A widely acknowledged goal of nanotechnology is to build intricate, useful nanoscale structures. What usually goes unstated is how the structures will be specified. Simple structures can be created easily: a crystal is an atomically precise structure that can be created from simple molecules and conditions. But complex nano-products will require some way to deliver large quantities of information to the nanoscale.
A key indicator of a technology's usefulness is how fast it can deliver information. A kilobyte is not very much information—less than a page of text or a thumbnail image. A dialup modem connection can transfer several kilobytes per second. Today's nanoscale manufacturing techniques can transfer at most a few kilobytes per second. This will not be enough to make advanced products—only simple materials or specialized components.
The amount of information needed to specify a product is not directly related to the size of the product. A product containing repetitive structures only needs enough information to specify one of the structures and control the placement of the rest. The amount of information that needs to be delivered also depends on whether the receiving machine must receive an individual instruction for every operation, or whether it can carry out a sequence of operations based on stored instructions. Thus, a primitive fabrication system may require a gigabyte of information to place a million atoms, while a gigabyte may be sufficient to specify a fairly simple kilogram-scale product built with an advanced nanofactory.
There are several ways to deliver information to the nanoscale so as to construct things. Information can either be encoded materially, in a stable pattern of atoms or electrons, or it can be in an ephemeral form such as an electric field, a pattern of light, a beam of charged particles, the position of a scanning probe, or an environmental condition like temperature. The goal of manufacturing is to embody the information, however it is delivered, into a material product. As we will see, different forms of delivery have different advantages and limitations.
This feature essay, by Chris Phoenix, CRN Director of Research, continues here...