Tuesday, November 25, 2008

Our Self Assembled Universe

Often, after a presentation about the exiting developments in nanotechnology, a common question I am asked is "How are things made at the nanoscale?"

This is an insightful question because the person asking it has understood that at the nanoscale, where are working with molecules that are 80,000 times smaller than the diameter of a human hair, the idea of moving and attaching one molecule to another would be a tedious if not impossible task.

Other, more specific questions are:
"Are there nanomachines that build these nanomaterials?"
"How do we position the 60 carbons in a buckyball to get that soccer ball shape?"
"How long does this process take?"

The rather simple answer to these questions is that under certain conditions many molecules just self assemble - they make themselves. This process of self assembly is very fast and is analogous to molecules sticking together. Rather than forming covalent bonds, self assembly exploits weaker bonds (like hydrogen bonding) but because there are many many bonds, these self assembled structures can be very strong. Examples of naturally occurring self assembled structures include the collagen that makes up our bones and hair, DNA that codes our genes, and proteins - the stuff that makes us alive.

Self assembly happens at a very fast pace, at the speed of an electron, and millions of molecules can attach in very specific fashions using simple rules. Yet the result can be very intricate structures (like snowflakes) and new materials like buckyballs. To make buckyballs, we just have to blast carbon monoxide or another carbon source into a furnace that is at the right temperature and pressure for the carbons to take on its soccer ball shape because carbon is obeying some simple thermodynamic rules to minimize its energy. As nanotechnologists, our job is to understand what these rules are and try to create the environmental conditions that will promote nature's ability to build itself. We live in a self assembled universe.

No comments: