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M13 phage are a novel microrheological probe that are sensitive to polymer relaxations, capturing DNA dynamics and revealing universal scaling behaviors across the unentangled and entangled regimes. 

AbstractColloidal dispersions exhibit rich equilibrium and nonequilibrium thermodynamic properties, self-assemble into diverse structures at different length scales, and display transport behavior under bulk conditions. In confinement or under geometrical restrictions, new phenomena emerge that have no counterpart when the colloids are embedded in an open, noncurved space. In this review, we focus on the effects of confinement and geometry on the self-assembly and transport of colloids and fluidized granular systems, which serve as model systems. Our goal is to summarize experiments, theoretical approximations and molecular simulations that provide physical insight on the role played by the geometry at the mesoscopic scale. We highlight particular challenges, and show preliminary results based on the covariant Smoluchowski equation, that present promising avenues to study colloidal dynamics in a non-Euclidean geometry. 

Escherichia coli expresses surface appendages including fimbriae, flagella, and curli, at various levels in response to environmental conditions and external stimuli. Previous studies have revealed an interplay between expression of fimbriae and flagella in several E. coli strains, but how this regulation between fimbrial and flagellar expression affects adhesion to interfaces is incompletely understood. Here, we investigate how the concurrent expression of fimbriae and flagella by engineered strains of E. coli MG1655 affects their adhesion at liquid–solid and liquid–liquid interfaces. We tune fimbrial and flagellar expression on the cell surface through plasmid-based inducible expression of the fim operon and fliC-flhDC genes. We show that increased fimbrial expression increases interfacial adhesion as well as bacteria-driven actuation of micron-sized objects. Co-expression of flagella in fimbriated bacteria, however, does not greatly affect either of these properties. Together, these results suggest that interfacial adhesion as well as motion actuated by adherent bacteria can be altered by controlling the expression of surface appendages. 

A fundamental assumption of the classical theories of crystal nucleation is that the individual molecules from the “old” phase associate to an emerging nucleus individually and sequentially. 

Spatial heterogeneity in the local strength of attraction with a porous medium influences particle transport under quiescent and flow conditions. 

We investigate the dynamics of polymers grafted to spherical nanoparticles in solution using hybrid molecular dynamics simulations with a coarse-grained solvent modeled via the multiparticle collision dynamics algorithm. The mean-square displacements of monomers near the surface of the nanoparticle exhibit a plateau on intermediate time scales, indicating confined dynamics reminiscent of those reported in neutron spin–echo experiments. The confined dynamics vanish beyond a specific radial distance from the nanoparticle surface that depends on the polymer grafting density. We show that this dynamical confinement transition follows theoretical predictions for the critical distance associated with the structural transition from confined to semidilute brush regimes. These findings suggest the existence of a hitherto unreported dynamic length scale connected with theoretically predicted static fluctuations in spherical polymer brushes and provide new insights into recent experimental observations.