New and exotic self-organized patterns for modulated nanoscale systems

Surface patterning of low-dimensional systems: the chirality of charged fibres

Charged surfaces are interesting for their ability to have long-range correlations and their ability to be dynamically tuned. While the configurations of charged planar surfaces have been thoroughly mapped and studied, charged cylindrical surfaces show novel features. The surface patterning of cylindrically confined charges is discussed with emphasis on the role of chiral configurations. The origins of surface patterns due to competing interactions in charged monolayers are summarized along with their associated theoretical models. The electrostatically induced patterns described in this paper are important in many low-dimensional biological systems such as plasma membrane organization, filamentous virus capsid structure or microtubule interactions. A simple model effectively predicting some features of chiral patterns in biological systems is presented. We extend our model from helical lamellar patterns to elliptical patterns to consider asymmetrical patterns in assemblies of filamentous aggregates.

Kinetic Pathways of Phase Ordering in Lipid Raft Model Systems

We studied kinetic pathways of order-order transitions in bilayer lipid mixtures using a time-dependent Ginzburg-Landau (TDGL) approach. During the stripe-to-hexagonal phase transition in an incompressible two-component system, the stripe phase first develops a pearl-like instability along the phase boundaries, which grows and drives the stripes to break up into droplets that arrange into a hexagonal pattern. These dynamic features are consistent with recent experimental observations. During the disorder-to-hexagonal phase transition in an incompressible three-component system, the disordered state first passes through a transient stripelike structure, which eventually breaks up into a hexagonal droplet phase. Our results suggest experiments with synthetic vesicles where the stripelike patterns could be observed.

Self-assembled patterns and strain-induced instabilities for modulated systems

The self-assembled domain patterns of modulated systems are characteristic of a wide variety of chemical and physical systems, and are the result of competing interactions. From a technological point of view, there is considerable interest in these domain patterns, as they form suitable templates for the fabrication of nanostructures. We have analyzed the domains and instabilities that form in modulated systems, and show that a large variety of patterns--based on long-lived metastable or glassy states--may be formed as a compromise between the required equilibrium modulation period and the strain present in the system. The strain results from topologically constrained trajectories in phase space, that effectively preclude the equilibrium configuration.