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Small
wonders
Nanotech grants for probing inner space
By Tim Stoddard
For young Benjamin Braddock in the 1967 film The Graduate, the future was neatly summarized in one word: plastics. If Mike Nichols had directed the film 30 years later, that word may well have been nano.
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| Selim Unlu (left), an ENG associate professor of electrical and computer engineering, and Bennett Goldberg, a CAS professor of physics, are not lone wolves in the laboratory. The two share a lab in the Photonics Center, and they say that the collaborative arrangement is conducive to problem solving in their field of nanoscience. Now they’re heading up the Nanoscience Working Group to encourage similar interdisciplinary relationships among CAS and ENG researchers working in nanotechnology. Photo by Kalman Zabarsky |
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Nanoscale science and technology are expected to change virtually every
human-made object in the next century. The essence of nanoscience involves
manipulating atoms and molecules to build structures with new and improved
properties. In the 1980s, when researchers first started working at the
nanoscale (a nanometer is one billionth of a meter, or about 1,000 times
smaller than the diameter of a single human hair), they were surprised
to find that small groups of atoms or molecules often have unexpected
properties, such as increased strength, electrical resistance, and optical
absorption, that are significantly different from the properties of the
same matter when it is a single molecule or part of a vast array of connected
molecules.
Over the past three years, BU researchers have been pursuing several ambitious
nanoscience projects. But until now, says Bennett Goldberg, a CAS professor
of physics, these disparate efforts have been limited by their lack of
collaboration. In the first step towards building an intercollege working
group of engineers, physicists, biologists, and chemists, Goldberg and
Selim Unlu, an ENG associate professor of electrical and computer engineering,
have received funding from the National Science Foundation (NSF) and the
National Institutes of Health (NIH) to begin two interdisciplinary projects
in the field of nano-optics, which strives to see tiny objects in ever-finer
detail.
Nano-optics is an important starting point, because to fully make use
of the potential of nanotechnology, researchers need to see what they’re
working with. With a $1.3 million grant from the NSF, Unlu and Goldberg
will develop tools and methods for seeing objects 10 to 20 nanometers
wide. The project is one of several NSF grants to support nanoscale interdisciplinary
research teams (NIRTs) at universities across the country. BU’s
NIRT team includes Todd Murray and Kamil Ekinci, both ENG assistant professors
of aerospace and mechanical engineering, and Raj Mohanty, a CAS assistant
professor of physics.
The team’s initial goal is to get around a fundamental limit of
nature. For 300 years, optical microscopes have been limited by the way
light behaves. It’s impossible for even the most powerful lenses
to see things smaller than about one half the wavelength of light, the
so-called diffraction limit. A decade ago, Unlu and Goldberg pioneered
a technique called near-field optics to get around this limit. Now they’re
developing an even better technique called solid immersion microscopy.
The idea is to shorten the wavelength of the light by passing it through
a substance with a very high index of refraction. The higher the index,
the slower the speed of light in that medium and the shorter the wavelength.
In a separate project, Goldberg and Unlu have received $1.7
million from the NIH to apply a different sort of nano-optics to observe
the subcellular structures of Shigella bacteria. With Anna Swan, an ENG
research assistant professor of electrical and computer engineering, Unlu
and Goldberg will refine a new technique called self-interference fluorescence
microscopy. One of the main tools for probing biological systems, fluorescence
microscopy involves injecting a fluorescent molecule into the specimen
and tracking its position with a microscope. Currently researchers can
use this technique to see things as small as 400 nanometers, but Unlu
and Goldberg’s team wants to better that by a factor of 50 using
their patented technique.
Other instruments, such as electron microscopes, can already render images
of biological features at a much higher resolution. But the problem with
this technique, explains Goldberg, is that it requires killing the cell,
freezing it, and slicing it thinly before bombarding it with high-energy
electrons, which damage the sample as they bounce off it. The goal is
to develop an instrument that can locate, in real-time and three-dimensional
space, the precise position of certain proteins in living bacteria and
viruses.
For Goldberg, the NIH-funded project illustrates the importance of interdisciplinary
work in nanoscience. “The real breakthroughs and advances in nanoscience
are going to happen at the boundaries between disciplines,” he says.
“It’s pretty unusual for me, a condensed-matter physicist,
to have an NIH grant to do biological imaging. As we understand more about
the physical processes of things at the nanoscale, then the great application
is to match them to the natural biological systems at the same scale.”
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8 November 2002
Boston University
Office of University Relations