Exact solutions for viscous Marangoni spreading.

When surface-active molecules are released at a liquid interface, their spreading dynamics is controlled by Marangoni flows. Though such Marangoni spreading was investigated in different limits, exact solutions remain very few. Here we consider the spreading of an insoluble surfactant along the interface of a deep fluid layer.

Self-propulsion of symmetric chemically active particles: Point-source model and experiments on camphor disks.

Solid undeformable particles surrounded by a liquid medium or interface may propel themselves by altering their local environment. Such nonmechanical swimming is at work in autophoretic swimmers, whose self-generated field gradient induces a slip velocity on their surface, and in interfacial swimmers, which exploit unbalance in surface tension. In both classes of systems, swimmers with intrinsic asymmetry have received the most attention but self-propulsion is also possible for particles that are perfectly isotropic.

Generalized run-and-turn motions: From bacteria to Lévy walks.

Swimming bacteria exhibit a repertoire of motility patterns, in which persistent motion is interrupted by turning events. What are the statistical properties of such random walks? If some particular instances have long been studied, the general case where turning times do not follow a Poisson process has remained unsolved. We present a generic extension of the continuous time random walks formalism relying on operators and noncommutative calculus.

[Optimal permeability of aquaporins: a question of shape?].

Aquaporins are transmembrane proteins, ubiquitous in the human body. Inserted into the cell membranes, they play an important role in filtration, absorption and secretion of fluids. However, the excellent compromise between selectivity and permeability of aquaporins remains elusive.

Anomalous ζ potential in foam films.

Electrokinetic effects offer a method of choice to control flows in micro- and nanofluidic systems. While a rather clear picture of these phenomena exists now for the liquid-solid interfaces, the case of liquid-air interfaces remains largely unexplored. Here, we investigate at the molecular level electrokinetic transport in a liquid film covered with ionic surfactants.

Optimizing water permeability through the hourglass shape of aquaporins.

The ubiquitous aquaporin channels are able to conduct water across cell membranes, combining the seemingly antagonist functions of a very high selectivity with a remarkable permeability. Whereas molecular details are obvious keys to perform these tasks, the overall efficiency of transport in such nanopores is also strongly limited by viscous dissipation arising at the connection between the nanoconstriction and the nearby bulk reservoirs. In this contribution, we focus on these so-called entrance effects and specifically examine whether the characteristic hourglass shape of aquaporins may arise from a geometrical optimum for such hydrodynamic dissipation.

Thermal fluctuations of hydrodynamic flows in nanochannels.

Flows at the nanoscale are subject to thermal fluctuations. In this work, we explore the consequences for a fluid confined within a channel of nanometric size. First, the phenomenon is illustrated on the basis of molecular dynamics simulations.

Thermal fluctuations in nanofluidic transport.

We explore the impact of thermal fluctuations on nanofluidic transport. We develop a generic description of the stochastic motion of a fluid confined in a nanopore, on the basis of the fluctuating hydrodynamics framework. The center of mass of the confined fluid is shown to perform a non-markovian random walk, whose diffusion coefficient depends on the nanopore geometrical characteristics and boundary slip at its surface.

Graphoepitaxial assembly of asymmetric ternary blends of block copolymers and homopolymers.

Ternary blends of cylinder-forming polystyrene-block-poly(methyl methacrylate) block copolymers and polystyrene and poly(methyl methacrylate) homopolymers were assembled in trench features of constant width. Increasing the fraction of homopolymer in the blend increased the spacing and size of block copolymer domains, which were oriented perpendicular to the substrate to form a hexagonal lattice within the trench. The number of rows of cylinders within the trench was controlled by the blend composition.

Simulations of theoretically informed coarse grain models of polymeric systems.

Simulations of theoretically informed coarse grain models, where the interaction energy is given by a functional of the local density, are discussed in the context of polymeric melts. Two different implementations are presented by addressing two examples. The first relies on a grid-based representation of non-bonded interactions and focuses on the concept of density multiplication in block copolymer lithography.

Theoretically informed coarse grain simulations of polymeric systems.

A Monte Carlo formalism for the study of polymeric melts is described. The model is particle-based, but the interaction is derived from a local density functional that appears in the field-based model. The method enables Monte Carlo simulations in the nVT, nPT, semigrandcanonical and Gibbs ensembles, and direct calculation of free energies.

Monte carlo simulation of coarse grain polymeric systems.

We introduce a particle-based Monte Carlo formalism for the study of polymeric melts, where the interaction energy is given by a local density functional, as is done in traditional field-theoretic models. The method enables Monte Carlo simulations in arbitrary ensembles and direct calculation of free energies. We present results for the phase diagram and the critical point of a binary homopolymer blend.

Density multiplication and improved lithography by directed block copolymer assembly.

Self-assembling materials spontaneously form structures at length scales of interest in nanotechnology. In the particular case of block copolymers, the thermodynamic driving forces for self-assembly are small, and low-energy defects can get easily trapped. We directed the assembly of defect-free arrays of isolated block copolymer domains at densities up to 1 terabit per square inch on chemically patterned surfaces.

Hierarchical assembly of nanoparticle superstructures from block copolymer-nanoparticle composites.

We investigate the assembly of block copolymer-nanoparticle composite films on chemically nanopatterned substrates and present fully three-dimensional simulations of a coarse grain model for these hybrid systems. The location and distribution of nanoparticles within the ordered block copolymer domains depends on the thermodynamic state of the composite in equilibrium with the surface. Hierarchical assembly of nanoparticles enables applications in which the ability to precisely control their locations within periodic and nonregular geometry patterns and arrays is required.