Conducting research at the nano-level

Ritesh Agarwal, an associate professor of materials science and engineering at Penn, researches nanotechnology.
Ritesh Agarwal, an associate professor of materials science and engineering at Penn, researches nanotechnology. (JOHN CARLANO)
Posted: August 08, 2011

For Ritesh Agarwal, it's the little things that count.

Agarwal researches nanotechnology. He says the most exciting aspect of his work is discovering how ordinary materials take on new and unexpected characteristics when reduced to nanosizes. Speed is one example.

In a study published online in Nature Materials last month, Agarwal's team members described how they engineered tiny nanoscale wires to smash a speed record - by a factor of 1,000 - for optical switches. The speed at which these switches turn on and off limits the processing power of conventional computers. A change, still far from commercialization, from gigahertz to terahertz could be revolutionary.

Staff writer Helen Shen spoke with Agarwal, an associate professor of materials science and engineering at the University of Pennsylvania, about the emergent nanoscale properties that are a hot area of research in the Philadelphia region.

Question: What does nanotechnology really mean?

Agarwal: Nanotechnology refers to technology and science that happen when you manipulate materials at the nanometer-length scale - about 10,000 times smaller than the thickness of a human hair.

Q: Is nanotechnology just about size?

Agarwal: If you make things small, you can of course pack things closer and increase the density of electronic devices. But research has also shown that the fundamental mechanical, chemical, optical, and electronic properties change drastically at the nanoscale. And there lies the real advantage.

Take gold, for example. With chunks smaller than 100 nanometers, properties start to change. The color of this gold particle actually changes. A solution of gold particles, as you start to make the particles smaller, first will turn blue around 50 nanometers, and then red around 20 nanometers in size.

It's an uncharted territory; there's little theoretical basis for predicting how these materials will behave at the nanoscale, but that's also what's totally exciting and new about our research.

Q: Are modern nanotechnologies confined to the lab?

Agarwal: There already are some products that make use of them. One example is the home pregnancy test, which uses sensors containing gold particles. If you add a certain chemical associated with pregnancy, this leads to the coalescence of the gold particles, and this change leads to a different color.

Q: Are nanoparticles safe?

Agarwal: There's a lot of debate and argument and research in this area. If you take the example of genetically modified food, it shows how you really have to take public confidence and trust into consideration along with research progress.

Once we have nanotechnology products widely available in the market, how you dispose of them, how nanoparticles can get into the environment, how they can affect the body - these are all issues the research community is taking very seriously.

There's no definitive answer yet, but the important thing is to educate the public as we go along. Research into safety is systematically happening alongside other nanotechnology research.

Q: What are the applications to computing?

Agarwal: Current technology for making computer chips uses light to etch out the pattern of a circuit onto a silicon wafer. The size of these devices is limited by the wavelength of light you use, and in order to continue making smaller devices, companies are using shorter and shorter wavelengths of light. But this gets incredibly expensive.

There are new techniques now that use chemistry to coax atoms and molecules to self-assemble into tiny structures - nanoscale particles, wires and tubes, and these can be the building blocks for new devices. Under the right conditions, you can design and control precisely the size and shape of these particles.

In principle these techniques could be cheaper. Our goal in the future will be to make large-scale devices with nanoparticles at lower costs.

Q: What is the next big area?

Agarwal: Nanotechnology applications in biology - in medical diagnostics and drug delivery, especially.

One important drug-delivery problem is targeted delivery, getting drugs and treatments to exactly the problem area. Researchers have been able to functionalize the surface of nanoparticles, meaning that you can attach medicine and other useful molecules to them. And, as opposed to giving a drug that diffuses all over the body through the bloodstream, the nanoparticles can be engineered to find the right location and can get to places other drugs can't.

Gold nanoparticles, if you shine infrared light on them, heat up. If these particles have attached themselves to a tumor, for example, if you then shine infrared light on them, they will heat up and bombard the tumor.

It's not just medicine, though. I think almost every area of science and technology will be using products on the nanoscale: electronics, communications, biology, therapeutics. I don't think there will be any field that won't be affected over the next 20 to 50 years.


Contact staff writer Helen Shen at 215-854-4802 or HShen@philly.com.

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