Revolutionizes Nano Imaging
Much faster technology allows AFM to capture nano movies, create
material properties images
ATLANTA (February 9, 2006) - While a microphone is useful for many
things, you probably wouldn't guess that it could help make movies of
molecules or measure physical and chemical properties of a material at
the nanoscale with just one poke.
Georgia Tech researchers have created a highly sensitive atomic force
microscopy (AFM) technology capable of high-speed imaging 100 times
faster than current AFM. This technology could prove invaluable for many
types of nano-research, in particular for measuring microelectronic
devices and observing fast biological interactions on the molecular
scale, even translating into movies of molecular interactions in real
time. The research, funded by the National Science Foundation and the
National Institutes of Health, appears in the February issue of Review
of Scientific Instruments.
Not only is FIRAT(tm) (Force sensing Integrated Readout and Active Tip)
much faster than AFM (the current workhorse of nanotech), it can capture
other measurements never before possible with AFM, including material
property imaging and parallel molecular assays for drug screening and
discovery. FIRAT could also speed up semiconductor metrology and even
enable fabrication of smaller devices. It can be added with little
effort to existing AFM systems for certain applications.
"I think this technology will eventually replace the current AFM," said
Dr. Levent Degertekin, head of the project and an asscoiate professor in
the Woodruff School of Mechanical Engineering at Georgia Tech. "We've
multiplied each of the old capabilities by at least 10, and it has lots
of new applications."
FIRAT solves two of AFM's chief disadvantages as a tool for examining
nanostructures - AFM doesn't record movies and it can't reveal
information on the physical characteristics of a surface, said Dr.
Calvin Quate, one of the inventors of AFM and a professor at Stanford
"It is possible that this device provides us with the 'ubiquitous' tool
for examining nanostructures," Quate added.
And what's the key to this dramatic increase in speed and capabilities?
A completely new microphone-inspired probe.
Current AFM scans surfaces with a thin cantilever with a sharp tip at
the end. An optical beam is bounced off the cantilever tip to measure
the deflection of the cantilever as the sharp tip moves over the surface
and interacts with the material being analyzed.
FIRAT works a bit like a cross between a pogo stick and a microphone. In
one version of the probe, the membrane with a sharp tip moves toward the
sample and just before it touches, it is pulled by attractive forces.
Much like a microphone diaphragm picks up sound vibrations, the FIRAT
membrane starts taking sensory readings well before it touches the
And when the tip hits the surface, the elasticity and stiffness of the
surface determines how hard the material pushes back against the tip. So
rather than just capturing a topography scan of the sample, FIRAT can
pick up a wide variety of other material properties.
"From just one scan, we can get topography, adhesion, stiffness,
elasticity, viscosity - pretty much everything," Degertekin said.
For a regular AFM to detect the features of the object, the actuator
must be large enough to move the cantilever up and down. The inertia of
this large actuator limits the scanning speed of the current AFM. But
FIRAT solves this problem by combining the actuator and the probe in a
structure smaller than the size of a head of a pin. With this
improvement, FIRAT can move over sample topography in a fraction of the
time it takes AFM to scan the same area.
Georgia Tech researchers have been able to use FIRAT with a commercial
AFM system to produce clear scans of nanoscale features at speeds as
high as 60 Hertz (or 60 lines per second). The same system was used to
image the topography as well as elastic and adhesive properties of
carbon nanotubes simultaneously, which is another first.
FIRAT's new speed and added features may open up many new applications
For instance, FIRAT is capable of scanning integrated circuits for
mechanical and material defects. And in biomolecular measurement
applications, FIRAT can scan the surface quickly enough for a researcher
to observe molecular interactions in real time.
"The potential is huge. AFM started as a topography tool and has
exploded to many more uses since. I'm sure people will find all sorts of
uses for FIRAT that I haven't imagined," Degertekin said.
FIRAT will be available for certain applications immediately, while
others may take a few years, Degertekin said.
The Georgia Institute of Technology is one of the nation's premiere
research universities. Ranked ninth among U.S. News & World Report's top
public universities, Georgia Tech educates more than 17,000 students
every year through its Colleges of Architecture, Computing, Engineering,
Liberal Arts, Management and Sciences. Tech maintains a diverse campus
and is among the nation's top producers of women and African-American
engineers. The Institute offers research opportunities to both
undergraduate and graduate students and is home to more than 100
interdisciplinary units plus the Georgia Tech Research Institute. During
the 2004-2005 academic year, Georgia Tech reached $357 million in new
research award funding. The Institute also maintains an international
presence with campuses in France and Singapore and partnerships
throughout the world.