Publications
27 results found
Bertrand T, d'Alessandro J, Maitra A, et al., 2024, Clustering and ordering in cell assemblies with generic asymmetric aligning interactions, Physical Review Research, Vol: 6, ISSN: 2643-1564
Collective cell migration plays an essential role in various biological processes, such as development or cancer proliferation. While cell-cell interactions are clearly key determinants of collective cell migration, the physical mechanisms that control the emergence of cell clustering and collective cell migration are still poorly understood. In particular, observations have shown that binary cell-cell collisions generally lead to antialignment of cell polarities and separation of pairs—a process called contact inhibition of locomotion (CIL), which is expected to disfavor the formation of large-scale cell clusters with coherent motion even though the latter is often observed in tissues. To solve this puzzle, we adopt a joint experimental and theoretical approach to determine the large-scale dynamics of cell assemblies from elementary pairwise cell-cell interaction rules. We quantify experimentally binary cell-cell interactions and show that they can be captured by a minimal equilibriumlike pairwise asymmetric aligning interaction potential that reproduces the CIL phenomenology. We identify its symmetry class, build the corresponding active hydrodynamic theory, and show on general grounds that such asymmetric aligning interaction destroys large-scale clustering and ordering, leading instead to a liquidlike microphase of cell clusters of finite size and short lived polarity or to a fully dispersed isotropic phase. Finally, this shows that CIL-like asymmetric interactions in cellular systems—or general active systems—control cluster sizes and polarity, and can prevent large-scale coarsening and long-range polarity, except in the singular regime of dense confluent systems.
Anand S, Lee CF, Bertrand T, 2024, Active Jamming at Criticality, Physical Review Research, ISSN: 2643-1564
Alston H, Cocconi L, Bertrand T, 2023, Irreversibility across a Nonreciprocal PT-Symmetry-Breaking Phase Transition., Phys Rev Lett, Vol: 131
Nonreciprocal interactions are commonplace in continuum-level descriptions of both biological and synthetic active matter, yet studies addressing their implications for time reversibility have so far been limited to microscopic models. Here, we derive a general expression for the average rate of informational entropy production in the most generic mixture of conserved phase fields with nonreciprocal couplings and additive conservative noise. For the particular case of a binary system with Cahn-Hilliard dynamics augmented by nonreciprocal cross-diffusion terms, we observe a nontrivial scaling of the entropy production rate across a parity-time symmetry breaking phase transition. We derive a closed-form analytic expression in the weak-noise regime for the entropy production rate due to the emergence of a macroscopic dynamic phase, showing it can be written in terms of the global polar order parameter, a measure of parity-time symmetry breaking.
Killeen A, Bertrand T, Lee CF, 2023, Modeling growing confluent tissues using a lattice Boltzmann method: interface stability and fluctuations, Physical Review Research, Vol: 5, ISSN: 2643-1564
Tissue growth underpins a wide array of biological and developmental processes, and numerical modeling of growing systems has been shown to be a useful tool for understanding these processes. However, the phenomena that can be captured are often limited by the size of systems that can be modeled. Here, we address this limitation by introducing a lattice Boltzmann method (LBM) for a growing system that is able to efficiently model hydrodynamic length scales. The model incorporates a bounce-back approach to describing the growing front of a tissue, which we use to investigate the dynamics of the interface of growing model tissues. We find that the interface grows with scaling in agreement with the Kardar-Parisi-Zhang (KPZ) universality class when growth in the system is bulk driven. Interestingly, we also find the emergence of a previously unreported hydrodynamic instability when proliferation is restricted to the tissue edge. We then develop an analytical theory to show that the instability arises due to a coupling between the number of cells actively proliferating and the position of the interface.
Cocconi L, Alston H, Bertrand T, 2023, Active bound states arise from transiently nonreciprocal pair interactions, Physical Review Research, Vol: 5, ISSN: 2643-1564
Static nonreciprocal forces between particles generically drive persistent motion reminiscent of self-propulsion. Here, we demonstrate that reciprocity-breaking fluctuations about a reciprocal mean coupling strength are sufficient to generate this behavior in a minimal two-particle model, with the velocity of the ensuing active bound state being modulated in time according to the nature of these fluctuations. To characterize the ensuing nonequilibrium dynamics, we derive exact results for the time-dependent center of mass mean-square displacement and average rate of entropy production for two simple examples of discrete- and continuous-state fluctuations in one dimension. We find that the resulting dimer can exhibit unbiased persistent motion akin to that of an active particle, leading to a significantly enhanced effective diffusivity.
