Building Blocks of Nanocomputing

Can you ever imagine a computer smaller than the width of your hair? Nanotechnology promises on delivering such a computer. In this article, we take a look at the world of nanotechnology, particularly nanocomputing. Nanotechnology deals with the techniques of operating and building at the nanometer scale. One nanometer is equal to one millionth of a millimeter. And nanocomputing deals with computations and computing machinery at the nano-scale level!!!

The obvious question that any computer engineer is going to ask is how do they build a diode, or AND, OR and NOT gates at that level and how do they make the wires for conducting electricity to make these electronic devices work at that level. AND, OR and NOT gates are imperative to building ADDERS and other macro-building blocks of a computer’s central processing unit (CPU). We could also build memory once we have these basic digital logic gates for implementing Boolean logic.

In 1959, Richard Feynman first conceived the idea of arranging things molecule-by-molecule and subsequently atom-by-atom, some day. The US Federal Government funded several breakthrough projects in nanotechnology and as a result we now have machinery to operate and arrange at atomic levels. Figure 1 shows the way atoms are put together one by one, in the shape of a circle to prove this. A high level diagram of the machine used to develop it is shown in figure 2. This machine has the capability to scan atoms so that one can view the atoms and their current positions. It has an ability to repel an atom so as to exert an external force to move an atom away from a specific place; the ability to attract can be leveraged to move an atom to a desired position while the tapping mode provides ability to etch an atom in a specific place. These are the basic operations essential to perform the act of arranging atoms.

Fig 1: Atoms being arranged one by one to form a circle



This concept brings several questions to the fore. How specifically can atoms align themselves to be in a circle as shown? Even if we achieve this alignment, how strong can the nanocomputer be so that it won’t break when someone throws it on the floor?

Well, when we are talking nano, then the floor is not even needed; someone blowing on it can cause agitating tremors. However, materials such as carbon nanotubes that have been designed for this and other purposes (figure 3) are more than 50 times stronger than regular high-carbon steel (used in Industry for cutting metals). And diodes can be formed by joining two nanoscale carbon nanotubes with different electronic properties.

You can now see that not only can we form atoms and molecules in the desired shape, but also have conducting and semi-conducting carbon nanotubes to achieve the required properties.

Phenylene group comprised of C6H4 structures have been shown to produce larger conductive molecules, which integrate molecular wires and molecular switches. The next step is to put together the AND gate using a molecule, which was shown to have the property of a diode.

In figure 4, we can see how an AND gate is usually built with diodes and resistors and providing voltage. Recent research by MITRE Corporation, which is one of the United States Department of Defense’s organization, came up with a molecular electronic AND gate, incorporating polyphenylene-based Molecular Rectifying Diodes embedded in tour wires (figure 5).





Once we have a basic AND gate, OR and NOT gates could be created using similar structures. Digital electronics and computing design principles can help build more complex logic structures utilizing these three basic computing building blocks. Among the things that could be created using these are the CPU (Central Processing Unit), memory (ROM and RAM) and any other device like hard disk, etc. Currently, research is driving the development of storage media using nano elements for storing bits and bytes. A computer built using nano elements as the building blocks of a computer is called a nanocomputer.

In the near future, one can put a factory on a chip manufacturing nanocomputers on nanoconveyers, depicted in figure 6. Tremendous opportunities to work in Physics, Chemistry, Material Science, Biotechnology and Computational Sciences exist now to make this a reality. This article is intended as a computer developer’s peek into understanding the world of Nanocomputers. Eric Drexler popularized the potential of hypothetical ‘Nanotechnology’, a phrase coined by Norio Taniguchi of Japan in 1974. Ralph Mekle and James Ellenbogen are the foremost researchers in this field of nanotechnology.



The steps towards creating a nanocomputer are clearer now. Nanorex, aided by Eric Drexler’s contributions, has developed an Open Source software for developing Computer Aided Designs of nano-machinery. Innovating in the areas of nanogrid development, high-performance parallel and distributed computing, computer architecture and computer engineering can pave the way for breakthroughs in this area.

Acknowledgements:

Figures 1 and 2: These images are courtesy of Popular Mechanics magazine available online at www.popularmechanics.com.
Figure 3: As a work of the U.S. federal government, this image is in the public domain. It is available on Wikipedia.
Figures 4 and 5: Dr. James Ellenbogen permitted and shared this work of MITRE Corporation, a US Department of Defense, for this article.
Figure 6: Image graciously shared by Eric Drexler for this article.

About the Author: Srinivas Polisetty, is currently the Head of the Office of Innovation for Computer Sciences Corporation India. He can be reached on: spolisetty@csc.com. Opinions expressed in this article are his personal ones and not of the organization he represents.