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Swell alcohol detector

May 31, 2001

A new, highly sensitive way of detecting alcohol vapour is published today in the Institute of Physics journal, Measurement Science and Technology. Researchers from the University of Yamanashi and the TRI Chemical Laboratory Inc in Japan have designed and tested new plastic optical fibre sensors that could be used to detect hazardous gas leaks, monitor the atmosphere in a brewery or even test for drivers who have drunk more than the legal alcohol limit.

Alcoholic chemicals such as methanol and ethanol are used in a variety of industries such as perfumes and plastics. However, pollution caused by such organic gases and solvents is a serious problem. Human health can be threatened if liquid or gaseous ethanol or methanol leak into the ground, and consequently into rivers and water supplies. Both methanol and ethanol are toxic and explosive, but also have many advantages as industrial raw materials. Methanol use could soon be greatly increased as developments are already underway for a methanol based fuel cell. It is therefore highly desirable to have a quick and sensitive way of detecting chemical leaks.

Knowing that a particular polymer called Novolac swells when exposed to alcohol molecules, resulting in a change in its refractive index, Dr Morisawa Masayuki and his team coated a standard plastic optical fibre sensor head in Novolac-resin and a Novolac complex (Novolac/Fe:SO complex). After exposure to saturated methanol vapour, the refractive index, which affects the angle of light passing through the fibre, decreased. Using this effect, a sensitive plastic optical fibre capable of detecting alcohol vapour has been developed.

Their experiments also showed that the Novolac complex had a greater effect than the Novolac-resin, owing to its black colour - black absorbs more light than other colours, so the initial light intensity through the sensor head is weak making the sensor sensitivity higher.
"This alcohol sensor has many advantages such as low costs, ease in handling and good flexibility. This makes it useful for many practical applications including a gas leak detector, atmospheric monitoring in a brewery or even a simple optical device for testing for drunk drivers," said Dr Morisawa.


Institute of Physics