Design principles for self assembly with short ranged interactions
directed self-assembly, functionalised particles, colloidal clusters, random energy model
Self-assembly is an attractive bottom-up method for fabricating micro-structures which is free of the complexity and cost of traditional top-down approaches such as microfabrication. However, at its current stage of development, it suffers from low yield. In order to direct the formation of pre-designed structures with self-assembly, the constituent particles are frequently functionalised (by means of DNA coating, for example), so that their interactions can be controlled. Previous work on the design criteria for these interactions was based on local particle properties, such as the short-range interaction strength. While these criteria are important, the authors claim that global thermodynamic quantities need also be considered in order to design systems with high yield.
The authors describe their model in terms of a system with constituent particles labeled with two types of labels: geometric labels, which denote the resulting pattern, and energetic labels, which denote the interaction energy between a particle and its neighbors. These concepts are illustrated schematically in figure 1, where the numbers denote the geometrical label and the colors denote the energetic label. Note that in both cases a checkerboard pattern is created, however the energy landscape across the two patterns is different.
As an example of a desired structure, the authors have chosen a