Simultaneous measurement of the microscopic dynamics and the mesoscopic displacement field in soft systems by speckle imaging

Brownian Motion in a Speckle Light Field: Tunable Anomalous Diffusion and Deterministic Optical Manipulation

The motion of particles in random potentials occurs in several natural phenomena ranging from the mobility of organelles within a biological cell to the diffusion of stars within a galaxy. A Brownian particle moving in the random optical potential associated to a speckle, i.e., a complex interference pattern generated by the scattering of coherent light by a random medium, provides an ideal mesoscopic model system to study such phenomena. Here, we derive a theory for the motion of a Brownian particle in a speckle and, in particular, we identify its universal characteristic timescale levering o…

Temporal and spatial heterogeneity in aging colloids: a mesoscopic model

A coarse-grained model of dense hard sphere colloids building on simple notions of particle mobility and spatial coherence is presented and shown to reproduce results of experiments and simulations for key quantities such as the intermediate scattering function, the particle mean-square displacement and the $χ_{4}$ mobility correlation function. All results are explained by two emerging and interrelated dynamical properties: i) a rate of intermittent events, quakes, which decreases as the inverse of the system age t; ii) a length scale characterizing correlated domains, which increases linearl…

Length scales in Brownian yet non-Gaussian dynamics

According to the classical theory of Brownian motion, the mean squared displacement of diffusing particles evolves linearly with time whereas the distribution of their displacements is Gaussian. However, recent experiments on mesoscopic particle systems have discovered Brownian yet non-Gaussian regimes where diffusion coexists with an exponential tail in the distribution of displacements. Here we show that, contrary to the present theoretical understanding, the length scale $λ$ associated to this exponential distribution does not necessarily scale in a diffusive way. Simulations of Lennard- Jo…

Formation of double glass in binary mixtures of anisotropic particles: Dynamic heterogeneities in rotations and displacements

We study glass behavior in a mixture of elliptic and circular particles in two dimensions at low temperatures using an orientation-dependent Lennard-Jones potential. The ellipses have a mild aspect ratio ($\sim 1.2$) and tend to align at low temperatures, while the circular particles play the role of impurities disturbing the ellipse orientations at a concentration of 20%. These impurities have a size smaller than that of the ellipses and attract them in the homeotropic alignment. As a result, the coordination number around each impurity is mostly five or four in glassy states. We realize doub…

红细胞变形与动力学决定其通过具有确定性侧向位移架构的微流控器件

Deformation and dynamics of erythrocytes govern their traversal through microfluidic devices with a deterministic lateral displacement architecture

本研究通过介观流体动力学模拟，揭示了红细胞在确定性侧向位移微流控器件中的变形与动力学行为，构建了细胞行为模式图并阐明了分选机制，指出基于剪切弹性的红细胞分选需精细调节流动条件。

Granular packs under vertical tapping: structure evolution, grain motion, and dynamical heterogeneities

The compaction dynamics of a granular media subject to a sequence of vertical taps made of fluid pulses is investigated via Molecular Dynamics simulations. Our study focuses on three different levels: macroscopic (volume fraction), mesoscopic (Vorono\"ı volumes, force distributions) and microscopic (grain displacements). We show that the compaction process has many characteristics which are reminiscent of the slow dynamics of glass forming systems, as previously suggested. For instance the mean volume fraction slowly increases in time and approaches a stationary value following a stretched exp…