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Chen Z, Zheng Y. Persistent and responsive collective motion with adaptive time delay. SCIENCE ADVANCES 2024; 10:eadk3914. [PMID: 38569026 PMCID: PMC10990279 DOI: 10.1126/sciadv.adk3914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 02/29/2024] [Indexed: 04/05/2024]
Abstract
It is beneficial for collective structures to simultaneously have high persistence to environmental noise and high responsivity to nontrivial external stimuli. However, without the ability to differentiate useful information from noise, there is always a tradeoff between persistence and responsivity within the collective structures. To address this, we propose adaptive time delay inspired by the adaptive behavior observed in the school of fish. This strategy is tested using particles powered by optothermal fields coupled with an optical feedback-control system. By applying the adaptive time delay with a proper threshold, we experimentally observe the responsivity of the collective structures enhanced by approximately 1.6 times without sacrificing persistence. Furthermore, we integrate adaptive time delay with long-distance transportation and obstacle-avoidance capabilities to prototype adaptive swarm microrobots. This research demonstrates the potential of adaptive time delay to address the persistence-responsivity tradeoff and lays the foundation for intelligent swarm micro/nanorobots operating in complex environments.
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Affiliation(s)
- Zhihan Chen
- Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA
| | - Yuebing Zheng
- Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
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Chen Z, Ding H, Kollipara PS, Li J, Zheng Y. Synchronous and Fully Steerable Active Particle Systems for Enhanced Mimicking of Collective Motion in Nature. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2304759. [PMID: 37572374 PMCID: PMC10859548 DOI: 10.1002/adma.202304759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/20/2023] [Indexed: 08/14/2023]
Abstract
The collective motion observed in living active matter, such as fish schools and bird flocks, is characterized by its dynamic and complex nature, involving various moving states and transitions. By tailoring physical interactions or incorporating information exchange capabilities, inanimate active particles can exhibit similar behavior. However, the lack of synchronous and arbitrary control over individual particles hinders their use as a test system for the study of more intricate collective motions in living species. Herein, a novel optical feedback control system that enables the mimicry of collective motion observed in living objects using active particles is proposed. This system allows for the experimental investigation of the velocity alignment, a seminal model of collective motion (known as the Vicsek model), in a microscale perturbed environment with controllable and realistic conditions. The spontaneous formation of different moving states and dynamic transitions between these states is observed. Additionally, the high robustness of the active-particle group at the critical density under the influence of different perturbations is quantitatively validated. These findings support the effectiveness of velocity alignment in real perturbed environments, thereby providing a versatile platform for fundamental studies on collective motion and the development of innovative swarm microrobotics.
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Affiliation(s)
- Zhihan Chen
- Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Hongru Ding
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | | | - Jingang Li
- Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Yuebing Zheng
- Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX, 78712, USA
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
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Alston H, Cocconi L, Bertrand T. Irreversibility across a Nonreciprocal PT-Symmetry-Breaking Phase Transition. PHYSICAL REVIEW LETTERS 2023; 131:258301. [PMID: 38181344 DOI: 10.1103/physrevlett.131.258301] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 10/30/2023] [Indexed: 01/07/2024]
Abstract
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.
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Affiliation(s)
- Henry Alston
- Department of Mathematics, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - Luca Cocconi
- Department of Mathematics, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
- The Francis Crick Institute, London NW1 1AT, United Kingdom
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany
| | - Thibault Bertrand
- Department of Mathematics, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
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Loos SAM, Klapp SHL, Martynec T. Long-Range Order and Directional Defect Propagation in the Nonreciprocal XY Model with Vision Cone Interactions. PHYSICAL REVIEW LETTERS 2023; 130:198301. [PMID: 37243650 DOI: 10.1103/physrevlett.130.198301] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 12/01/2022] [Accepted: 04/11/2023] [Indexed: 05/29/2023]
Abstract
We study a two-dimensional, nonreciprocal XY model, where each spin interacts only with its nearest neighbors in a certain angle around its current orientation, i.e., its "vision cone." Using energetic arguments and Monte Carlo simulations, we show that a true long-range ordered phase emerges. A necessary ingredient is a configuration-dependent bond dilution entailed by the vision cones. Strikingly, defects propagate in a directional manner, thereby breaking the parity and time-reversal symmetry of the spin dynamics. This is detectable by a nonzero entropy production rate.
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Affiliation(s)
- Sarah A M Loos
- DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
| | - Sabine H L Klapp
- Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Thomas Martynec
- Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
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Hecht L, Mandal S, Löwen H, Liebchen B. Active Refrigerators Powered by Inertia. PHYSICAL REVIEW LETTERS 2022; 129:178001. [PMID: 36332249 DOI: 10.1103/physrevlett.129.178001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 05/09/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
We present the operational principle for a refrigerator that uses inertial effects in active Brownian particles to locally reduce their (kinetic) temperature by 2 orders of magnitude below the environmental temperature. This principle exploits the peculiar but so-far unknown shape of the phase diagram of inertial active Brownian particles to initiate motility-induced phase separation in the targeted cooling regime only. Remarkably, active refrigerators operate without requiring isolating walls opening the route toward using them to systematically absorb and trap, e.g., toxic substances from the environment.
