Conducting research at the nano-level

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?