You don’t hear much talk about it anymore, but one of the tacit promises held out by the field of nanotechnology has been ”material by design.” To solve a specific problem using this ”bottom-up” approach—say, creating a material engineered for efficient hydrogen storage—you design and create structures, atom by atom or molecule by molecule, that provide the functionality needed for a particular application.
But despite government task forces and lots of fascinating nanoscale research (like the beautiful model of the first 3-D assembly of magnetic and semiconducting nanoparticles shown here), material by design isn’t even on the horizon, certainly not for the production of bulk commercial materials. The goal of an ambitious business alliance launched in 1996, the Chemical Industry Vision2020 Technology Partnership, was to have designer materials in production by 2020. In fact, we are so far from that goal it’s not clear whether we will ever be able to overcome all the obstacles.
Unfortunately, nanotechnology in the marketplace is still a ”top-down” discipline that can only begin to approximate material by design. Novel nanomaterials and structures are discovered, their properties are determined, applications are sought out that may need those particular properties, and then it is finally determined whether there is any commercial need for applying the nanomaterial to an application. Chemical and material companies will produce what the market demands, in a way that promises the greatest profits. When talking about bulk chemicals and materials, it is nearly impossible to think about producing these atom by atom, because you can get to the same material by just following a hit-or-miss iterative process, and do so far more cheaply.
Some of the obstacles facing material by design would have been hard to appreciate in the nanoloving 1990s, when the Vision2020 group, all highly respected scientists from research institutes and the chemical industry, came together to develop a road map for their dream of creating custom nanomaterials.
One major roadblock is scientific. If we are ever to reach a point where we can take a certain requirement, and then be able to go to a computer and design the material that is ideal for this purpose, we are going to have to overcome some fundamental problems of material science. Currently, we don’t even have a good grasp of how combining materials into particular compounds gives them certain properties, or how these properties give materials functional qualities.
A second major problem is computational. Not only do we not understand the basic physical principles we need to model, there are at the moment no computers powerful enough to predict how certain material structures yield particular properties. When it comes to solid matter, systems are so complex that current computer modeling tools quickly run out of steam. Granted, algorithms and processing power are always improving, but it would take orders-of- magnitude improvements for computers to reach the predictive power required to address these issues.
Any useful software modeling would need to be able to reveal how a material’s structural alterations—for example, a change in a crystal’s lattice structure—affect its properties and functions. Such a program would also need to be able to do that in a range of scales, because we also don’t know whether we must look at the atomic or particle level to find out where effects are taking place.
The bottom line: material by design may elude us for centuries. Hit-or-miss approaches to large-scale commercial nanotechnology look more promising for now, but even here our ability to manipulate materials at the nanoscale for commercial applications may come down to serendipity rather than scientific method and design.
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About the Author
Guest editorial by Dexter Johnson, program director at Cientifica, a nanotechnology consulting firm, and blogger for IEEE Spectrum Online (http://www.spectrum.ieee.org).