Active fluids such as swarming bacteria and motile colloids exhibit exotic properties different from conventional equilibrium materials. As a peculiar example, spherical tracer immersed inside active shows an enhanced translational diffusion, orders of magnitude stronger than its intrinsic Brownian motion. Here, rather tracers, we investigate the diffusion isolated ellipsoids in quasi-two-dimensional bacterial bath. Our study nonlinear enhancement both rotational diffusions ellipsoids. More...

Colloidal suspensions self-assemble into equilibrium structures ranging from face- and body-centered cubic crystals to binary ionic crystals, even kagome lattices. When driven out of by hydrodynamic interactions, more diverse can be accessed. However, mechanisms underlying out-of-equilibrium assembly are much less understood, though such processes clearly relevant in many natural industrial systems. Even the simple case hard-sphere colloidal particles under shear, there conflicting...

Colloidal suspensions exhibit shear thinning and thickening. The most common interpretation of these phenomena identifies layering the fluid perpendicular to gradient as driver for observed behavior. However, studies particle configurations associated with thickening cast doubt on that conclusion leave unsettled whether nonequilibrium are caused primarily by correlated motions or changes in packing structure. We report results Stokesian dynamics simulations hard spheres illuminate relation...

Significance Bacterial suspensions can flow without apparent viscosity. Such a superfluid-like behavior stems from the collective motions of swimming bacteria. Here, we explore microscopic profile bacterial “superfluids” under simple shear. We find that, instead deforming uniformly, superfluids develop multiple shear bands, i.e., regions with different deformations. construct model that quantitatively describes shape shear-banding structure and reveals important physical properties motions....

Metamaterials are artificial materials that can achieve unusual properties through unique structures. In particular, their “invisibility” property has attracted enormous attention due to its little or negligible disturbance the background field avoids detection. This invisibility feature is not only useful for optical field, but it also important any manipulation requires minimum background, such as flow inside human body. There several conventional invisible metamaterial designs: a cloak...

Run-and-tumble is a common but vital strategy that bacteria employ to explore environment suffused with boundaries, as well escape from entrapment. In this study we reveal how and the resulting dynamical behavior can be sensitively regulated by bacterial dimensions. Our results demonstrate logarithm of surface residence time for constant tumble bias linearly related dimensionless parameter intrinsic size characteristics, where small variation in dimensions, which natural suspension,...

When placed in flows with local shear, flagellated bacteria commonly display reorientations toward the vorticity direction, a chirality-induced rheotactic behavior of great importance for many biological functions. As observed reorientational dynamics arises from interplay between Jeffery controlled by cell aspect ratio and reorientation chiral strength, this work we quantitatively study how can become key factor tuning dynamics, through numerical theoretical analyses. Our results reveal...

Bio-inspired reversible adhesives have attracted great attention because of their promising applications in the electronic, biomedical, and robotic fields. Here, to achieve situ adhesion, a new concept is demonstrated by modulating conformations polydimethylsiloxane (PDMS) chains. The adhesive, termed BGPP, composed graphene/PDMS composite (GP) as backing layer PDMS micropillar array. photothermal effect graphene under UV irradiation heats up micropillars, resulting an increase chain thus...

Enhanced diffusion of passive tracers immersed in active fluids is a universal feature and has been extensively studied recent years. Similar to microrheology for equilibrium complex fluids, the unusual enhanced particle dynamics reveal intrinsic properties fluids. Nevertheless, previous studies have shown that translational spherical are qualitatively similar, independent whether particles pushers or pullers---the two fundamental classes Is it possible distinguish from pullers by simply...

We report the results of experimental studies short-time--long-wavelength behavior collective particle displacements in quasi-one-dimensional (q1D) and quasi-two-dimensional (q2D) colloid suspensions. Our are reported via $q\ensuremath{\rightarrow}0$ hydrodynamic function $H$($q$) that relates effective diffusion coefficient ${D}_{e}$($q$), with static structure factor $S$($q$) self-diffusion isolated particles ${D}_{0}$:...

