6,443 research outputs found
A Design Path for Hierarchical Self-Assembly of Patchy Colloids
Patchy colloids are promising candidates for building blocks in directed
self-assembly. To be successful the surface patterns need to both be simple
enough to be synthesized, while feature-rich enough to cause the colloids to
self-assemble into desired structures. Achieving this is a challenge for
traditional synthesis methods. Recently it has been suggested that the surface
pattern themselves can be made to self-assemble. In this paper we show that a
wide range of functional structures can be made to self-assemble using this
approach. More generally we present a design path for hierarchical targeted
self-assembly of patchy colloids. At the level of the surface structure, we use
a predictive method utilizing universality of patterns of stripes and spots,
coupled with stoichiometric constraints, to cause highly specific and
functional patterns to self-assemble on spherical surfaces. We use a
minimalistic model of an alkanethiol on gold as a model system and demonstrate
that, even with limited control over the interaction between surface
constituents, we can obtain patterns that causes the colloids themselves to
self-assemble into various complex geometric structures. We demonstrate how
variations of the same design path cause in-silico self-assembly of strings,
membranes, cubic and spherical aggregates, as well as various crystalline
patterns.Comment: 8 pages, 5 figure
Self-assembly mechanism in colloids: perspectives from Statistical Physics
Motivated by recent experimental findings in chemical synthesis of colloidal
particles, we draw an analogy between self-assembly processes occurring in
biological systems (e.g. protein folding) and a new exciting possibility in the
field of material science. We consider a self-assembly process whose elementary
building blocks are decorated patchy colloids of various types, that
spontaneously drive the system toward a unique and predetermined targeted
macroscopic structure.
To this aim, we discuss a simple theoretical model -- the Kern-Frenkel model
-- describing a fluid of colloidal spherical particles with a pre-defined
number and distribution of solvophobic and solvophilic regions on their
surface. The solvophobic and solvophilic regions are described via a
short-range square-well and a hard-sphere potentials, respectively.
Integral equation and perturbation theories are presented to discuss
structural and thermodynamical properties, with particular emphasis on the
computation of the fluid-fluid (or gas-liquid) transition in the
temperature-density plane.
The model allows the description of both one and two attractive caps, as a
function of the fraction of covered attractive surface, thus interpolating
between a square-well and a hard-sphere fluid, upon changing the coverage.
By comparison with Monte Carlo simulations, we assess the pros and the cons
of both integral equation and perturbation theories in the present context of
patchy colloids, where the computational effort for numerical simulations is
rather demanding.Comment: 14 pages, 7 figures, Special issue for the SigmaPhi2011 conferenc
Dimensionality and design of isotropic interactions that stabilize honeycomb, square, simple cubic, and diamond lattices
We use inverse methods of statistical mechanics and computer simulations to
investigate whether an isotropic interaction designed to stabilize a given
two-dimensional (2D) lattice will also favor an analogous three-dimensional
(3D) structure, and vice versa. Specifically, we determine the 3D ordered
lattices favored by isotropic potentials optimized to exhibit stable 2D
honeycomb (or square) periodic structures, as well as the 2D ordered structures
favored by isotropic interactions designed to stabilize 3D diamond (or simple
cubic) lattices. We find a remarkable `transferability' of isotropic potentials
designed to stabilize analogous morphologies in 2D and 3D, irrespective of the
exact interaction form, and we discuss the basis of this cross-dimensional
behavior. Our results suggest that the discovery of interactions that drive
assembly into certain 3D periodic structures of interest can be assisted by
less computationally intensive optimizations targeting the analogous 2D
lattices.Comment: 22 pages (preprint version; includes supplementary information), 5
figures, 3 table
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