Researchers Complete First Step In Creation Of Smaller Chemical Sensors

November 24, 1997

ATHENS, Ohio -- Ohio University scientists have developed a new compression method that will enable computers to store millions of data points in just 1 percent of the disk space presently required. While the technique has applications throughout the computer industry, the creators will use it in the design of a stamp-sized sensor to detect toxic chemicals in the air.

Federal regulations require employers to monitor workers' exposure to organic chemicals, but current sensors are bulky, limited in how much data they can store and lack the technology to identify chemicals they detect.

Chemistry researchers in Ohio University's Center for Intelligent Chemical Instrumentation are developing a smaller, intuitive sensor that could be used on the job site and in the home, said Peter Harrington, associate professor of chemistry and co-author of the study.

"The sensors we use today are about the size of a TV remote, and they are limited in their ability to store and analyze data. Other portable sensors don't work at the regulatory limits and prevent industry and government from compliance with chemical exposure restrictions enforced by the Occupational Safety and Health Administration and the Environmental Protection Agency," Harrington said.

Conventional chemical sensors detect ions in the air, but lack the ability to specify which chemicals have been recorded, he added. While a worker could be alerted that a chemical is present, there is no way of knowing if the exposure is within acceptable levels or if the substance is nonthreatening.

"Our goal is to allow workers to know what chemical is in the air around them and how much is there, so that they can be alerted of possible dangers," he said.

For a chemical sensor to be effective, it must be able to store large amounts of information indefinitely in a way that allows for quick access to the data, which has been the challenge to chemists and engineers working on the problem.

"The important thing about our method is that no information is lost," Harrington said. "People who will use these sensors in the workplace have told us they need to be able to store the information indefinitely. They want to be able to track a worker's exposure to organic chemicals, and that means the computer must be able to store a tremendous amount of information. But at the same time, sensors need to be smaller and easier to wear. That's why compressing the data is helpful."

Most sensors collect and store data with respect to time -- the amount of recording time and the time it takes certain ions to arrive at the detector. This method can be problematic, Harrington said, because the sensor records all time-dependent signals, even those that represent useless information. Ohio University researchers used a Fourier transform -- a mathematical formula that converts time-dependent signals to spectra that correspond with specific frequencies. This allows the scientists to filter out unwanted information found at certain high frequencies.

"Storing information with respect to time means that a lot of high-frequency information, which is usually noise, is recorded. That information isn't used and takes up valuable disk space," Harrington said. "By going to a frequency representation, we were able to eliminate a lot of empty space to make room for more valuable data."

Sensors developed through this U.S. Army-funded project also could be used in the home to detect chemicals such as benzene, which can be released from paint thinner, and formaldehyde, which leaches from new carpet and plastic used in home and other building construction. These substances have been linked to "sick building syndrome," implicated in some occupation-related illnesses.

The study, published in a recent issue of the American Chemical Society journal Analytical Chemistry, was co-authored by Cheunsheng Cai, a chemistry doctoral student at Ohio University, and Dennis Davis, a chemist with the U.S. Army.

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Contact: Peter Harrington, 614-593-2099;
Written by Kelli Whitlock, 614-593-0383;

Ohio University

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