited by in corpus (17)

• Statistical Mechanics of Active Ornstein Uhlenbeck Particles
• Time-(ir)reversibility in active matter: from micro to macro
• Feedback-Controlled Active Brownian Colloids with Space-Dependent Rotational Dynamics
• Dynamics-dependent density distribution in active suspensions
• Characterization and Control of the Run-and-Tumble Dynamics of {\it Escherichia Coli}
• Lamellar to micellar phases and beyond: when tactic active systems admit free-energy functionals
• Dynamics of active particles with space-dependent swim velocity
• Photo-bioconvection: towards light-control of flows in active suspensions
• Ramifications of disorder on active particles in one dimension
• Optimisation of an active heat engine
• Sizing multimodal suspensions with differential dynamic microscopy
• Swimming suppresses correlations in dilute suspensions of pusher microorganisms
• Activity-induced propulsion of a vesicle
• Influence of density-dependent diffusion on pattern formation in a refuge
• Phase separation of chemokinetic active particles
• Run-and-tumble particle with saturating rates
• Propagating Density Spikes in Light-Powered Motility-Ratchets