New sensor detects biological and chemical agents

Researchers at the University of Delaware have developed a portable detection platform that could provide real-time recognition of chemical and biological weapons using infrared spectroscopy.

The Planar Array IR (PA-IR) spectrograph, developed by John Rabolt and Mei-Wei Tsao, can reportedly detect even small amounts of chemical weapons agents in solid, liquid or vapour phases.

Using the analyte that is specific to a given biological agent, the device can 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.

Advantages of the new UD system over other spectroscopy devices are said to be 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 miniaturise the system, which is currently the size of a shoebox, to the size of a lunchbox and to expand its capabilities. The goal is to provide a generalised version for laboratory use and a specialised version for customised 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 colours of the spectrum. Each material or substance absorbs a characteristic set of those colours providing a ‘fingerprint.”

Because that process was lengthy and laborious, each colour 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 colour 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 hours to analyse an oil spill on the water the UD device can perform the same analysis in 30 seconds and can provide more accurate data.