The Changing Shape of Life and Polymers

There are two-fold reasons to celebrate on this somewhat cool, dreary Friday. The first reason, which anyone reading this blog probably already knows since they know me personally, is that it's my birthday.

Exciting!

The second reason is that, according to the Facebook update I just received, today's NPR Science Friday is being broadcast just down the road at the St. Louis Science Center. And for those of you who don't think this is cause for revelry and celebration, find a new blog. You're not nerdy enough for this one.

Because it's my birthday, a day that makes it unquestionably clear that I'm getting older and there's nothing I can do about, I sometimes find myself thinking of bygone days and the many birthdays that have come before. Therefore, I thought I would stick with the theme of 'memory' for this afternoon's post. If you're a neuroscientist (I've got a particular one in mind, but won't mention him by name), then you're probably going to be disappointed. I'm not talking about the biology and function of the brain's capacity to store information. Instead, I'm referring to the shape memory of materials. For the engineers among us, the first word that comes to mind when I say 'shape memory' is most likely Nitinol. Nitinol is a shape memory alloy of nickel and titanium and is commonly used as the scaffold material in angioplasty stents. The stents are designed in such a way that, at room temperature, the Nitinol scaffold constricts and collapses into a small, dense shape. A catheter is then used to place the stent at the location of a blocked blood vessel. Once in place, the Nitinol warms to body temperature and the scaffold expands, opening the blockage and restoring blood flow.

There are other materials that have this same shape memory based on temperature, and there are also other means of restoring some materials to their original shape - such as with magnetic fields or electrical current. Most of these materials have been specifically engineered for this purpose. However, a polymer produced by DuPont with the proprietary name Nafion that has been widely used in fuel cells has recently been added to the list of shape memory materials. According to an article in ScienceNews, Nafion is capable of 'remembering' three previously held shapes through cycles of heating and cooling. Even though materials with such properties are not overtly rare, it is unusual to just stumble upon one, as is the case with Nafion. It just goes to show that there's always more totally rad stuff out there to study, examine, and poke and prod.

And with that, I'm off to celebrate my birthday...and to celebrate being in the same state as Ira Flatow.