Big possibilities from tiny technologies
One of the biggest new areas of scientific research is based on understanding unique and useful properties available on the smallest of scales. Researchers at Pacific Northwest National Laboratory and around the world are exploring nanoscience and nanotechnologies, where dimensions are in the range of one billionth of a meter. Bill Rogers manages Pacific Northwest's Nanoscience and Technology Initiative and was recently appointed the associate laboratory director for the Environmental and Health Science Division, which he renamed the Fundamental Science Division. When we talked with him about this emerging area, we asked him to explain when and why smaller is better.
What is nanotechnology and why is it getting so much attention?
Nanoscience refers to the study of phenomena that occur on the nanoscale—dimensions on the order of a small molecule and much, much smaller than the width of a single strand of hair. When system dimensions approach the nanoscale, some very unique and potentially useful properties emerge. Nanotechnology refers to taking advantage of these fundamental changes of physical properties. These properties are what we're interested in—momentum, heat and mass transport and electronic, magnetic and chemical properties. We're finding that size does make a difference.
Can you give me an example of a real-life application for nanotechnology?
Nanotechnology might make it possible to develop a safe and efficient way to use the sun's energy to convert water into oxygen and hydrogen. This kind of solution could be the answer for on-demand and on-location generation of hydrogen to power fuel cells.
The only material that can do this now without adding another energy source is anatase, a crystalline form of titanium dioxide. The problem is that after the photons from the sun are captured, there isn't much time for this chemical process to take place before the energy is lost. Also, the process is inefficient because it doesn't capture much of the sun's available energy.
We're putting very small particles of copper oxide—called nanodots or quantum dots—on a thin layer of anatase. This combination of metal oxides allows us to build nanostructures that have unique properties, such as the right electronic structure to harvest more energy from sunlight. It also provides a longer time for the desired reaction to take place, thus solving the two fundamental problems we've been butting our heads against. A device based on this type of tech-nology might be useful to NASA as they look for stand alone energy sources for their missions to Mars.
How is nanotechnology different from microtechnology?
In microtechnology, we're working with features that are a thousand times larger. Their properties are not fundamentally changing as the feature size is reduced. You can do things with engineering on the microscale to make reactions more efficient, but you're still dealing with essentially the same properties. That's what makes nanotechnology different. It focuses on the unique properties that exist only at the nanoscale.
In about 10 years we're going to run into a limit of how much we can scale things down in microelectronics. One alternative being hotly pursued involves coming up with completely different ways to make electronics, similar to the way the brain puts together electrical signals, using properties that are available only at the nanoscale.
Is this a new field?
What's new is our ability to image and manipulate matter on the molecular scale or nanoscale. Nanotechnology techniques have been around for centuries, but people didn't really understand what was happening. Today, we're building this understanding and we have technology available to begin taking advantage of it.
An early example of nanotechnology comes from the Chinese Lung Dynasty. Through trial and error, artisans in the 18th century used nanotechnology to create different colors for decorating vases. Depending on their size, pure gold particles reflect light differently. Particles that were about 4 nanometers gave light pink colors while 30-nanometer particles appear as deep reds.
Ben Franklin also was experimenting with nanotechnology years ago. Once in England, he put a teaspoon of oil on a choppy lake and the surface of the water became as smooth as glass. The oil spread into a layer only a single molecule thick and changed the properties that govern how the wind interacted with the water.
Here at the lab, we've been involved in activities over the last five years that are now called nanoscience, but they've been individual outgrowths of other programs. In October, we officially formed a new lab-wide initiative in hopes of bringing those efforts together and expanding into new areas.
What has led to recent growth in this area?
There are several advances in the last 15 years or so that have led to where we are today. One is the invention of molecular tweezers that allow researchers to trap a single atom and study its properties.
Another is the growing knowledge of self-assembling systems. Many people think that we can learn lessons from nature that will allow us to assemble things at the molecular level. No one's heart was built layer by layer, the way we make computer chips. It formed as part of prenatal development through a process called directed self-assembly. If we can learn more about what allows this to happen at just the right time and in just the right place, we could use similar techniques to build computers and small machines.
The developments we've seen have captured the attention of a wide segment of the population, including the federal government, which is putting hundreds of millions of dollars per year into this area of research over the next several years.
What is the focus of the federal government's initiative?
As a whole, it's pretty broad. After all, we're talking about studying phenomenon at a very small scale, which can intersect a lot of different areas of science. A total of $497 million is going toward the National Nanotechnology Initiative this fiscal year. It's going to many agencies such as the National Science Foundation, the National Institutes of Health, the National Aeronautics and Space Administration, and others.
Of that total, $36 million of new funding is going to the Department of Energy's Office of Basic Energy Sciences. They're focusing on four main areas that happen to closely align with the areas we're interested in here at Pacific Northwest.
Where do you expect Pacific Northwest to be involved?
In general, we want to apply nanotechnology to all DOE mission areas, not just fundamental science. We did a self-assessment last February and decided that we would pursue areas where we already have expertise and where we want to increase our capabilities.
The first is the broad area of nanosynthesis—working to build materials with tailored nanoscale features. This is our largest area of expertise. For example, we're supporting efforts to grow highly porous films using a ballistic deposition process, and we're using mesoporous materials as templates to grow supported and freestanding nanorods of metals, semi-conductors and oxides. Another area of strength and interest is in characterizing materials on the nanoscale. We will be imaging and characterizing material features on the nanoscale to better understand their properties and how they might be useful. We'll also be involved in certain aspects of what we call nanobiology such as immobilizing clusters of enzymes in nanosized pores for applications in chemical threat detection and decontamination. Finally, we will rely heavily on our computational expertise, such as theory, modeling and simulation to support and advance our experimental efforts.
We hope to build our expertise in soft material interfaces, or the interface between organic and inorganic systems. As we look to where the semiconductor industry is heading, all of a computer chip's critical dimensions are at the nanoscale. Incredible progress has been made in manipulating inorganic materials using top-down processing to make these devices. At the same time, we're trying to mimic nature and understand the way it handles electrical signals. As we learn more about how nature assembles things and builds them from the bottom up, and we continue making inorganic materials smaller and smaller, these two technologies will eventually intersect. Some very exciting science and technology will result at this intersection—the soft materials interface.
We're also trying to leverage other research initiatives here at the lab. The need to characterize single cells and single molecules is extremely important to building a better understanding of environmental threats to human health. These same techniques are needed in nanotechnology too.
Have we made any recent advances in this area?
Our scientists are developing an instrument that combines optical techniques with the capabilities of a scanning probe microscope, which is another one of those key developments that helped bring nanotechnology to the forefront. It is a really sharp pin that travels across a surface and allows people to learn about the topology of the surface. The marriage of these two techniques, if successful, will allow researchers to learn about the topology of a surface and the chemical composition of nanofeatures on the surface at the same time.