‘Repair rather than replace’ is an increasingly popular mantra in design. As sustainable thinking is finally taking centre stage around the world, repairing existing materials, designs and constructions is becoming more and more important.

Recent developments have led to a range of self-healing materials. The best established is self-repairing cement, which is derived from a technique developed by the Romans. It makes use of a natural cycle of limestone, where calcium oxides react with water and carbon dioxide fill in cracks.

The current trend in concretes is to use bacteria. These act as a catalyst, effectively growing back damaged parts of the material. Experiments are under way at the University of Bath. Delft University of Technology has also developed a self-healing solution, and other institutions are joining in.

Self-repairing polymers are an exciting group. This video shows a polymer that repairs itself after being sliced. It’s a break-through because until now, self-healing polymers have cheated a little: they’ve always required external influences such as heat, light or chemicals to perform their trick. Now, a breed of polymers is being introduced that repair themselves without external help.

Though researchers are cagey about details, the principle for healing is always the same. At a molecular level, chemical bonds are exchanged in a process called metathesis. One pair of molecules swaps bonds with another.

When this happens throughout the material, the result is a strong connection between the two halves. Equally important to designers is that these bonds are so small they aren’t visible to the human eye.

Now, even metals can self-heal. In a new discovery, MIT researchers found that some metals repair after cracks are pulled at, a surprise find which could lead to some very interesting materials.

The uses are limitless. Aircraft wings, windmill blades, façade panels, smart phones, clothing: self-healing materials can be an advantage everywhere you look. So far, however, the self-healing family doesn’t include glass, though the screen above does have a self-healing polymer top-layer. Self-healing glass is a challenge to manufacturers world-wide!

For more information, have a look at this BBC article. There is technical information in this Nature article. Check out this video to see the self-healing material at work!

 

All images via creative commons.