Marrec L, Bank C, Bertrand T, 2023, Solving the stochastic dynamics of population growth, ECOLOGY AND EVOLUTION, Vol: 13, ISSN: 2045-7758
Alston H, Parry AO, Voituriez R, et al., 2022, Intermittent attractive interactions lead to microphase separation in nonmotile active matter, Physical Review E: Statistical, Nonlinear, and Soft Matter Physics, Vol: 106, ISSN: 1539-3755
Nonmotile active matter exhibits a wide range of nonequilibrium collective phenomena yet examples are crucially lacking in the literature. We present a microscopic model inspired by the bacteria Neisseria meningitidis in which diffusive agents feel intermittent attractive forces. Through a formal coarse-graining procedure, we show that this truly scalar model of active matter exhibits the time-reversal-symmetry breaking terms defining the Active Model B+ class. In particular, we confirm the presence of microphase separation by solving the kinetic equations numerically. We show that the switching rate controlling the interactions provides a regulation mechanism tuning the typical cluster size, e.g., in populations of bacteria interacting via type IV pili.
Alston H, Cocconi L, Bertrand T, 2022, Non-equilibrium thermodynamics of diffusion in fluctuating potentials, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 55, ISSN: 1751-8113
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- Citations: 3
Bertrand T, Lee CF, 2022, Diversity of phase transitions and phase separations in active fluids, Physical Review Research, Vol: 4, ISSN: 2643-1564
Active matter is not only indispensable to our understanding of diverse biological processes, but also provides a fertile ground for discovering novel physics. Many emergent properties impossible for equilibrium systems have been demonstrated in active systems. These emergent features include motility-induced phase separation, a long-ranged ordered (collective motion) phase in two dimensions, and order-disorder phase coexistences (banding and reverse-banding regimes). Here, we unify these diverse phase transitions and phase coexistences into a single formulation based on generic hydrodynamic equations for active fluids. We also reveal a novel comoving coexistence phase and a multicritical point.
Killeen A, Bertrand T, Lee CF, 2022, Polar fluctuations lead to extensile nematic behavior in confluent tissues, Physical Review Letters, Vol: 128, Pages: 1-6, ISSN: 0031-9007
How can a collection of motile cells, each generating contractile nematic stresses in isolation, become an extensile nematic at the tissue-level? Understanding this seemingly contradictory experimental observation, which occurs irrespective of whether the tissue is in the liquid or solid states, is not only crucial to our understanding of diverse biological processes, but is also of fundamental interest to soft matter and many-body physics. Here, we resolve this cellular to tissue level disconnect in the small fluctuation regime by using analytical theories based on hydrodynamic descriptions of confluent tissues, in both liquid and solid states. Specifically, we show that a collection of microscopic constituents with no inherently nematic extensile forces can exhibit active extensile nematic behavior when subject to polar fluctuating forces. We further support our findings byperforming cell level simulations of minimal models of confluent tissues.
