What makes nanotechnology possible?

Nano-scale stuff has always been around us. What is different now is our ability to examine and work with material at this scale with increasing ease. We are able to do this because of a number of technical advances, but perhaps the most influential advance was the development of scanning probe microscopies (SPM) in the 1980's:

The Atomic Force Microscope

The Atomic Force Microscope (AFM) was not the first SPM technique to be invented, but it is the easiest to understand. In essence a very fine probe is used to read a surface. As the probe moves over the surface it encounters lumps and bumps, which cause it to move up and down. This movement is detected by the deflection of a laser beam that is reflected off the back of the probe - as shown right.

In practice this simple system would risk damage to both the probe and the surface being studied. The scanning tip would tend to plough through large bumps, but may not probe to the bottom of deep holes. To get round this the sample is mounted on a piezoelectric stage, which allows the sample to be adjusted up or down by as little as 0.01nm. As the AFM tip rides over the surface, electronics drive the stage to keep the deflection of the laser beam constant - so it stays at the same height throughout the process.

The reason AFM is so important is that it can probe surfaces in air, and even under water. Earlier imaging techniques were restricted to use in hard vacuum - and often samples had to be pre-treated with metallic coatings. AFM techniques have the ability to look at living cellular machinery!

Other techniques important in the development of nanotechnology include:

Electron microscopes: In our journey to the nano-world we found that, limited by the wavelength of visible light, we cannot see objects much smaller that a micrometre. One of the first technologies to overcome this limit was the electron microscope. This uses electrons as opposed to photons to probe matter, and while it has limitations, it is still a very important tool for examining nano-scale structures, as it can examine larger sample areas than is practical with SPM.

Epitaxial techniques: While SPM provides a new window on the nano-world, it is the advance in silicon-based electronic chip technology that drives a lot of the technical development in this field. Current processor architecture resolutions are to better than 45nm - see evolutionary nanotechnology.

Molecular biology: Life was there first - our cells are the archetypal nano-factories. Synthetic DNA has been used to build 'proof of purpose' models for molecular computing , as well as serving as the building blocks in 'molecular mecano'. As our control over organisms at the genetic level improves, simple bacteria may offer a quick leg-up to making nano-devices in bulk - see radical nanotechnology.

Return to: Nanotechnology timeline.