We study the hydrodynamics of spherical spinners suspended in a Newtonian fluid at inertial regime. We observe a spontaneous condensation of the spinners into particle rich regions, at low but finite particle Reynolds numbers and volume fractions. The particle clusters have a coherent internal dynamics. The spinners form colloidal vortices surrounded by the fluid depleted of the particles. The formation of vortices is observed both in periodic simulation box and when the spinners are confined between two flat walls. The stabilisation of the observed states relies only on hydrodynamic interactions between the spinners and requires a finite amount of inertia. The observations pave the way for the realisation of 3-dimensional spinner materials, where coherent structures and collective dynamics arise only from the rotational motion of the constituents.
We study the dynamics of torque driven spherical spinners settled on a surface, and demonstrate that hydrodynamic interactions at finite Reynolds numbers can lead to a concentration dependent and non-uniform crystallisation. At semi-dilute concentrations, we observe a rapid formation of a uniform hexagonal structure in the spinner monolayer. We attribute this to repulsive hydrodynamic interactions created by the secondary flow of the spinning particles. Increasing the surface coverage leads to a state with two co-existing spinner densities. The uniform hexagonal structure deviates into a high …
Collections of interacting, self-propelled particles have been extensively studied as minimal models of many living and synthetic systems from bird flocks to active colloids. However, the influence of active rotations in the absence of self-propulsion i.e. spinning without walking) remains less explored. Here, we numerically and theoretically investigate the behaviour of ensembles of self-spinning dimers. We find that geometric frustration of dimer rotation by interactions yields spatiotemporal order and active melting with no equilibrium counterparts. At low density, the spinning dimers self-…
Active matter systems are able to exhibit emergent non-equilibrium states due to activity-induced effective interactions between the active particles. Here we study the aggregation and dynamical behavior of active rotating particles, spinners, embedded in 2D passive colloidal monolayers, which constitutes one such non-equilibrium process. Using both experiments and simulations we observe aggregation of active particles or spinners whose behavior resembles classical 2D coarsening. The aggregation behavior and spinner attraction depends on the mechanical properties of the passive monolayer and t…
We investigate collective phenomena with rotationally driven spinners of concave shape. Each spinner experiences a constant internal torque in either a clockwise or counterclockwise direction. Although the spinners are modeled as hard, otherwise non-interacting rigid bodies, we find that their active motion induces an effective interaction that favors rotation in the same direction. With increasing density and activity, phase separation occurs via spinodal decomposition, as well as self-organization into rotating crystals. We observe the emergence of cooperative, super-diffusive motion along i…
Order by inertia in spinning active matter: holey fluids and spin-textured crystals
Univ. Lyon, ENS de Lyon, Univ. Claude Bernard, CNRS, Laboratoire de Physique（里昂大学，里昂高等师范学校，克劳德·贝尔纳大学，法国国家科学研究中心，物理实验室）；Institute of Physics, University of Amsterdam（阿姆斯特丹大学物理研究所）
Phase separation in a chiral active fluid of inertial self-spinning disks
Dipartimento di Fisica, Università degli studi di Bari（巴里大学物理系）；INFN, Sezione di Bari（意大利国家核物理研究所巴里分部）；Universitat de Barcelona Institute of Complex Systems (UBICS)（巴塞罗那大学复杂系统研究所）；Departament de Física de la Matèria Condensada, Universitat de Barcelona（巴塞罗那大学凝聚态物理系）；Universidad de Extremadura（埃斯特雷马杜拉大学）
In many active matter systems, particle trajectories have a well-defined handedness or chirality. Whether such chiral activity can introduce stereoselective interactions between particles is not known. Here we developed a strategy to tune the nature of chiral activity of 3D-printed granular ellipsoids without altering their shape or size. In vertically agitated monolayers of these particles, we observed two types of dimers form depending on the chirality of the pairing monomers. Heterochiral dimers moved collectively as a single achiral active unit, while homochiral ones formed a translational…
Emergent hydrodynamics of chiral active fluids: vortices, bubbles and odd diffusion
School of Sciences and Technology, University of Camerino（卡梅里诺大学科学与技术学院）；Sapienza University of Rome（罗马第一大学）；Paris-Saclay University, CNRS, Laboratoire de Physique des Solides（巴黎萨克雷大学，法国国家科学研究中心，固体物理实验室）
Phase Separation in a system of Brownian inertial rotors
Università degli Studi di Bari（巴里大学）；INFN, Sezione di Bari（意大利国家核物理研究所巴里分部）；CY Cergy Paris Université（塞吉-蓬图瓦兹巴黎大学）；CNRS UMR 8089（法国国家科学研究中心8089联合研究实验室）；Universitat de Barcelona（巴塞罗那大学）
