ABSTRACT
Self-assembly is fundamentally different from conventional robotic assembly techniques in that structures are put together in a parallel fashion, as opposed to the conventional serial operation. It bears a resemblance to a biological growth mechanism, in the sense that finished units emerge as a result of exposing the template to various component mixtures and environmental conditions. A
key strength of self-assembly is its ability to integrate different types of components into one unit. In this area, it can outperform conventional assembly technologies and may represent an avenue to affordable fabrication of hybrid microstructures.Self-assembly processes can be divided into two broad categories, based on the scale of the components that are being assembled. Microscale self-assembly operates with component dimensions of 1−1000 µm, whereas in nanoscale self-assembly the dimensions lie in the 1−1000 nm range. Owing to the difference in component size, the two processes utilize different phenomena to manipulate components.Microscale processes typically rely on shape recognition as a means of homing, and capillary or gravitational forces for docking and securing the assembled parts in place. Such a principle works well for geometric microscale components, typically prepared by microfabrication techniques. Nanoscale processes are quite different, as they handle components of molecular dimensions and rely on electrostatic interactions, molecular affinity, or covalent chemical reactions both for component homing and securing.Molecular assembly on the nanoscale has been studied and utilized by surface scientists for over a century. A good example of “classical” nanoscale self-assembly is the automatic organization of detergent molecules at an oil−water interface. Microscale self-assembly, however, is a much more recent concept. This is because modern-day fabrication methods are required to produce microscale components, as well as microscale assembly templates.
