 If you've been watching Risk Bides over the past six weeks, you'll have a pretty good idea what advanced materials are, and what might make them potentially risky. But there's one question that hasn't been addressed so far. Are we smart enough to create advanced materials that are safe by design? In principle, if we know what makes something harmful, we can design it to be less harmful. You're already seeing this with synthetic chemicals, where scientists are designing substances that do what they're supposed to do, but are gentler on the environment and our bodies. And there's nothing to stop us doing the same thing with other materials. Because advanced materials depend on designing and engineering substances to behave in a certain way, it's a relatively small step to including safety parameters in the design process. As long as we know what makes something harmful and how to reduce it. This safety by design approach is already being used in areas like green nanotechnology, an innovative approach to developing high performance materials that pose minimal risk to people and the environment. One example of safety by design and green nanotechnology is the use of advanced titanium dioxide nanoparticles in sunscreens. Many sunscreens use organic chemicals to protect the skin against the sun's ultraviolet rays. But to work, these chemicals have to be absorbed into the skin. And over time, the UV radiation breaks them down and makes them ineffective. This is why sunscreens need to be reapplied every few hours. Even organic sunscreens, on the other hand, work differently. Particles of an insoluble substance like titanium dioxide are applied to the surface of the skin where they reflect the UV light. But they can also reflect visible light and look kind of messy. However, making the particles small, around 20 nanometers in diameter, hits a sweet spot where they reflect the harmful UV light but are transparent to visible light. In other words, you have a highly effective yet invisible sunscreen. Apart from one small problem. Nanosized titanium dioxide particles are photoactive. Mix them with water and ultraviolet light and they produce free radicals, highly reactive chemicals that you really don't want to be exposed to. This isn't great news for the skin, but it also isn't great news for the product as the free radicals also kill long-term performance. To overcome this problem, one company engineered their sunscreen nanoparticles to be safe by designed by adding small amounts of the metal manganese. The result was highly effective UV protection without the production of harmful free radicals. Something that was only possible because of a combination of materials designed know-how and health risk smarts. As we learn more about how to make materials safe as well as useful, safety by design is likely to become an increasingly important way of ensuring products are acceptably safe and commercially viable. Of course, sometimes a fair dollop of creativity is needed to ensure both safety and functionality. Knives that don't cut, for instance, are still tough to make. But by combining science, design and engineering in innovative ways, risk and usefulness are no longer either or options when it comes to the next generation of materials. To the contrary, an intelligent understanding of risk is becoming an asset rather than a liability in making and using materials that support sustainable and profitable products. And this, from a risk perspective, is what makes advanced materials so exciting.