A patent is pending on the Planar Array IR (PA-IR) spectrograph developed by John Rabolt, chairperson of the Department of Materials Science and Engineering, and Mei-Wei Tsao, research professor in that department.

The device, which is now about the size of a large shoebox, can detect even small amounts of chemical weapons agents in solid, liquid or vapor phases.

It is also possible that the device can sense chemical agents at a distance, although Rabolt said further research on that is now being conducted. “We are planning to test the detectivity of our new PA-IR using a telescopic collection system that should be able to detect the presence of certain chemical agents at large distances away from our detector,” he said.

Using the analyte, or the compound that can be analyzed, that is specific to a given biological agent, the device can easily and quickly sense the agent’s presence. “Adding a series of such sensors near the at-risk sites could report back real-time findings via wireless transmitters,” Rabolt said.

Although its ability to detect chemical and biological weapons is of great interest given the recent terrorist attacks, the device also has broad industrial applications. It can be used to make real-time measurements of the thickness and chemical composition of various films, coatings and liquids.

“Our PA-IR system will enable companies that run production lines at extremely fast speeds to cut down on waste by keeping better track of imperfections or variations in product quality as it is being manufactured,” Rabolt said.

Advantages of the new UD system over other spectroscopy devices are high sensitivity, fast data acquisition and the absence of moving parts. “It is the latter that makes the PA-IR rugged, portable and reliable,” Rabolt said. “Its integrity is not compromised by aggressive environments.”

Rabolt and Tsao are working to further miniaturize the system to the size of a lunchbox and to expand its capabilities. The goal is to provide a generalized version for laboratory use and a specialized version for customized material sensing applications, such as industrial, military and environmental monitoring.

Rabolt said the invention resulted from the marriage of spectroscopy technologies from the 1960s with the high sensitivity detection technologies of the 21st century. He said “early spectroscopy devices were based on the use of light sources (lamps), the light from which could be broken into the various colors of the spectrum. Each material or substance absorbs a characteristic set of those colors providing a ‘fingerprint.’”

Because that process was lengthy and laborious, each color being broken down and applied one at a time, it was replaced by Fourier Transform spectroscopy, a multiplex technique based on inteferometry, which could record the entire color spectrum at once.

“The problem with such Fourier transform (FT) instruments,” Tsao said, “is the size and the required moving parts. FT-IR instruments use precision-machined mechanisms to facilitate the moving mirrors.

“In many cases, parts made by single-point diamond turning are required. The likelihood that such intricate machinery can survive portable application scenarios is low and that is why FT-IR has been confined to the laboratory environment for the most part.”

The UD design relies on an infrared light bulb and a focal plane array similar to a charge-coupled device, or CCD, which can be found in modern digital cameras.

The UD device “uses highly sensitive multi-element infrared detectors and can detect things that can’t be detected using Fourier transform spectroscopy, which employs single element infrared detection,” Rabolt said.

And, it can do that very quickly because of its fast data acquisition capability. Where it could take Fourier instruments on the order of hours to analyze an oil spill on the water—lost time that could have dire environmental consequences—the UD device can perform the same analysis in 30 seconds and can provide more accurate data.

In addition, the device is very simple in both design and construction. “We learned from years of instrumentation experience that the simpler the design is, the less likely things will go wrong,” Tsao said, adding, “One can easily envision a version of this device made with a single block of metal where all the metal junctions, such as welds and bolts, are removed.”

Funding for the research was provided, in part, by the National Science Foundation.