Atomic Force Microscope Part 1

Atomic Force Microscope

Seemingly ugly, the black and white logo of IBM is a symbol of nanotechnology’s sophistication over the years. The lines in the logo are actually 5-base-long strands of DNA (Deoxyribose nucleic acid). Before we ponder over IBM’s obsession with making their logos using DNA’s and atoms, let’s discuss how IBM has achieved the once implausible task. A magical result until the underlying science is revealed; the scientific technology employed to get this thing done is atomic force microscopy. The goal of this article is introducing you to the amazing technology, atomic force microscopy.

In a conventional microscope, bending of light is employed to see the microscopic objects. This bending of light is achieved by lenses arranged in a particular fashion. The same technology is used in telescopes as well. Atomic force microscope, against all your intuition, doesn’t work by the same mechanism. As the name implies the microscope works based on atoms and the forces exerted by them. Atomic force microscope is generally used for detection of atoms, molecules or nano-particles on a surface and it can also be used to estimate the size of the nano-particles or configuring atoms or molecules on the surface.

The phrase ‘atoms and forces exerted’ just tells about the basic physics of it but not the way in which the properties of atoms are used to make a microscope. Construction of an atomic force microscope involves a cantilever which has a detecting tip attached to it. The tip is so small that it can detect single atom on a surface. Now if you are trying to think of how small the tip is, it is at times the size of a single atom. And we have learnt during our Physics tuition classes that an atom’s diameter is of the order 10-10 m. This tip scans the surface and whenever it comes near an atom, the tip gets attracted or repelled to it due to inter-atomic forces or atom-ion forces. This attraction or repulsion moves the tip and deflects it from its mean position.

As its mentioned earlier, the tip is attached to a cantilever and whenever the tip moves it is associated with the motion of the cantilever. Although the forces that induce the motion of the tip are of very high intensity, the change in cantilever’s position is very small. Detection of this minute change in the position is a challenge. Let’s discuss about the technology used to detect this tiny motion in the next article.