When materials scientists look at the periodic table of elements, they don’t see a chart full of symbols and numbers; they see a vast molecular pantry that allows a near-infinite number of recipes. Successful raids on this pantry can benefit all of us. Take solar power. In the 113 years between the discovery of the physics behind photovoltaic solar cells and the year 2000, less than 2 gigawatts of solar power capacity was installed around the world. But recent improvements in the molecular structure of the silicon in photovoltaic panels helped bring online more than 10 gigawatts of new solar power in 2011 alone. Or consider the improvements in desalination plants, where in the past four decades the energy required to turn seawater into clean drinking water has fallen an estimated 90 percent, due largely to improvements in the filters used to remove salts. Cleaner energy and more efficient ways to use it: As the world’s population steadily demands more resources, the ingenuity of materials scientists will become increasingly vital.
To understand the innovations unfolding now—and the ones that may lie ahead—DISCOVER partnered with the Chemical Heritage Foundation in Philadelphia to bring together six experts in materials science. Thomas Connelly is chief innovation officer at DuPont; he has managed the company’s Kevlar and Teflon businesses. Solid-state materials scientist Ryan Dirkx is vice president of R & D at Arkema, where he has worked on Plexiglas acrylic. Global intermediates technology manager at ExxonMobil, Mark Doriski has led production of the molecular building blocks used to create the versatile, chainlike molecules known as polymers. Chemist Greg Nelson is chief technology officer of Eastman Chemical. Chris Pappas is president of Styron, a company that develops plastics, latex, and synthetic rubber. And A. N. Sreeram, vice president of R & D at Dow’s Advanced Materials Division, works on the application of new materials in the health-care and automotive industries. Ivan Amato, author of
moderated their conversation.
HOW IS MATERIALS SCIENCE CHANGING THE WORLD NOW?
A. N. Sreeram: The easy answer is to look at personal electronics. But materials science has made aggressive innovation in other, more fundamental areas that are critically important for us, like shelter. Forty-eight percent of the energy footprint of the U.S. is spent in keeping our living spaces heated during winters and cooled during summertime. We have to conserve that energy. If you insulate your houses well, you can save a lot. Products like polystyrene blue board insulation, along with other materials to seal your windowsills, can substantially reduce leakage of energy from your house.
Chris Pappas: People think of innovation as the creation of brand-new things. But if you take basic molecules and arrange them in the right way, you can do a lot with what already exists. You can apply that to something like an automobile tire: You can change the physical properties of the rubber so that the tire has better rolling capabilities, no loss of wear, and no loss of wet grip. There is a kind of rubber, called solution styrene butadiene rubber, that grips just as well in the rain but doesn’t wear out as quickly. Tires that our partner companies are now working on can improve gas mileage by up to 10 percent, just by changing the tires, because this rubber rolls with less resistance.
Mark Doriski: Along those same lines, we have a synthetic lubricant called SpectraSyn Elite that allows us to improve fuel efficiency both at low temperatures, when you first start up any kind of machinery—for example, an automobile—and also at high temperatures. If you took the whole U.S. automobile fleet, which is more than 200 million cars, and converted one-third of the fleet from conventional lubricant to a synthetic, you could gain 2 percent fuel efficiency. That would save just under a billion gallons of gasoline per year; it’s like taking 1.5 million cars off the road.
Greg Nelson: A clean room [a low-dust, low-microbe environment where computer chips and other electronics are manufactured] is full of devices to push air through filters that scrub it. These applications require that more than 99.97 percent of all particles bigger than 0.3 micron [1/100,000 inch] be removed. That can use a lot of energy. A new technology called microfibers, which is being commercialized right now, allows us to do a higher-performance filtration in many of those systems while saving energy.
Ryan Dirkx: We have a polymer based on vegetable oil that is self-healing. You can cut this material and put it back together, and it will come back to 100 percent of its original strength in about two or three minutes. [Potential applications for self-healing materials include conveyor belts, shock absorbers, adhesives, paint, and asphalt.]
WHAT ARE THE NEXT BIG CHALLENGES FOR THE CHEMICAL INDUSTRY?
Thomas Connelly: Cars need to get smaller. I believe there is a future for the electric vehicle, but we have to find a way to come up with new materials—for motors, for energy storage, and for inverters, the devices that convert direct current (DC) to alternating current (AC)—and we need to really take weight out. Without those enabling inventions and the materials that allow them, we’re not going to be able to hit the energy goals we’ve set. There is a big challenge there.
Papps:LED lighting is another major materials science issue: diffusing the very energy-efficient light from LEDs through materials that have the right optical properties to provide the kind of light that we need; housing the components in a material that has the right physical properties for impact; addressing wear, non-yellowing, et cetera. led lighting is an emerging technology where materials science is just beginning to play a big role in achieving something for society with lower energy use and energy costs.
Dirkx: Another challenge is waste. When we start designing materials, we should be designing for repurposing, reuse. We would design a material differently if we had in mind the next three or four things it was going to be in its next lives. Take photovoltaic modules. It would be great if in a third or fourth life they could become trash bags.
