Curvature-dependent tension and tangential flows at the interface of motility-induced phases

Adam Patch, Daniel M. Sussman, David Yllanes, M Cristina Marchetti

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Purely repulsive active particles spontaneously undergo motility-induced phase separation (MIPS) into condensed and dilute phases. Remarkably, the mechanical tension measured along the interface between these phases is negative. In equilibrium this would imply an unstable interface that wants to expand, but these out-of-equilibrium systems display long-time stability and have intrinsically stiff boundaries. Here, we study this phenomenon in detail using active Brownian particle simulations and a novel frame of reference. By shifting from the global (or laboratory) frame to a local frame that follows the dynamics of the phase boundary, we observe correlations between the local curvature of the interface and the measured value of the tension. Importantly, our analysis reveals that curvature drives sustained local tangential motion of particles within a surface layer in both the gas and the dense regions. The combined tangential current in the gas and local "self-shearing" of the surface of the dense phase suggest a stiffening interface that redirects particles along itself to heal local fluctuations. These currents restore the otherwise wildly fluctuating interface through an out-of-equilibrium Marangoni effect. We discuss the implications of our observations on phenomenological models of interfacial dynamics.

Original languageEnglish (US)
Pages (from-to)7435-7445
Number of pages11
JournalSoft Matter
Volume14
Issue number36
DOIs
StatePublished - Jan 1 2018

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locomotion
Gases
curvature
Phase boundaries
Shearing
Phase separation
stiffening
display devices
shearing
gases
surface layers
simulation

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

Cite this

Curvature-dependent tension and tangential flows at the interface of motility-induced phases. / Patch, Adam; Sussman, Daniel M.; Yllanes, David; Marchetti, M Cristina.

In: Soft Matter, Vol. 14, No. 36, 01.01.2018, p. 7435-7445.

Research output: Contribution to journalArticle

Patch, A, Sussman, DM, Yllanes, D & Marchetti, MC 2018, 'Curvature-dependent tension and tangential flows at the interface of motility-induced phases', Soft Matter, vol. 14, no. 36, pp. 7435-7445. https://doi.org/10.1039/c8sm00899j
Patch, Adam ; Sussman, Daniel M. ; Yllanes, David ; Marchetti, M Cristina. / Curvature-dependent tension and tangential flows at the interface of motility-induced phases. In: Soft Matter. 2018 ; Vol. 14, No. 36. pp. 7435-7445.
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