Golovkova I, Montel L, Pan F, et al., 2021, Adhesion as a trigger of droplet polarization in flowing emulsions, SOFT MATTER, Vol: 17, Pages: 3820-3828, ISSN: 1744-683X
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- Citations: 5
Golovkova I, Montel L, Wandersman E, et al., 2020, Depletion attraction impairs the plasticity of emulsions flowing in a constriction, SOFT MATTER, Vol: 16, Pages: 3294-3302, ISSN: 1744-683X
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- Citations: 9
Bertrand T, Chatenay D, voituriez R, 2019, Nonlinear diffusion and hyperuniformity from Poisson representation in systems with interaction mediated dynamics, New Journal of Physics, Vol: 21, ISSN: 1367-2630
We introduce a minimal model of interacting particles relying on conservation of the number of particles and interactions respecting conservation of the center of mass. The dynamics in our model is directly amenable to simple pairwise interactions between particles leading to particle displacements, ensues from this what we call interaction mediated dynamics. Inspired by binary reaction kinetics-like rules, we model systems of interacting agents activated upon pairwise contact. Using Poisson representations, our model is amenable to an exact nonlinear stochastic differential equation. We derive analytically its hydrodynamic limit, which turns out to be a nonlinear diffusion equation of porous medium type valid even far from steady state. We obtain exact self-similar solutions with subdiffusive scaling and compact support. The nonequilibrium steady state of our model in the dense phase displays hyperuniformity which we are able to predict from our analytical approach. We reinterpret hyperuniformity as stemming from correlations in particles displacements induced by the conservation of center of mass. Although quite simplistic, this model could in principle be realized experimentally at different scales by active particles systems.
Xiong F, Wang P, Clark AH, et al., 2019, Comparison of shear and compression jammed packings of frictional disks, GRANULAR MATTER, Vol: 21, ISSN: 1434-5021
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- Citations: 8
Wu Q, Cui C, Bertrand T, et al., 2019, Active acoustic switches using two-dimensional granular crystals, Physical Review E, Vol: 99, ISSN: 2470-0045
Bertrand T, Ilien P, Benichou O, et al., 2018, Dynamics of run-and-tumble particles in dense single-file systems, NEW JOURNAL OF PHYSICS, Vol: 20, ISSN: 1367-2630
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- Citations: 11
Chen S, Bertrand T, Jin W, et al., 2018, Stress anisotropy in shear-jammed packings of frictionless disks, Physical Review E, Vol: 98, ISSN: 2470-0045
Bertrand T, Zhao Y, Benichou O, et al., 2018, Optimized Diffusion of Run-and-Tumble Particles in Crowded Environments, PHYSICAL REVIEW LETTERS, Vol: 120, ISSN: 0031-9007
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- Citations: 40
Wu Q, Bertrand T, Shattuck MD, et al., 2017, Response of jammed packings to thermal fluctuations, PHYSICAL REVIEW E, Vol: 96, ISSN: 2470-0045
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- Citations: 6
Bares J, Wang D, Wang D, et al., 2017, Local and global avalanches in a two-dimensional sheared granular medium, PHYSICAL REVIEW E, Vol: 96, ISSN: 2470-0045
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- Citations: 56
Bertrand T, Peixinho J, Mukhopadhyay S, et al., 2016, Dynamics of Swelling and Drying in a Spherical Gel, PHYSICAL REVIEW APPLIED, Vol: 6, ISSN: 2331-7019
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- Citations: 93
Bertrand T, Behringer RP, Chakraborty B, et al., 2016, Protocol dependence of the jamming transition, PHYSICAL REVIEW E, Vol: 93, ISSN: 1539-3755
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- Citations: 39
Bertrand T, Schreck CF, O'Hern CS, et al., 2014, Hypocoordinated solids in particulate media, PHYSICAL REVIEW E, Vol: 89, ISSN: 1539-3755
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- Citations: 14
van Deen MS, Bertrand T, Nhung V, et al., 2013, Particles accelerate the detachment of viscous liquids, RHEOLOGICA ACTA, Vol: 52, Pages: 403-412, ISSN: 0035-4511
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- Citations: 32
Bertrand T, Bonnoit C, Clement E, et al., 2012, Dynamics of drop formation in granular suspensions: the role of volume fraction, GRANULAR MATTER, Vol: 14, Pages: 169-174, ISSN: 1434-5021
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- Citations: 33
Bonnoit C, Bertrand T, Clement E, et al., 2012, Accelerated drop detachment in granular suspensions, PHYSICS OF FLUIDS, Vol: 24, ISSN: 1070-6631
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- Citations: 59
Schreck CF, Bertrand T, O'Hern CS, et al., 2011, Repulsive Contact Interactions Make Jammed Particulate Systems Inherently Nonharmonic, PHYSICAL REVIEW LETTERS, Vol: 107, ISSN: 0031-9007
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- Citations: 68
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