# Dynamics-dependent density distribution in active suspensions

Research output: Contribution to journalArticlepeer-review

## 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.
Original language English Nature Communications https://doi.org/10.1038/s41467-019-10283-0 Published - 24 May 2019

## Keywords

• cond-mat.soft

## Fingerprint

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• ### PHYSAPS: The Physics of Active Particle Suspensions

Poon, W.

1/02/1431/01/20

Project: Research

• ### Design Principles for New Soft Materials

EPSRC

7/12/116/06/17

Project: Research

• ### Dynamics-dependent density distribution in active suspensions

Pilizota, T. (Creator), Poon, W. (Creator), Dawson, A. (Creator), Arlt, J. (Creator) & Martinez, V. A. (Creator), Edinburgh DataShare, 24 May 2019

Dataset