We report a study of DNA deformations using coarse-grained mechanical model and quantitatively interpret the allosteric effects in protein-DNA binding affinity. A recent single-molecule (Kim et al. Science 2013, 339, 816) showed that when molecule is deformed by specific protein, affinity second protein separated from first altered. Experimental observations together with molecular dynamics simulations suggested origin allostery related to observed deformation DNA's structure, particular,...

We report an analysis of the thickness dependence liquid-to-hexatic phase transition in a quasi-two-dimensional hard-sphere colloid system as confining wall separation changes from 1 to 1.6 diameters. In our theoretical evaluation, we study bifurcation solutions integral equation for pair correlation function. Our predicts that at small is continuous and it occurs lower density than liquid-to-crystal density, agreement with predictions strictly two-dimensional obtained...

We report calculations of the density maximally random jamming one-component and binary hard-disk fluids. The theoretical structure used provides a common framework for description liquid-to-hexatic, liquid-to-hexagonal crystal, liquid to jammed state transitions. Our analysis is based on locating particular bifurcation solutions integral equation inhomogeneous single-particle at transition between different spatial structures. we study initiated from dense metastable fluid, associate it...

The effect of hydrodynamic interaction on the separation dependence center mass and relative pair diffusion coefficients colloid particles in a quasi-one-dimensional system, including influence proximate walls, is calculated using method reflections. There excellent agreement between theoretical predictions experimental data. We show that coefficient has an oscillatory structure scale length correlation we directly relate to function system.

Mechanical characteristics of DNA in the sub-persistence-length (lP ≈ 150 base pairs) regime are vital to many its biological functions but not well understood. Recent experimental studies this have shown a dramatic departure from traditional worm-like chain model, which is designed for long chains and predicts constant flexibility at all length scales. Here, we report an improved model with explicit considerations new scale lD 10 pairs, over local bend angles correlated. In correlated...

Significance Active suspensions of microswimmers demonstrate novel emergent behaviors (self-organizations, active turbulence, etc.) on macroscopic length scales. For such systems with, minimally, thousands microswimmers, direct numerical simulations the hydrodynamic interactions are computationally infeasible, and reduced models needed. We demonstrated that existing not satisfactory in describing for close proximity with even qualitatively erroneous predictions, indicating a pressing need an...

The entrapment of bacteria near boundary surfaces is biological and practical importance, yet the underlying physics not well understood. We demonstrate that it crucial to include a commonly neglected thermodynamic effect related spatial variation hydrodynamic interactions, through model provides analytic explanation bacterial in two dimensionless parameters: ${\ensuremath{\alpha}}_{1}$ ratio thermal energy self-propulsion, ${\ensuremath{\alpha}}_{2}$ an intrinsic shape factor. For match...

We investigate the response of a dense monodisperse quasi-two-dimensional (q2D) colloid suspension when particle is dragged by constant velocity optical trap. Consistent with microrheological studies other geometries, perturbation induces leading density wave and trailing wake, we use Stokesian Dynamics (SD) simulations to parse direct colloid-colloid hydrodynamic interactions. go on analyze underlying individual particle-particle collisions in experimental images. The displacements...

The effect of hydrodynamic interactions on the spreading clusters colloid particles in a quasi-one-dimensional channel is analyzed both experimentally and theoretically. An n-particle cluster diffusion coefficient defined, terms displacement Deltax(t) time t, by D(n)[triple bond]<[Sigma(i=1)(n)Deltax(i)(t)](2)>/2nt, where average taken over all groups n adjacent particles. Our study focuses n-dependence D(n) with some attention to dependence packing fraction. We find that ratio infinite...

The properties of a classical simple liquid are strongly affected by the application an external potential that supports inhomogeneity. To understand nature these property changes, equilibrium particle distribution functions have, typically, been calculated directly using either integral equation or density functional based analyses. In this study, we develop different approach with focus on two characterize inhomogeneous liquid: pair direct correlation function c(r1,r2) and g(r1,r2). With...