Building Methods

There are two general approaches to building structures. These methods are called top-down and bottom-up.


Using top-down methods, researchers selectively modify the starting material much like an artist creates a sculpture from a slab of marble. This method is more traditional in that material is altered (e.g., removed, added to, etc.) by mechanical or chemical means. Photolithography and electron beam lithography are examples of top-down approaches that are used extensively in the semiconductor industry to fabricate integrated electronic circuitry.

Some top-down approaches are already well developed and being commercialized. There are some who believe that there are limits to this method.

Using the bottom-up method, researchers seek to build larger and more complex systems molecule-by-molecule. With this method, molecules are designed and created that have the ability to spontaneously self-assemble when a chemical or physical trigger is applied. Nature routinely uses this method. Although bottom-up processes are less developed and understood, they hold great promise for the future.

At the nanoscale, researchers are working at both ends of the spectrum and these two general approaches are converging.