On a Spot Smaller
Than a Dime, UB Chemists Print Sensors That May Detect Hundreds of Chemicals
BUFFALO, N.Y. -- By borrowing a page from the
revolution, University at Buffalo chemists have taken a major step toward
placing hundreds, and possibly even thousands, of reusable chemical sensors in
an area smaller than a dime.
Their work, published in the March 1 issue of
Analytical Chemistry, which is currently online, could transform sensor
technology by providing agricultural, clinical, environmental and
pharmaceutical laboratories with a small, fast and portable methodology for
simultaneously detecting numerous chemicals in a sample a hundred or a
thousand times smaller than a drop of water.
A provisional patent has been filed.
The research overcomes a key obstacle in
exploiting high-tech materials, called xerogels, into which the UB team has
pioneered investigations as the basis of new chemical sensors.
Xerogels are porous glasses, developed through
sol-gel processing techniques in which a special solution reacts to form a
porous polymer. The resulting xerogel is a rigid material, like a glass, only
it consists of an intricate network of nanoscopic pores. In past work, the UB
group has developed innovative ways to stabilize and trap proteins within the
xerogels. These proteins then can be put to work to signal the presence of
important chemicals in a sample.
"We now understand very well the chemistry
involved in making good xerogels that contain active proteins," said
Frank V. Bright, Ph.D., co-author and associate chair and professor in the
Department of Chemistry in UB's College of Arts and Sciences.
The problem with traditional xerogel-based
sensors, he explained, is that they are large and designed to detect only one
chemical species. The UB researchers wanted to shrink down all of the sensor
technology so they could place multiple sensors in a small area and obtain
information on the presence of many chemicals in a single, small sample.
"The process of having to analyze for
different molecules one at a time is amazingly time-consuming, and it turns
out to waste a whole lot of the sample," said Bright.
Initially, Bright and Eun Jeong Cho, lead
author and doctoral candidate in the UB Department of Chemistry, micromachined
wells that were on the order of 1/25,000th of an inch in diameter on top of a
light emitting diode (LED), a tiny, inexpensive chip made of semiconducting
materials that can turn electrical energy into light.
"Using our xerogels in these wells on a
LED was a great idea on paper, but the volume of a well turns out to be fairly
small, about a billionth of a quart," said Bright. "Trying to fill
the wells turned out to be a nightmare."
But then Cho suggested pin-printing, a
technology widely used in genomics in which an extremely thin pin point sucks
up by capillary action small volumes of solution and deposits or prints them
onto microscope slides.
Using a commercial pin-printer, just like those
hard at work in DNA microarray facilities, the UB team had suddenly conquered
"Pin-printing is like taking a tiny quill
pen, dipping it into a solution and instead of filling wells, we contact-print
the sol-gel solution onto the surface directly to form an array of
xerogel-based sensors; we no longer need wells at all," Bright said.
"Because the volume delivered by these
pin-printers is less than a trillionth of a quart, the sensors are very small,
so we can cram many different sensors in a small footprint and, in principle,
detect hundreds or even thousands of chemical species simultaneously."
Bright and his team are now working on
pin-printing chemical sensors onto the top of an LED to form a fully
self-contained sensor array platform.
The work was funded by the National Science
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