Evolutionary nanotechnology — top down design

Evolutionary nanotechnology involves scaling existing technologies down in size to the nano-scale. This engineering approach is most important with silicon chip technology. Smaller-scale components allow designers to pack more circuitry into a smaller area of silicon, and this has big advantages in terms of processing speed and memory capacity. When we want more in a smaller package, component size must be reduced, and this increasingly involves working with components at the nano-scale.

As an example we can look at the change in size from the original hard drives developed by IBM in the 1970's (which stored 5Mb on a stack of fifty 24-inch diameter discs) to the tiny hard disc drives in modern MP3 players like the iPod (which can store up to 80Gb on a single disc less than one inch in diameter!). If we look more closely, however, we see that this apparent continuum of device scale actually conceals important step changes in technology...

To get more data onto a magnetic disc we have to make the size of the magnetic 'ones and noughts' smaller. These are stored as magnetised patches on the disc surface, but as they get smaller they produce a weaker magnetic field. This means that the detector must be more sensitive to pick up the data.

'Giant Magneto Resistance' (GMR) is the most recent development in this technology. In a read head working on GMR principles, two magnetic layers are separated by a non-magnetic spacer layer a few nm wide. The technology allowed IBM to achieve a world record data density of 35 billion bits per square inch in 1999 - but it is now almost certainly working in a hard drive near you!

While GMR makes positive use of a nanoscale effect, it is more common to encounter problems when trying to make 'big world' devices smaller. One of these problems is the quantum mechanical 'tunnelling' effect. With smaller, and more sensitive devices, electrons are able to 'tunnel' across narrow insulating gaps, and cause spurious signals, which can lead to errors in digital circuits.

Chip manufacturers are working on a range of possible techniques for circumventing this problem, but scientist believe that chip architectures of 4nm may be possible.

The bio-silicon interface

Silicon microcircuitry technology has led to a number of important bioscience advances, with 'gene chips' being perhaps the most influential. While gene chips are not currently nano-scale devices, they are rapidly heading in that direction as manufacturers pack more analytical capacity onto each chip.

With the development of nano-scale chip architectures it will be possible to build devices that have direct interactions with cellular machinery. For the moment, however, this is still largely the domain of radical nanotechnology.

Return to: Nanotechnology timeline.