Bridging Scale, Nanotechnology

Dave Smith

CE 252

Nanotechnology and Multi-Scale Simulations

In the past couple of decades, the technology available has increased exponentially. We are able to examine and solve problems now that were only a dream to many scientists 20-25 years ago. As we increase our ability to discover and expand we are also facing new problems every day. These problems come as we delve further into the microscopic and atomistic world. We know how many materials act on the macro scale and we can model different simulations because of that knowledge. As we get into the micro scale and attempt to discover the actions of the atoms as they act with each other we have difficulty simulating the results. This is where the study of Harold S Park helps. It is a study about bridging multi scales for the discovery of how nano wires act and other atomistic applications. The bridging scale couples finite element simulations with molecular dynamic simulations and puts it into two dimensions. The paper takes the reader through a mathematical derivation and two separate problems, one involving wave propagation and one involving dynamic crack propagation. Both of these problems are analyzed mathematically and visually. The point of this study is to create a scale between the atomistic and continuum simulations. Another simulation that Harold talked about during his presentation was the simulation of a gold nanowire and how its atoms acted as a force was placed upon the wire. The wire was attached at one end and it was pulled at the other. As the wire was stretched it reached a point when the atoms in the wire aligned themselves and then finally snapped into two pieces. The amazing thing about the nano-wire was that it was actually stronger than a large hand held macro-scaled gold wire. It is in this technology that major advances in will be reached in the upcoming years.

According to Moore's Law, if the technology used today is not transferred to the molecular level by the year 2015, then we are very behind. The computer companies are very interested in nanotechnology because it will enable them to create whole computers and such on the molecular level, leaving the rest of the actual machine to be designed any way the consumer would like. This technology involves the specific alignment of atoms to create a machine. This is counter to the normal design of machines, where a large machine makes a smaller one, and so on down the line. This requires the atoms to be placed and then systems of atoms can be used to create a machine or operator. Another aspect of nanotechnology of concern and interest is the self-replicating of atoms, or of molecular machines. This idea is similar to all of the atoms making up a tree; the atoms make up cells, which then self replicate and then join together to form the whole tree. These self-replicating molecules are essentially miniature manufacturing plants. They have something to build on the molecular level, something the eye