A pioneer in green nanotechnology, University of Oregon professor James Hutchison proposes creating safety-approved nanoscale building blocks nanoparticle lines and arrays that would integrate smoothly with existing silicon chip-processing steps. Hutchison is the director of the Materials Science Institute on the university's Eugene campus. Brooks-Cole last year published his book Green Organic Chemistry: Strategies, Tools and Laboratory Experiments. The director of the Green Chemistry Institute, Paul Anastas, has singled out Hutchison's work on what Anastas calls a "conceptual template for designing nanomaterials using green chemistry."
EE Times: What's your philosophy regarding green chemistry and how it applies to nanotechnology?
James Hutchison: Others have defined green chemistry, pretty extensively over the last 10 to 15 years, to show how it can help us develop products that do less harm to the environment or human health. Also, how do you develop a process to make materials in a way that is very efficient and prevents pollution? Those strategies map extremely well onto nanoscience. Currently there is concern about some of the potential biological impacts of nanomaterials, and green chemistry is a powerful tool to design those materials so they won't be harmful.
That is [only] half of the equation the product part, where green chemistry is a way to make sure nanotechnology develops in a responsible fashion. On the other hand, many nanomaterials that are going to be made are likely to be rather complex materials, and over time we have seen that complex materials, for example pharmaceuticals, generate more waste than simpler molecules, like those made in the petroleum industry.
In terms of how nanotechnology can benefit from green chemistry on the process side, we look at alternative reaction methods and at taking advantage of things like self-assembly, which will allow us to make materials, complex devices and structures in a much more efficient fashion.
EET: So you are using less-toxic chemicals and being more responsible with the toxins you do use.
J.H.: Yes, those are very important tenets of green chemistry reduce the toxicity of what you use, use less and also think about what happens to the products when you are done with them [that is, ask] if they can be easily recycled. That is a different design paradigm than just designing for the highest performance.
EET: Or the lowest cost.
J.H.: Or the lowest cost. But though the green chemistry community certainly believes that it is great to do things that are good for the environment, [the solution] also has to be cost-effective; otherwise, people won't use it.
There is the belief that being green always means that your solution won't be competitive, that it won't be the highest-performance. But there are many examples now that show you can design something that is much better for the environment and human health but that is also the least-expensive and the highest-performance approach.
EET: If you've got all those in the formula, then you don't need regulation; people will just naturally use it.
J.H.: That was actually the main driving force behind green chemistry in the U.S. to give industry an opportunity to be proactive and prevent regulations from being necessary.
EET: You launched the first green chemistry lab that specializes in nanotechnology. How is your lab different, and what are your plans for it?
J.H.: It's the right time to apply green chemistry to nanoscience because nanoscience is in such an early phase. It's better to bring green chemistry into a field before an incredible capital investment has already been made. Since the whole concept of nanotechnology is to use molecular-level design to make better products and more efficient processes, the best time to do that is at the very beginning of a new phase of technology.
So that is why there is such a unique opportunity with nanoscience and nanotechnology. And what we are doing in my group is looking at those various aspects. How do you design nanoparticles that have all the optical and electronic properties that you want the high-technology part that you want but at the same time design them so that they will not be harmful to the environment? That is a big challenge.
The other thing is that, on the lab scale, people make nanoparticles all the time, but they often use harsh reagents or less-efficient methods. When you think about having to scale [laboratory methods] up [for manufacturing], it could be quite daunting. So we have good, efficient, hazard-free chemistry to make those new materials that we hope will become the building blocks of nanotechnology.
EET: That brings us to your first patent a greener, faster way to synthesize gold nanoparticles. Tell us about that.
J.H.: For a number of years, we have used a nanoparticle building block a very small particle that has only about 100 atoms of gold at its core and has a molecular ligand shell around it that keeps the gold cores from aggregating. In the past we had to use diborane gas, which is a highly toxic gas that auto-ignites in the air at low temperatures, so it is quite hazardous to work with. And the solvent used was benzene, which everybody is trying to get away from because of its potential carcinogenicity. So we replaced the diborane gas with sodium borohydride (a solid) and the benzene solvent with toluene. Those changes made the process a lot cleaner, but the other thing you get is that it's much more efficient: It's easier to make larger quantities, it's obviously safe, and it's much less expensive than the old method.
