Back in the early '90s, a clothing brand called Hypercolor exploded in popularity. The clothes had a special thermochromic dye, which meant the fabric would change color at different temperatures. But craze didn't last (partly because washing or drying the clothes at high temperatures would turn Hypercolor articles into boring normal clothes). Today, a new material that responds to heat could make a much bigger impact.
That material is a new polymer developed by researchers at the University of Rochester. The polymer is elastic, which means it can change shape. Unlike a rubber band, if you stretch this stuff it stays stretched out when you let go. But if you apply just a little heat — like human body temperature heat — the polymer “remembers” its original shape and returns to it.
That might just sound like a cute trick but it has some pretty cool implications. For one thing, the stretched polymer has stored elastic energy. That means the polymer can do work when it warms up. According to the researchers, the polymer is capable of lifting a weight 1,000 times the mass of the polymer itself.
So what's actually happening at the molecular level? A polymer is a long-chain molecule that consists of several smaller molecule units that repeat themselves down the chain. When stretched, some of those smaller molecules in this new polymer align themselves with one another, forming what are called crystallites. This stabilizes the new shape of the polymer — it's why the material doesn't return to its original state as soon as you let go.
Heating the polymer breaks down these crystallites, destabilizing the polymer so that it returns to its original shape. The small molecules in the chain return to their original alignment. You can do this to the same polymer several times. The researchers are working on ways to increase the lifespan of the material so that it can be put to practical use.
Those practical uses will likely be focused primarily on the biomedical field. Imagine a wound dressing that goes on loose (because the polymer is in its stretched-out state) and slowly grows tighter as the injured person's body heat causes it to contract. This could allow for a bandage to apply pressure to a wound. Another potential use is for sutures or stitches, which could tighten themselves once they warm up.
In the future, there may be other applications that are less medically focused but still important. Imagine a new fashion line, something that rivals even the beloved Hypercolor. These clothes go on loose, making it easy to put them on. But then they snug up as they respond to your body heat. Never will you have to struggle into that awesome pair of jeans — they'll just slip right on and then conform to your body!
For the time being, the magic jeans of awesomeness will remain a dream. It may be several years before the polymer is ready for commercial use. But it's an exciting development in materials science!