Nelson: Yes, the grand challenge is to extend the lifetime of a product by making it more durable, and to get more uses out of it by having an end-of-life path. When we take on that challenge, we’ll have plenty of room for the new consumers that are coming up in emerging markets to step into the middle class and become a part of it. If we don’t take on that challenge, it’s going to be a much more difficult world to live in, because there’s not room for everybody to use energy at the rate at which we use it today.
Next Page: What Breakthroughs Lie Just Around the Corner?
WHAT BREAKTHROUGHS LIE JUST AROUND THE CORNER?
Pappas: One will be carbon nanotubes [see “What Happened to Nanotech?” below], which have fascinating material and electrical properties. But they are produced in messy bundles, and separating them in a way that allows them to be used has yields that are very low, 2 or 3 or 4 percent. The rest is waste. That’s a very high cost. Separating them with high yields will change the game. There are technologies today close to commercialization that I think will go a long way toward solving the problem. Then you’ll see the cost for nanotubes come down enough that they can be incorporated into everyday uses—perhaps tires, to increase durability.
Nelson: The largest source of new energy over the next 30 years will be saved energy: energy we’re using now that we’re going to save by getting more efficient. Real innovation is going to happen there.
Connelly: I think there is a basic change coming in the way biology is going to impact the world of materials science [see “Rise of the Biological Machines,” below]. You take a look at the ability to engineer organisms to produce a broad array of materials at room temperature, atmospheric pressure, in aqueous media with no exotic metals—this is going to radically impact the way we make materials for the future. Add to that the exquisite specificity of biology to allow us to produce materials more cost-effectively than conventional thermochemical processing, and to produce materials that you simply can’t make using conventional catalysis. That is a really transformative change, and it’s occurring right now.
WHAT HAPPENED TO NANOTECH?
In the 1990s the invention of atom-scale carbon cylinders known as carbon nanotubes convinced many scientists that nanotechnology—the manufacture of materials on the molecular level—was poised to revolutionize computing, medicine, and other fields. Twenty years on, there are no microscopic robots healing our bodies from the inside, but some nanoelectronic devices are almost market-ready, and several speculative applications are looking more plausible:
Generator Glove Wake Forest University physicist David Carroll has developed a nanotube-based fabric, called Power Felt, that creates an electric voltage from a difference in temperature—between your phone and your hand, for instance. Heat energy on one side of the material sets electrons in motion; they eventually slow down and accumulate on the cooler side, generating a voltage. In Carroll’s prototypes, Power Felt swatches can partially charge cell phones and flashlights. He estimates the fabric could be commercialized in a year.
Oil-Spill Sponge Nanoengineer Joseph Wang at the University of California, San Diego, is working on several types of nanomachines. His most recent is a cylindrical “submarine,” about the size of a red blood cell and made of gold, nickel, platinum, and a polymer, that can collect oil droplets in water. Swarms of the subs, able to carry 10 times their own volume, could help clean up oil spills.
Smart Matter The ultimate application of nanotech may be programmable matter, a substance that could change shape, color, and other traits on command. A collection of particles containing nanoscale computers to orchestrate those transformations could theoretically assume any form. MIT roboticist Daniela Rus has created a macroscale prototype for such devices. Her 1-centimeter “smart pebbles,” cubes made up of a microprocessor and electromagnets, can detect the shape of an object made from other cubes and join together to replicate it. Rus is also developing programmable fiberglass sheets that can fold themselves into different forms, including a miniature airplane (right).
RISE OF THE BIOLOGICAL MACHINES
The ever plunging cost of gene sequencing has not only revolutionized biology. It has also given engineers the tools to manipulate the natural functions of organisms in ways that were unimaginable only a decade ago, opening up rich sources of new biology-based materials. Two innovations announced this year illustrate the potential of such materials for portable power generation and high-speed computing.
Virus Batteries Seung-Wuk Lee, a bioengineer at the University of California, Berkeley, has found that a virus called M13 is a natural generator, responding to movements (such as the tap of a foot or the beat of a heart) by building up an electric charge. When a thin film of engineered M13 is sandwiched between two electrodes and subjected to mechanical stress, it generates power equivalent to one quarter that of a AAA battery–enough to light up a small LCD screen (see right). With further genetic tinkering of the virus’s proteins, Lee believes that he can elicit a charge 20 times stronger. “This viral material could one day be implanted in our bodies, because the virus is harmless to humans,” Lee says. “Then your heartbeat could be turned into electricity.” He foresees implanted, virus-based personal generators that would be permanent sources of energy for hearing aids and cell phones. Such technology could become commercially viable in little more than a decade, Lee maintains.
Kidney Computers At the Swiss Federal Institute of Technology in Zurich, a team headed by bioengineer Martin Fussenegger has engineered human cells to perform the binary calculations that form the basis of computing. Fussenegger created his biological calculator by engineering an embryonic kidney cell to respond to two different chemicals: erythromycin (an antibiotic) and phloretin (a compound found in apple trees). The cells responded to these “inputs” by glowing either red or green—the equivalent of digital ones and zeros. Organic circuits could someday be used as computers themselves; more intriguing, they could be embedded in our bodies to perform a range of medical functions. For instance, Fussenegger imagines biological circuits becoming sophisticated enough to use disease-related proteins as inputs. Such circuits could release insulin or other therapeutic compounds as soon as they detect the relevant medical condition.