“Beauty of science is everywhere around us” – I was caught saying this phrase recently; and I wanted to share more of this beauty with everyone. This time I decided to look at the curious phenomena of what happens when you cut a piece of plastic film; but with a blunt object. Say you decide to open that CD case you just bought (who buys CD’s still – but please, just go with my story). You opened it in a with your key chain or your ball point pen and threw that piece of plastic covering.

Pick it up and look at the edge.



Wow – the edge of freshly cut or torn piece of plastic is actually a fractal structure. The edge is ruffled up in many curvy lines (to me, it looks like a cauliflower leaf edge). Look closely; put it in a foldscope; and you will find that the same pattern is repeated also at the microscale. So it is a true fractal (to a certain magnification); so when you see up close, you see the same pattern repeat as before. Isn’t that funny.

Here are some images of the fractal pttern using a foldscope. It turns out; the reason leaves edges have these fractal pattern is not that far from why a torn piece of thin plastic will also have these patterns. The physics of formation of these wrinkles is not that far from the biology of folding of a leaf edge.

Try this yourself; you will be surprised.

Surprisingly, I was also able to image the stress pattern in a stretched piece of plastic. It forms a beautiful ladder network – this one I really need to think hard about. It seems like the stretching of a piece of plastic is never uniform; and it leads to this ladder network. Now I a really puzzled – what gives rise to this ladder network. I don’t think anyone knows the answer as yet. Can you find out?

Read more about – “Buckling Cascades in free sheets, Sharon et al. Nature 2002”
http://www.pmmh.espci.fr/~benoit/publi/nature.pdf

Cheers

Manu