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  • Letter
  • Open Access

Phase separation in a mixture of proliferating and motile active matter

Lukas Hupe1, Joanna M. Materska2, David Zwicker1, Ramin Golestanian1,3,*, Bartlomiej Waclaw2,4,†, and Philip Bittihn1,‡

  • *Contact author: ramin.golestanian@ds.mpg.de
  • †Contact author: bwaclaw@ed.ac.uk
  • ‡Contact author: philip.bittihn@ds.mpg.de
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Phys. Rev. Research 8, L022012 – Published 13 April, 2026

DOI: https://doi.org/10.1103/9pns-h5ll

Abstract

Proliferation and motility are ubiquitous drivers of activity in biological systems. Here, we study a dense binary mixture of motile and proliferating particles with exclusively repulsive interactions, where homeostasis in the proliferating subpopulation is maintained by pressure-induced removal. Using numerical simulations, we show that phase separation emerges naturally in this system at high density and weak enough self-propulsion. We map the full two-component system to an effective single-component active Brownian particle model that recapitulates this behavior. This allows us to identify the emergent effects of the proliferating matrix on motile particles that interact to produce phase separation: enhanced diffusion, renormalized self-propulsion, reduced persistence, and an effective attraction between motile particles. Our results establish a specific type of phase transition based on these emergent effects and pave a way to reinterpret the physics of dense cellular populations, such as bacterial colonies or tumors, as systems of mixed active matter.

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Phys. Rev. Research 8, L022012– Published 13 April, 2026
  • Received 11 June 2025
  • Accepted 9 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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