Title: Self-assembly from nanoscale to the mesoscale
Description: Creating useful, ordered structures out of disordered components is the essence of engineering. As materials reduce in size, new techniques are required to produce order at ever smaller scales. In self-assembly processes, energy sources such as thermal energy drive the initially disordered components of a system toward a stable, ordered state. The interactions between the components define the result. We may take advantage of scale-independent self-assembly processes to simplify the engineering of complex systems over orders of magnitude of size. In this dissertation, we present three self-assembling systems. In the first, nonmagnetic particles in a magnetic fluid are self-assembled into ordered clusters. The geometry of the external magnetic field determines the cluster's ultimate geometry. The scale is limited by the magnetization of the fluid and the volumina of the particles. Such a system is useful to bioengineering applications, in cases where it is necessary to work with relatively large-scale components in the absence of a hard surface.

In the second system, we present the self assembly of an ordered fibrin lattice guided by a magnetically self-assembled two-dimensional crystal of superparamagnetic microbeads. The process relies on adhesion, linear polymerization and diffusion to extend the ordering from the nanometer scale of the fibrin fiber to the millimeter scale of the crystal. We show by simulation and experiment that the self-assembly process we describe is applicable to more general materials problems, in addition to tissue engineering. Natural systems take advantage of self-assembly processes for life's basic functions. At the nanoscale, specificity is key to attaining the correct result of protein-protein, protein-DNA, or DNA-DNA interactions and assembly. In artificial systems, the length of the matching polymers has been a fundamental limit in achieving correct binding, and yet, in natural systems, long sequences do correctly find their matching pairs. The third system we present is a simple model of interacting, charged polymers. We propose a mechanism by which long, matching sequences can retain specificity. The proposal has implications both for how natural systems work and how to construct artificial DNA-barcode based self-assembly systems.