Tuesday, October 27, 2009

Comment on the size of beads

Chuang and I have tried many different sizes of beads in the construction of beaded structures. From the local of stores in the Taipei area, we can find beads with sizes ranging from 3mm to 20mm. At the beginning, I made a lot of C60, T120, T240, and other toroidal carbon nanotubes with 4mm beads. These beads are quite small and the size of hole is even smaller. It is not easy to do weaving. The resulting structures are small too and look cheap to me. Since the effort to make a beaded molecule is basically quite independent of sizes, at least for beads ranging from 4mm up to 8mm, we decided to do at least with 6mm beads after about a year of playing with 4mm beads. So now most of our large beaded models were made with 6mm beads.

Here is one of early C60 made of 25mm transparent plastic beads (looks like crystal). To make the structure stable, we have to use very thick fishing line. To make a beaded model with beads of this size is quite different from those models with smaller beads (less than 10mm). The friction between the beads and fishing line seem to be too small to hold the structure together. The gravitation of beads become important at this size. So the final structure does not look like being holding by the string only.


Chuang had also made a T120 using the same size of beads. This model is big. Chuang used it as a pillow when he stayed in the lab late at night without going back to his apartment. Unfortunately, the structure is in fact not that robust and it breaked up in a few days before we had a chance to take a picture.

If we want to make structures with even larger beads, it is hard to find commercial beads. We came up with the idea of using Ping-Pong balls. And indeed we bought a lot of Ping-Pong enough for making at least a C60 and a T120. Unfortunately, after we punctured holes on many Ping-Pong balls, we found that it is a non-trivial task to string through these balls. So we didn't have any beaded structures made from Ping-Pong balls. Now we still have many Ping-Pong balls in the lab.

In additional to spherical beads we used usually, we have also tried beads with long aspect ratio. Beaded molecules created by spherical beads usually have much better stability since they effectively mimic the sp2 repulsion. But the disadvantage of spherical beads is that they don't look like the typical chemical bonds we have in mind, i.e. a long stick. Usually, spherical shape is reserved for atoms.
I have found several kind of beads with long aspect ratio at the local stores in Taipei city. The length along longer axis can be as long as 20mm sometimes.


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