Rashmi Desai and Raymond Kapral: Dynamics of Self-Organized and Self-Assembled Structures

Abstract

Nature exhibits the remarkable ability to self-organize into a variety of complex dynamic and static architectures when driven far from thermal equilibrium by external forces or by heat and concentration gradients. Self-assembly, an ability to create ordered structures from simpler building blocks can range from single molecules to complex protein assemblies and is one of the most common self-organization processes occurring in a majority of biological and some synthetic systems. Self-assembly is ubiquitous in everyday life—at the most basic level all living organisms are self-assembling entities. Self-assembly is also one of the few practical strategies for large-scale production of nanostructured materials and is therefore an essential part of nanotechnology. While self-assembly can take place on scales as small as the molecular, control of self-assembly is possible largely by the manipulation of macroscopic variables such as temperature, pressure, composition, and applied electric or magnetic fields. Nature routinely exhibits self-assembly. The potential to predict, model, and ultimately tailor the properties of self-assembled materials for broad technological applications, however, has been hampered by the lack of fundamental understanding of the dynamics of selfassembly and the ability to bridge from the microscopic to the macroscopic scales. Although the definitions of self-assembling systems are very broad, it is practical to identify two major classes: static and dynamic. Static self-assembly involves systems that are at global or local equilibrium and do not dissipate energy. For example lipid bilayers and most systems exhibiting spinodal decomposition are formed by static self-assembly. In static selfassembly the formation of ordered structures may require energy, but once they are formed they are stable. In dynamic self-assembly, such as most of the biological systems and autocatalytic chemical reactions, the interactions responsible for the formation of nontrivial structures occurs only if the system is consuming energy from an external energy source provided, for example, by an applied field from chemical reactions. Since the hierarchical