We live in a world full of stuff. It is this manufacture of materials that allows us to clothe ourselves, to build cities and to travel. But so much of human history has been taken up with inventing and making new stuff that we now have rather a lot of it. It fills our homes, our offices, our hospitals. Looking after it all has become somewhat onerous.

Our cars are more reliable, more economical and more comfortable, but they have also become more complicated, so that repairing them requires specialist diagnostic equipment. Similarly, it is beyond most people’s ability to repair their phones when they break. Even manufacturers would rather replace something than mend it. Infrastructure still gets fixed but this, too, is becoming increasingly difficult and expensive.

What is the answer? Should we try to stop the increasing complexity of our material world? Many advocate this, but I am not one of them. My research aims to do the opposite, to help create materials and engineering systems that are complex enough that they can sense when they are damaged, and are able to repair themselves. Is it possible, for example, to have a city where potholes get fixed autonomously, before they become dangerous and expensive? The main drivers of such self-healing technology are economic and environmental, and promise to yield cities that are more like forests, in that they are self-sustaining ecosystems.