Friday, December 23, 2005

nanomechanics and Prof. John Pethica

Mechanics although sounds mechanical but its starts from the chemistry of atoms and you have mechanics when two atoms comes close to each other. This is how Prof. John Pethica looked at mechanics. Prof. Pethica is a big name in the field of contact mechanics and became quite popular in the campus. His cv is all over the web and I don’t want to write it here.
When two bodies come close to each other there are attractions and repulsion which act on them, and probably this is the first time I saw somebody really, experimentally showing the typical energy plot that we find in all basic material science book Prof Pethica and his group has done it using AFM. He explained the mechanism which drives an atomic force microscope to read the atoms. The striking technology is in the resolution. A laser goes through the tip and reflects back and by detecting the multiple reflections that is coming back, through which it was possible to achieve atomic level resolution in AFM. The probe for AFM can be used as a tool for striking the antom and calculating bond strength between the atoms. So you can literally feel the chemistry of the atoms. It’s really fascinating. So Prof. Pethica’s group in Dublin is working with some technique, developed most probably by them, which is called modulated amplitude AFM technique, this is very effective in measuring the single tip surface bond, the mechanism is bit complicated but it has responses coming in femto seconds and there are advantages over the other tips used for this purpose. After mesmerizing the audience with his measurements in the atomic scale he shifted to some interesting studies on molecules. No, it’s not the big organic molecule, it is water molecule. When the water molecules are kept in between two plates with sufficiently closer (less than nanometer) you start seeing some changes such as viscosity and those change are because of the contacts between the water molecule and the surface. It’s an interesting study from the point of view of biologist as inside a cell the length scale in which water molecules sits is almost similar in order. Prof. Pethica, at the end of his lecture showed few slides of the nano science building at the heart of the town in Dublin. He really wanted to convey the importance of the nano science and technology, but I had a feeling that he has reached beyond that!

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