1 April 2002
Chemical sensors going mobile
Buffalo, N.Y.—A new development has allowed scientists to take a major step toward placing hundreds of reusable chemical sensors in an area smaller than a dime.
This new development by researchers at the University of Buffalo could allow sensor technology to provide agricultural, clinical, environmental, and pharmaceutical laboratories with a small, fast, and portable methodology for simultaneously detecting numerous chemicals in a sample 100 or 1,000 times smaller than a drop of water.
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, such as a glass, but 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 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., associate chair and professor in the department of chemistry at UB’s College of Arts and Sciences.
The problem with traditional xerogel-based sensors is they are large and designed to detect only one chemical species, he said. 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.
Eun Jeong Cho, doctoral candidate in the UB department of chemistry, suggested pin printing, a technology widely used in genomics in which a thin pinpoint sucks up small volumes of solution and deposits or prints them onto microscope slides.
Using a commercial pin printer, just like those used in DNA microarray facilities, the UB team suddenly had a chemical sensor.
"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 working on pin printing chemical sensors on top of an LED to form a self-contained sensor array platform.