Advanced Materials

Transcription

What are advanced materials? And are they safe? To start with, we need to go back to the very beginning. Humans are great taking lumps of stuff and making them useful. Our ancestors, for instance, were pretty good at using materials like stone and clay and bronze and to make tools and other useful objects. This ability to design and engineer products from the basic materials around us is what has enabled human civilization to become what it is today as a species we have been incredibly successful in changing our lives by adding value to the materials we mine, or grow or otherwise collect. But until recently how we made use of these materials was limited by what we could see with our eyes and what we could touch with our hands. Then we discovered atoms, and everything changed. Over the period of a few decades at the beginning of the 20th century scientists and engineers went from being limited by what they could see and touch to being able to play with the basic building blocks of all materials. It was a pivotal point in human development and one that we are only just beginning to realize the full significance of. But what does this mean for advanced materials? Next we'll look at how the atomic revolution opened the door to a new age of materials engineering, and how this paved the way to the modern era of advanced designer materials. At this point we've looked at how our ability to design and engineer the materials around us has got us to where we are today. But we also saw that, for millennia, people were limited in how they made use of these materials by what they could see with our eyes, and what they could touch with their hands. All of this changed when we discovered atoms and how to play with them. At the beginning of the 20th century scientist confirmed that everything around us is made of atoms - something we take for granted now, but it wasn't so obvious a hundred years ago. Researchers quickly developed instruments that allowed them to see how these atoms come together to create materials. These instruments enabled them to start working out how what a material does depends not only on which atoms it's made of, but how they are arranged together. Then they discovered how to create new materials by putting atoms together in different ways, and the world changed. Of course this didn't all happen overnight. The first breakthroughs came about in the early nineteen hundred's, when techniques such as X-ray diffraction and electron microscopy allowed scientists to "see" for the first time how atoms form materials. And to understand that how materials behave at the macroscopic scale depends on how the atoms are arranged at a microscopic level. And it wasn't just stuff like metals and other inorganic materials that they were exploring. Scientists used the same techniques to learn how organic materials were constructed and how they functioned. All the way down to the DNA and the proteins that are at the core of all living things. Once scientists and engineers had discovered the atomic rules of material construction, they set about designing new materials. Using newly developed synthesis and construction techniques, they started to make designer chemicals. And they quickly moved on to more complex materials: Materials that were stronger and lighter; that conducted electricity and heat better; that transmitted or blocked light and other forms of radiation more effectively; and did other things that had previously be out of reach. And they achieved this by manipulating the structure of these materials at an incredibly fine scale. But researchers were still limited by the finesse with which they could engineer materials at the finest level. They knew that if only they could play around with the atoms themselves, they could do incredible things. Fifty years ago they didn't have the tools and the skill to do this. Now they do. And this is what's opened the door to a new era of advanced materials. Materials that are intentionally designed and engineered from the atomic level up. And designed to do things that were this stuff up science fiction until just a few years ago. Next, we'll begin to look at how these advanced materials are beginning to change our world. At this point, we've looked at how our ability to design and engineer materials from atoms up has launched a new era of advanced materials. Next, we take a whistle-stop tour of how these designer materials are beginning to transform the things we make, and how we use them. Over the past 100 years we have discovered how the arrangement of atoms in materials influences how those materials behave. And we've started to use this understanding to design and create new materials that have never before existed. This heady combination of new knowledge and new tools and techniques for manipulating matter is enabling scientists and engineers to create products that were unimaginable just a few years ago. We've affectively opened nature's toolbox and we're starting to play rather seriously with what we found. Admittedly we're still learning how to use these tools, and our knowledge is rather patchy in some areas. But already researchers are using them to create an incredible array of materials that push the bounds at the possible. Materials, for instance, that are lighter stronger and tougher than ever before. Materials that generate and bend and absorb light in unusual ways. Materials that convert sunlight and heat and movement to electricity and other forms of energy. Materials that help get drugs to where they need to be in the body, and prevent disease and help create high performance replacement body parts. And keep food fresh. And make food healthier. Materials that help chemical reactions go faster, and that mimic and improve on biology. And that allow cells and viruses and organisms to work differently. Materials that enable faster, more powerful computers. And computers that are just plain different. Like quantum computers for instance. And we've only just started. As our understanding increases, will see more and more sophisticated materials being developed. Like materials that adapt to their surroundings, and change their behavior accordingly. And hybrid materials that combined different advanced materials into super-advanced materials. Even materials that blur the boundaries between living systems, and everything else. Now that we have the keys to the building blocks of everything, we are really only limited by the laws of physics and our imaginations. Without a doubt, we leave in exciting times. But are these designer materials safe, or are we playing a dangerous game here, with little thought at the consequences? it's a smart question. Advanced materials are designed to behave differently from more conventional materials. And it's reasonable to assume that that this different behavior could lead to different risk. The safety question has led to millions of dollars worth of research into the safety of one particular group with advanced materials over the past decade: engineered nanomaterials. And for good reason. Our bodies have evolved over millennia to handle the natural materials we have evolved alongside. And even then they're not perfect. So how are they expected to cope with something that has never before existed in the history of humanity? Like for instance precisely engineered nanoparticles of gold or silver? Or other substances? And what happens when something that has been designed to, say, speed up chemical reactions; or be part of a super strong material; or to convert one form of energy into another, gets into our body? Do these unique and unusual properties also lead to unique an unusual risks? If advanced materials are going to be as useful as we think they could be, these are really important questions. The last thing we need is a wonder material that ends up causing disease, or harming the environment. Its not good for the people it