Ask the Expert

Nanotechnology has become a buzzword, so a lot of “definitions” are flying around, but I like the gist of what the National Science Foundation says: Nanotechnology is the understanding and control of matter at the scale of 1 to 100 nanometers, where unique properties enable novel applications. In other words, it’s working on a scale so small —billionths of a meter—that there is a different set of rules and therefore completely new opportunities to invent useful things. Right now, for example, scores of Stanford engineers and scientists are working at this scale of individual atoms and molecules to create innovations that will benefit the environment, human health, and information technology.

What changes at the “nanoscale” is not the laws of physics, but which laws become most important. The everyday scale of people, animals, cars, and buildings is so big that we simply can’t notice what’s going on at the nanoscale. The most obvious influence on what we do is gravity. At the nanoscale, for example, other physical phenomena —namely “quantum mechanics”— have a dominant influence.

Two decades ago, Stanford Professor Emeritus Calvin Quate and collaborators at IBM co-developed the Atomic Force Microscope. It’s so sensitive that it can show us details on the scale of a billionth of a meter for a wide variety of materials and under normal (open air, room temperature) conditions. To do that, it “feels” its way across whatever sample it is examining using a probe with a tip only a few nanometers wide. Because the tip is so small, it can sense forces as it interacts with the sample that would be completely unnoticeable at a larger scale. That unique, nanoscale sensitivity has made it a uniquely valuable tool.

Much more recently in the Department of Materials Science and Engineering, Assistant Professor Yi Cui has devised a promising path toward increasing the capacity of lithium ion batteries by about 10 times. Recognizing that structures built at the nanoscale behave differently than larger structures, he was able to build incredibly thin silicon wires (“nanowires”) that, under the right conditions, can change their structure to get fatter and therefore hold more lithium ions. Inventing batteries with higher capacities could lead to increasing the driving range of emissions-free electric cars, or allow people using solar power to stay off the electric grid longer into the night.

Solar power is one of many technologies closely related to light. Fundamentally, light is emitted and absorbed by matter at the nanoscale. For us to create new technologies based on light, such as better solar panels, or energy efficient lasers for communications, we need to understand and control matter at that scale. Many research groups at Stanford and around the world, for example, are experimenting with nanoscale arrangements of different materials to search for solar panels that absorb more light, harvest energy more efficiently, and cost less than panels do today. We can do this because we can design and build structures at exactly the scale where light is produced and emitted.

On the medical front, working on the scale of billionths of a meter allows us to build electronic chips small enough to be inserted  into individual cells in the body. Physicians tell us that if we could sense the chemistry inside a disease-stricken cell, we’d know whether medicines were beginning to help. We might also get early information about problems emerging in healthy cells and we might someday even be able to help cells work better, much like a pacemaker helps the heart pump more regularly.

That example brings up the area in which nanotechnology has had the greatest impact: information technology. What allows you to listen to 4,000 songs on an iPod the size of a pack of chewing gum are computer chips with billions of components only about 50 nanometers across. Processors made up of similarly small devices allow your cell phone to recognize your voice and dial a number hands-free. Twenty years ago, that feat might have required 20 desktop computers linked together. It’s not just about doing the same thing, but smaller. The applications enabled by nanoscale electronics are fundamentally different when all you need is fractions of a computer chip instead of 20 computers. Think of mobile computing, for instance, or embedding sensors in materials to monitor for damage. Much of my research examines how nanotechnology might allow us to continue making information technology more powerful and to enable a fundamental change in the way we use information technology.

One way that nanotechnology is similar to other areas of exploratory research is that many ideas won’t work out the way we hope – that’s just the nature of research. A lot of early nanotechnology advocates were excited about the possibility of a future nanotechnology because they have discovered what can be done in principle. As an engineer, my goal is to determine which scientific discoveries can actually be turned into working technologies in practice and there is a lot of work to do to meet that challenge. Whenever we’re successful, we’ll see that working at this small scale can have a huge influence on the biggest technological needs we have. 

Related video

Wong's research group just produced this video about carbon nanotubes, which are long, thin tubes made up of a mesh of carbon atoms.