Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World

by Mark Miodownik

Our bodies are very picky about materials inserted into them. Most things are rejected, but titanium is one of the few metals they will tolerate. More than that, titanium will undergo osseointegration, which means that it will form strong bonds with living bone.

Aging is the cellular equivalent of playing telephone: each generation of cells does not quite regenerate the structure it inherited and so mistakes and imperfections creep in. My skin has aged not because my skin cells are forty-three years old—they are not; they are constantly being replaced with new cells generated by my adult stem cells—but because, over time, problems and imperfections have developed in the structure of my skin and have then been passed from one generation of cells to the next.

This is the technology that was envisaged in The Six Million Dollar Man, which allowed him to be “Better, Stronger, Faster.” In today’s money, those six million dollars would be thirty-five million dollars, and although this is a fictional figure, it does highlight an important truth about life-extending technologies: they are expensive. The technology that will allow us to lead fit and healthy lives up to the age of a hundred is likely to cost a great deal of money. Who will pay? Will it be a luxury? Will it be only the rich who can play tennis at the age of ninety-eight while the rest of us are in wheelchairs? Or will the technology simply allow us to work longer, making it normal to do so until eighty or ninety? I prefer the latter future, but if thirty-five million dollars is anywhere close to the right figure, then most of us will never be able to afford it, however many years we work.

On Earth, ninety-four different types of atoms naturally exist, but eight of these elements make up 98.8 percent of the mass of the Earth: iron, oxygen, silicon, magnesium, sulfur, nickel, calcium, and aluminum. The rest are technically trace elements, including carbon. We have the technology to transform some of the common ones into the rare ones, but this requires a nuclear reactor, which costs even more money than mining and results in radioactive waste. This is essentially why gold is still valuable in the twenty-first century. If gathered together, all the gold ever mined would fit inside a large town house.

a material is not defined by its atomic ingredients alone. As we now know, the difference between hard transparent diamond and soft black graphite is not to do with their atoms: in both cases, they are made of exactly the same pure element, carbon. It is by changing how they are arranged, by altering them from a cubic structure into layers of hexagonal sheets, that the radical differences in their material properties are brought about. These structures are not arbitrary—you cannot create any structure—but are governed by the rules of quantum mechanics, which treat atoms not as singular particles but as an expression of many waves of probability.

This apparent alchemy illustrates that even with a very restricted set of atomic ingredients you can create materials with wildly different material properties. Our bodies are very good examples of this: we are mostly made of carbon, hydrogen, oxygen, and nitrogen, and yet through subtle rearrangements of the molecular structure of these ingredients, and the sprinkling of a few minerals such as calcium and potassium, an immense diversity of biomaterials results, from hair, to bone, to skin.