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Affiliation(s)
- Lukas Hecht
- Institut für Physik kondensierter Materie, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany
| | - Suvendu Mandal
- Institut für Physik kondensierter Materie, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II-Soft Matter, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
| | - Benno Liebchen
- Institut für Physik kondensierter Materie, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany
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Abstract
Out of equilibrium, a lack of reciprocity is the rule rather than the exception. Non-reciprocity occurs, for instance, in active matter1-6, non-equilibrium systems7-9, networks of neurons10,11, social groups with conformist and contrarian members12, directional interface growth phenomena13-15 and metamaterials16-20. Although wave propagation in non-reciprocal media has recently been closely studied1,16-20, less is known about the consequences of non-reciprocity on the collective behaviour of many-body systems. Here we show that non-reciprocity leads to time-dependent phases in which spontaneously broken continuous symmetries are dynamically restored. We illustrate this mechanism with simple robotic demonstrations. The resulting phase transitions are controlled by spectral singularities called exceptional points21. We describe the emergence of these phases using insights from bifurcation theory22,23 and non-Hermitian quantum mechanics24,25. Our approach captures non-reciprocal generalizations of three archetypal classes of self-organization out of equilibrium: synchronization, flocking and pattern formation. Collective phenomena in these systems range from active time-(quasi)crystals to exceptional-point-enforced pattern formation and hysteresis. Our work lays the foundation for a general theory of critical phenomena in systems whose dynamics is not governed by an optimization principle.
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You Z, Baskaran A, Marchetti MC. Nonreciprocity as a generic route to traveling states. Proc Natl Acad Sci U S A 2020; 117:19767-19772. [PMID: 32753380 PMCID: PMC7444273 DOI: 10.1073/pnas.2010318117] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We examine a nonreciprocally coupled dynamical model of a mixture of two diffusing species. We demonstrate that nonreciprocity, which is encoded in the model via antagonistic cross-diffusivities, provides a generic mechanism for the emergence of traveling patterns in purely diffusive systems with conservative dynamics. In the absence of nonreciprocity, the binary fluid mixture undergoes a phase transition from a homogeneous mixed state to a demixed state with spatially separated regions rich in one of the two components. Above a critical value of the parameter tuning nonreciprocity, the static demixed pattern acquires a finite velocity, resulting in a state that breaks both spatial and time-reversal symmetry, as well as the reflection parity of the static pattern. We elucidate the generic nature of the transition to traveling patterns using a minimal model that can be studied analytically. Our work has direct relevance to nonequilibrium assembly in mixtures of chemically interacting colloids that are known to exhibit nonreciprocal effective interactions, as well as to mixtures of active and passive agents where traveling states of the type predicted here have been observed in simulations. It also provides insight on transitions to traveling and oscillatory states seen in a broad range of nonreciprocal systems with nonconservative dynamics, from reaction-diffusion and prey-predators models to multispecies mixtures of microorganisms with antagonistic interactions.
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Affiliation(s)
- Zhihong You
- Department of Physics, University of California, Santa Barbara, CA 93106;
| | - Aparna Baskaran
- Martin Fisher School of Physics, Brandeis University, Waltham, MA 02453
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Lavergne FA, Wendehenne H, Bäuerle T, Bechinger C. Group formation and cohesion of active particles with visual perception-dependent motility. Science 2019; 364:70-74. [PMID: 30948548 DOI: 10.1126/science.aau5347] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 03/12/2019] [Indexed: 12/29/2022]
Abstract
Group formation in living systems typically results from a delicate balance of repulsive, aligning, and attractive interactions. We found that a mere motility change of the individuals in response to the visual perception of their peers induces group formation and cohesion. We tested this principle in a real system of active particles whose motilities are controlled by an external feedback loop. For narrow fields of view, individuals gathered into cohesive nonpolarized groups without requiring active reorientations. For wider fields of view, cohesion could be achieved by lowering the response threshold. We expect this motility-induced cohesion mechanism to be relevant not only for the self-organization of living systems, but also for the design of robust and scalable autonomous systems.
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Affiliation(s)
| | - Hugo Wendehenne
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany
| | - Tobias Bäuerle
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany
| | - Clemens Bechinger
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany.
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Kliushnychenko OV, Lukyanets SP. Effects of collectively induced scattering of gas stream by impurity ensembles: Shock-wave enhancement and disorder-stimulated nonlinear screening. Phys Rev E 2018; 98:020101. [PMID: 30253471 DOI: 10.1103/physreve.98.020101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Indexed: 06/08/2023]
Abstract
We report on specific effects of collective scattering for a cloud of heavy impurities exposed to a gas stream. Formation is presented of a common density perturbation and shock waves, both generated collectively by a system of scatterers at sudden application of the stream-inducing external field. Our results demonstrate that (i) the scattering of gas stream can be essentially amplified, due to nonlinear collective effects, upon fragmentation of a solid obstacle into a cluster of impurities (heterogeneously fractured obstacle); (ii) a cluster of disordered impurities can produce considerably stronger scattering accompanied by enhanced and accelerated shock wave, as compared to a regularly ordered cluster. We also show that the final steady-state density distribution is formed as a residual perturbation left after the shock front passage. In particular, a kinklike steady distribution profile can be formed as a result of shock front stopping effect. The possibility of the onset of solitary diffusive density waves, reminiscent of precursor solitons, is shown and briefly discussed.
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Affiliation(s)
- O V Kliushnychenko
- Institute of Physics, NAS of Ukraine, Prospect Nauky 46, 03028 Kiev, Ukraine
| | - S P Lukyanets
- Institute of Physics, NAS of Ukraine, Prospect Nauky 46, 03028 Kiev, Ukraine
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