Technologists will have to come up with new ways to build the faster and more powerful computers of the future, according to American scientists.

This is because the smallest possible size of electronic component that can be crammed onto silicon computer chips will soon be reached.

There is an unofficial, but remarkably accurate, law in computers - Moore's Law. It states that every few years computer chips will get smaller and more powerful. Specifically, it says that every three years the amount of data that can be packed onto a chip will quadruple.

Chips may need biological molecules to get smaller

The curious thing about Moore's Law is that although it has been followed since 1960 it shows no sign of breaking down. When you consider the great changes in technology that has occurred in the past 30 years it is remarkable that the law has held so long.

Many have previously predicted the demise of Moore's law, saying that with current technologies it will soon not be possible to make things any smaller. So far scientists and engineers have managed to foil these predictions with ingenuity and new technologies.

But perhaps the end will come all because electronic components smaller than an individual atom cannot be made. A report in Nature shows such that a limit is now in sight.

Five atoms wide

David Muller and colleagues of Bell Laboratories and Lucent Technologies in the US note that the narrowest feature on present-day integrated circuits is the thin layer that forms the basis of so-called "field-effect device structures".

If current miniaturisation trends continue, the projected layer thickness by 2012 will be less than one nanometre - that is just five silicon atoms.

Muller and colleagues say that four silicon atoms is the fundamental lower limit for a useable silicon dioxide gate device and that reaching that limit is just over a decade away.

DNA power

Behind this lies the assumption that we can reach this limit in the next few years. Current silicon gate devices have about 25 atoms thickness. So given what we have achieved so far, getting to a few atoms thickness in a few years seems reasonable.

But perhaps in the drive to build faster, more powerful and smaller computers we will turn to biological molecules and harness the power of DNA rather than try to push electrons along arcades of silicon atoms.

Perhaps the computers of the second decade of the next century will have partly living components and perhaps Moore's law will carry on.