EET: Which is why, I guess, you applied for a patent on it?
J.H.: Yes, it's a win, win, win situation great for the environment, but also much more competitive, easier and safer.
EET: Your second patent was granted just last month, and apparently it could lead to a new kind of nanoscale optics and electronics using ultrasmall transistors that operate efficiently at room temperature. Tell us about it.
J.H.: The first patent was about nanoscale building blocks. The reason we wanted those building blocks is that there is a chance to change the paradigm that people currently apply to make ultrasmall optical and electronic devices.
The current strategy is a top-down or subtractive approach, where you take a block of semiconductor and chisel away at it with chemical-processing steps to make the devices. I like to use the analogy that if you are making a statue, you take a chunk of marble and you chip away at it in that fashion, removing all the exterior marble that you are chiseling away.
An alternative approach would actually be to build from the bottom up, and that is what we intend to do with the nanoscale building blocks. It's a lot more like taking a bunch of Lego blocks and building a statue out of that. And in that case, all of those blocks that you use actually end up in the product. It's much more material-efficient it's an additive process.
What we are doing with the nanoscale building blocks the nanoparticles is then coupling them to biopolymer "scaffolds" to be able to self-assemble lines and two-dimensional arrays of nanoparticles to use as a basis for ultrasmall electronic devices.
EET: Would those be integrated with traditional silicon devices, or are we talking about a whole new type of chip?
J.H.: When we look at these sorts of materials, given the fact that silicon processing is so heavily entrenched, the first opportunity is to make hybrid devices that combine the best aspects of silicon with the best properties of the nanoparticles.
Ultimately, if you want to get the smallest possible devices, you might want what we call molecular integration, where you use these polymeric templates to fully integrate these nanoparticle arrays to each other. That's a few years off; we don't expect to see that right away. But there is a great opportunity now to develop these hybrid structures that take advantage of the incredible strength of silicon-based electronics.
EET: So the silicon processing would probably be done first, because it will be done at higher temperatures?
J.H.: Yes, that would probably be done first, and then, near the end of the device fabrication, there would be the opportunity to integrate the nanoparticles.
We will have a paper coming out soon in Advanced Materials that will show how you can use the same photolithography steps already used for silicon processing to pattern gold nanoparticles on silicon.
EET: You are also the director of the University of Oregon's Materials Science Institute and a member of the Oregon Nanoscience and Microtechnologies Institute.
J.H.: That's right. It's a very exciting program that brings together the strengths of the three major Oregon Universities and the Pacific Northwest National Laboratory to address a lot of different scientific and technological problems that reside within the size or length scale between the nanoscale through the mesoscale to the microscale. There is a considerable focus of interest on the problems of the nano- and microscale industries, particularly in our region, in the Silicon Forest.
EET: What is your reaction to the dire predictions by Bill Joy, the co-founder of Sun Microsystems, that the proliferation of nanobots will blanket the planet in "gray goo"?
J.H.: Most of the people working in nanoscience are not particularly concerned about that version of an environmental catastrophe. I think that the nanomaterials that people are currently studying don't have that level of sophistication. At this stage, we are more interested in what the passive hazards of these materials are.
You always have to worry about whether a new technology will have unexpected consequences. It's important to make sure that there is not some hidden hazard. But I don't think we have to worry about nanobots self-replicating and consuming the world's resources.
I do think that there are exciting possibilities in this area of ultrasmall electronic devices. We have been able to show how small we can really make these devices or, really, how small the features are that we can make, with patterning on the scale of tens of angstroms.
This is a great opportunity to engage across the basic sciences and engineering, to figure out how to take full advantage of that. It's probably not going to be the same sort of computing strategies that we use at larger scales.
We can also go three-dimensional with these structures. Instead of planar technologies, we can start to think about three-dimensional technologies that are ultrasmall. How do we take advantage of that? That's a really interesting challenge that I hope will get interdisciplinary teams involved all the way from the synthetics chemist to the engineering communities.