What is nanotechnology?
Nanotechnology is a way overused term, and I think the better term is nanoscience. Nanoscience is the study of things that are as small as molecules. Small things act very differently from large ones. For example, a gold nanowire is twenty times stronger than a large bar of gold. Electrons move differently through nanowires than through regular wires. We still have a lot to learn about the fundamental properties of nanoscale structures.
On the other hand, nanotechnology is about trying to make technologies, such as computers and medical devices, out of these nanoscale structures. Although the field of nanotechnology is fairly new, one might say that nanotechnology has been around for a while. The zinc oxide nanoparticles in that white stuff that people put on their noses for sunscreen could be considered a nanotechnology, for example.
In my lab, we do both nanoscience and nanotechnology. We work on designing and making the building blocks of nanotechnology: nanowires. We also are studying the fundamental properties of these building blocks. Finally, we are developing ways of organizing them into larger structures that could ultimately become part of useful technologies, such as computers.
How did you become interested in nanoscience?
After graduate school, I studied the behavior of materials that were so flat that they were essentially two-dimensional, such as the sheets you can peel off from mica and graphite. That led me to want to make materials that were one-dimensional—very skinny and long, like wires. So I started to work on the problem of developing a nanoscale wire. I also realized that these wires could be used to move information around in nanoscale devices, like computers.
What can be done with nanowires?
In the future, we will be able to make many common technologies using nanowires, but the processes we will use to make them will be very different from how those same technologies are manufactured today.
For example, transistors are crucial elements in computers. Today, manufacturers etch them out of silicon chips using multi-billion-dollar fabrication lines. The process is very expensive. In nanoscience, however, you can build from the bottom-up. You can literally take a bottle that contains a nanoscale silicon wire in a fluid, pour the contents onto some kind of surface, and make a nanoscale transistor. It’s cheap. My lab is also exploring ways of using interactions between chemicals or proteins to assemble nanoscale devices.
Of course, the next step is learning how to organize these small structures into larger devices, from computers to lasers to biological sensors.
What is a biological sensor?
Most biosensing today requires various chemical steps. When you get your blood drawn to get a test done, clinicians go through various procedures to see if you have some virus or protein present in your blood that is an indicator of disease. It can take hours or days.
On the other hand, our biological sensors use these little wires, which behave as transistors that turn on and off in response to specific biological molecules. The way transistors turn on and off in a computer is that you apply a voltage to them. But at the nanometer scale, that’s the same thing as binding a charged molecule to a wire. Proteins and viruses are charged, so we get a signal from the transistor when a protein or virus binds to the surface of the wire. The wires are treated to accept only the proteins or viruses we’re interested in, so we know immediately if the protein or virus is present in the blood.
How could a biological sensor be used?
Right now, someone who’s diabetic can buy a device that allows them to get their glucose level from just a pinprick of blood. Similarly, with the biological sensor, you could buy a device at CVS, spit on it or take a little pinprick of blood, and determine if you have the flu or any other viral disease.
I know from talking to doctors from the National Cancer Institute that they don’t have a way to do real-time monitoring of chemotherapy, so the doses they give patients are fairly crudely calculated. But if you could actually use a biological sensor to monitor the cancer marker proteins as the chemotherapy is being done, you could provide a much more sophisticated level of treatment for cancer patients.
We also have some really interesting but unpublished work for the defense department relating to biowarfare and chemical warfare agents. Most of the devices out there today for detecting these agents are one-element sensors—that is, they can only detect one type of molecule at a time. Like many blood tests, they’re not very fast. But in my lab we can routinely make sensors with ten elements that can simultaneously sense ten different toxins. You can get the readout in real time of whether there’s cholera, botulin toxin, or other things around. I think it’s a quantum leap ahead of any other technology, especially for real-time monitoring.
The sensor is a good technology because you don’t need it to be very complex for it to be useful—a 10-element sensor is 10 times better than any other test you can do today. A hundred elements are almost unimaginable to a doctor or clinician. The sensor is an application that can have a positive impact on society, while at the same time serving as a stepping stone to more complex integrated systems.
How long before biological sensors are widely available in medicine?
The science is almost done, and all of the pieces are essentially there. The major limitation at this point is not technical, it’s economic. A lot of venture capitalists don’t feel that diagnostics is a sufficiently profitable area to pursue. It’s also very difficult for any new technology to break into the market.
I’m very naïve in business. I hope that if something can really help people, we can find a way to make it available for them. It’s just going to take a lot of pushing on my part and others’.
How soon do you think that we will be able to pick something out in the nanotechnology section of Best Buy?
I would say 10 years. It’s going to be a while before we make nanotech electronic devices that are as sophisticated as electronics are today, and Best Buy won’t be interested in selling them until they are. But other markets might be more approachable.
For example, maybe you’ll go to the clothing store to buy nanotechnology. Something we’re working on is making devices in completely flexible plastics so you can have ubiquitous computing. You could wear a t-shirt that has your Palm Pilot built into it.
I believe that we’re still waiting for the “killer app” for nanotechnology. I think we need to think about the applications that best take advantage of the unique characteristics of nanoscience. What unique thing can we make from this technology that people really need? Once we figure that out, nanotechnology could be available in just about any store.
What’s the most exciting challenge in nanoscience that a young person might tackle in the next 10 or 20 years?
One of the biggest challenges is developing the underlying science and technology of how to assemble and integrate nanoscale structures, using our own bodies as an analogy. We start out from one simple cell, which divides and ultimately builds this really complex organism. Similarly, a single nanoscale device could be the starting point for making a computer if we could encode it with the right information. Once we know how to do that, we could build just about anything we can imagine. The person or people who solve that problem are going to completely open this up as a technology.
Another challenge for the future is to build at the interface between biology and manmade devices. If you take our biological sensors as the most primitive example, the sensor is actually converting a biochemical signal into a digital signal. It suggests that we have a way of building a very natural interface between biological and digital systems.
From what kinds of scientific backgrounds can you approach nanoscience?
Essentially any science. People who work with me come from biology, chemistry, physics, and engineering backgrounds. I haven’t stayed at all in chemistry—nanotechnology has given me an opportunity to continually learn new things. People who are very broadly knowledgeable are the ones who can put together the ideas that make the new steps forward. The field is completely interdisciplinary—you can’t stay focused in a traditional core area and make the breakthroughs that will drive the field in the future.
A lot is made of ethical issues in nanotechnology. Do you worry about making self-propagating devices that will run amok?
I think the concern about self-propagating machinery is not an issue right now in science, except possibly in reengineering viruses, which are already adapted to take over cells. We don’t reengineer viruses in my lab.
In nanoscience, one needs to take precautions more in the same way that you would take precautions with chemicals: You don’t want to ingest radioactive chemicals, carcinogens, or toxins.
Do you have any words of advice for our readers?
For young people interested in science or engineering, nanoscience is a fantastic area. There’s so much going on, it’s changing really fast, and it’s clear that we’re waiting for someone really innovative to come and lead the field in a better direction. I’m hoping I can do that in part, but I think there’s a real opportunity for a new generation of scientists.
Further Reading
Visual Aids
Charles Lieber’s lab developed a new method of building grids of crossed nanowires, which could be used in a nanocomputer. This collage depicts the array at different distances. The background image is a close-up of the nanowires. Credit: Charles M. Lieber, Harvard University.
In this animation, nanowires connected to electrodes act as transistors. When a virus binds to antibodies on the nanowire, it changes the electric current flowing through the wire. This device could be used to alert clinicians to the presence of a virus in saliva, blood, or the air. Credit: Charles M. Lieber, Harvard University.