affects, and it's certainly not good for business. But how do we know what makes an advance material potentially dangerous and how future risks can be avoided? To answer that, we need to start with what we know about what makes any material risky, and build up from there. Exploring the potential ways new materials can cause harm is important. If you want to make money from advanced materials and the products they're used in, maiming or killing your clientele in the process is not a great business strategy. And surprising as it may seem, many folks in business would rather be improving people's lives than making them worse. But if you've got a brand new never before used material, how do you know what it might do that you probably don't want it to? One approach is to assume the worst. Maybe that novel never-before-seen nanoparticle for instance could burrow into your brain, replicate itself, and bring about the next zombie apocalypse. Maybe it could. But probably it won't. Fortunately, a firm grasp of scientific reality, past experience and some risk analysis know-how, go a long way to helping predict the likely ways a new material might be harmful, and how that harm can be avoided. The first thing to ask if you're interested in health risk is, "can this new wonder material get into your body?" The obvious ways a material can get into your body is through your mouth, or going up your nose, or diffusing through your skin. If there's a way in, we need to consider the harm that could be caused by the material as a result. But it's there isn't a way in, there's little chance of harm occurring. For example, a single carbon nanotube could be inhaled or ingested and get into your body that way. But wrap it up in an iPhone, and unless you have some rather odd eating habits, it'll probably stay in the phone and not get into you. But what if in advanced material does get into your body? Over millennia, we've lived in some pretty cruddy environments as humans. And as a result our bodies have evolved to handle stuff that could be harmful. It's a neat survival trick that has helped us to stick around for as long as we have. For many advanced materials, our bodies will process and eliminate them just as effectively as other materials. Just because we think they're fancy, doesn't mean our bodies do. But there are some warning signs we've learned to look out for in materials that our bodies don't handle so well. Particles that get into us and don't dissolve or degrade easily aren't great news for instance. Neither are particles that are long and thin like fibers. Or crystalline. Or small enough to slip into places they shouldn't. Or materials that release known toxic chemicals. These are all characteristics that scream "Watch Out!" if they're present in a brand-new, never before tested advanced material. In other words, out of the vast array of advanced materials we could be using, some may need to be handled with special care. But only a small number of these materials will have the potential to get into our bodies and cause harm. Of these, only some will overcome or slip by the body's defenses and cause serious harm. And of these, fewer still will cause harm in ways we weren't expecting. And a very small number of materials indeed will lead to new diseases. As a colleague of mine likes to point out, the body only has a limited number of ways of saying "ouch!" By using scientific understanding and expert knowledge, many of the potential risks associated with advanced materials can be spotted and managed, or avoided altogether. That said, the are bound to be unknown unknowns. Those things that a new-fangled material does that no one thought of beforehand. While second-guessing what these might look like can be a dangerous game, it's important to continue researching possible risks, just so we not caught with our pants down when something unpleasant does eventually turn up. This of course raises an important question: Do novel materials present novel risks? Novelty is a big part of advanced materials. Not novelty in terms of amusement of course, although the inventors of silly putty may beg to differ. But novelty as in something that's new or unusual. If you can design and engineer a material that behaves differently to other materials, you open the door to improving existing products and inventing exciting new ones. If you get it right, you could make a financial killing. But novel materials can also help find solutions to some really stubborn challenges, like ensuring everyone has enough food and water, and energy for instance. This is fantastic. As long as your fancy new material doesn't create more problems than it solves. And here's the rub. How do we know that that these novel materials don't come pre-packaged with novel risks? On the surface, the question makes a lot of sense. If a material is designed to behave in unusual ways, who's to say that that unusual behavior want lead to usual biological impacts, that in turn lead to unusual harm and unusual diseases? However, this is also a somewhat misleading question. And here's why: From a human health perspective, we're interested in risk; what could cause harm; how does it do it; how much harm could potentially be caused; and how can we reduce or avoid this. As far as our bodies are concerned, they couldn't care less about where a risk is novel or not. They're just interested in whether something is going to hurt, and how to avoid that hurt. For instance, if you hit your thumb with the latest nanocomposite metamaterial super-hydro whatever hammer, the instrument of destruction may be highly novel, but the pain will be the same as if you'd used your grandmother's antique nail wacker. The novelty is in the hammer, but not in the harm it causes. The danger here is that focusing on novelty rather than risk, diminishes the importance of the actual harm that a material could cause. It implies that the only interesting risks are the new and unusual ones. And it ignores the reality that many common risks associated with materials, novel or otherwise, remain highly important and poorly understood. When it comes to novel materials and advanced materials more generally, a much better question is "can this material potentially cause harm?", followed quickly by "under what circumstances?"; "what type of harm?"; "how much?"; and "how can it be avoided?". These questions focus on impact rather than novelty, and recognize that many novel materials may in fact present rather mundane risks, that nevertheless still needs to be dealt with. Of course there's still the chance that a novel material will do something entirely unexpected if it gets into your body. This is where we need scientists asking the difficult questions, just in case something new does come up. But until it does, fixating on novel risks runs the risk of overlooking the more boring risks that are likely to be a problem, unless dealt with. At this point, 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. We're already seeing this with synthetic chemicals, where scientists are designing substances that do what they're supposed to do, but re 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 to 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 needs to be reapplied every few hours. Inorganic 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 reflects visible light, and look kinda 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. Nano-sized titanium dioxide particles are photo-active. 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 design, by adding small amounts at 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 design know-how, and health risks smarts. As we learn more about how to make material 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 dollar of creativity is needed to ensure both safety and functionality. Sharp 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 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.