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  • Open Access

Excitability and Oscillations of Active Droplets

Ivar S. Haugerud1, Hidde D. Vuijk1, Job Boekhoven2, and Christoph A. Weber1,*

  • 1Faculty of Mathematics, Natural Sciences, and Materials Engineering: Institute of Physics, University of Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany
  • 2School of Natural Sciences, Department of Bioscience, Technical University of Munich, Lichtenbergstraße 4, 85748 Garching, Germany

  • *Contact author: christoph.weber@uni-a.de
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Phys. Rev. Lett. 136, 218401 – Published 27 May, 2026

DOI: https://doi.org/10.1103/g9dh-ymx9

Abstract

In the field of biomolecular condensates and synthetic systems, it is an open question whether liquid droplets can undergo self-sustained oscillations of formation and dissolution. To unravel the minimal physicochemical prerequisite for such droplet oscillations, we present a simple model composed of only two independent chemical components with their diffusive and chemical fluxes governed by nonequilibrium thermodynamics. There is turnover of fuel that maintains a chemical reaction away from equilibrium, leading to active droplets. We find that a single active droplet undergoes a saddle-node bifurcation in the droplet volume upon increasing the fueling strength. Strikingly, the active droplet becomes excitable upon adding a further chemical reaction. For sufficient fueling, the system undergoes self-sustained oscillations.

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Phys. Rev. Lett. 136, 218401– Published 27 May, 2026
  • Received 28 April 2025
  • Revised 4 November 2025
  • Accepted 31 March 2026
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