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"Our chip has a polymer enabling it to concentrate
the pollutants and a tiny built-in heater that drives them onto the
sensor," Mitra said. "It works like a bicycle pump. First our chip
accumulates the pollutants as a pump fills with air. Then, the chip
directs the tiny heater to send a large enough sampling of pollutants
- if they exist - to the sensor's head. With a large sample, the
sensor can recognize that pollutants exist."
"A Microfabricated Microconcentrator For Sensors
and Gas Chromatography," US Patent 7147695B2, was awarded to Mitra in
December of 2006. Research about the invention was previously
published in Sensors and Materials ("Design and Fabrication of
Microheaters for Microfluidic Channels") in 2006 and The Journal of
Chromatography A ("A Microfabricated Microconcentrator for Sensors and
Gas Chromatography") in 2003.
"The value of our sensing system is that it can see
pollutants even when they are present at very low concentrations,"
said Mitra. "Down the road, we hope to see this technology pave the
way for developing a small, inexpensive device to fit on a key chain.
These devices would do the same job as larger instruments used in
chemical laboratories for monitoring organic and other pollutants in
air and water."
Although many advances have been made in science,
it is still not as simple as many people imagine for scientists to
monitor pollutants. The consequences from automobile exhaust, the
dilution of cleaning solvents in air or the problems that occur when
tankers spill gasoline, remain of concern to scientists.
"Typical concentrations of many pollutants can be
small - only a few molecules of pollutants in every part per billion
of air or water molecules," Mitra said. "But even at these levels,
these pollutants pose a threat to human and public health."
"For example, we know that benzene, a by-product of
automobile exhaust, causes cancer," Mitra said. "The organics from
auto exhaust fumes also lead to smog formation in urban areas like Los
Angeles. Measuring benzene and similar chemicals, though, is costly
and difficult. One must have access to large instruments that cost
thousands of dollars. But using the microconcentrator, this will no
longer be the case."
Although the market currently features affordable
miniature sensors, the technology is not there yet for the tiniest
amounts of pollutants, said Mitra. "I'm talking about creating an
instrument sensitive enough to measure concentrations of pollutants
such as benzene, which may range in just a few parts per million or
even billion."
Mitra's research interests are two-pronged. He
looks for novel analytical techniques and sensors to discover
low-level trace elements in air, water and soil. His current projects
include developing instrumentation and methods for continuous, on-line
analysis of trace levels of organic pollutants in air and water. These
methods range from using gas chromatography or mass spectrometry to
micro-scale, lab-on-a-chip devices.
Mitra also looks for new ways to assemble and
modify carbon nanotubes to create novel and new materials to be used
in applications ranging from tennis rackets to rocket ships. Other
uses might include developing smaller nano chips for electronics (also
known as nano-electronics) and inexpensive, high-performance
throw-away chemical sensors. The latter might range from sensors for
clinical diagnostic purposes to using sensors to find toxic chemicals
in air, food or water.
Mitra has published 70 journal papers and is the
coauthor of Environmental Chemical Analysis (CRC Press, New York,
1998). He also edited Sample Preparation Techniques in Analytical
Chemistry (John Wiley, New York, 2003). Mitra holds five patents and
has made more than 150 presentations conferences.
Mitra received his PhD from Southern Illinois
University in 1988. |
