Non-Gaussian Displacements in Active Transport on a Carpet of Motile Cells

We study the dynamics of micron-sized particles on a layer of motile cells. This cell carpet acts as an active bath that propels passive tracer particles via direct mechanical contact. The resulting nonequilibrium transport shows a crossover from superdiffusive to normal-diffusive dynamics. The particle displacement distribution is distinctly non-Gaussian even at macroscopic timescales exceeding the measurement time. We obtain the distribution of diffusion coefficients from the experimental data and introduce a model for the displacement distribution that matches the experimentally observed non-Gaussian statistics. We argue why similar transport properties are expected for many composite active matter systems.Received 25 October 2023Revised 10 January 2024Accepted 24 January 2024DOI:https://doi.org/10.1103/PhysRevLett.132.088301© 2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAnomalous diffusionBiological fluid dynamicsTransport phenomenaPhysical SystemsCellsLiving matter & active matterMicroswimmersInterdisciplinary PhysicsStatistical Physics & ThermodynamicsPhysics of Living Systems