Nanotubes signal when engine oil needs changing.A new, easy-to-fabricate sensor made from carbon nanotubes detects when automobile-engine oil needs replacement. As a car is driven, its lubricating oil undergoes chemical reactions with air and with combustion by-products. Those reactions degrade the oil--for instance, by causing chemicals known as hydroperoxides hy·dro·per·ox·ide (h ![]() dr -p -r to build up. In previous work, other researchers had observed that carbon nanotubes become more electrically conductive when exposed to hydroperoxides. In the new study, Seung-Il Moon of Korea University in Seoul and his colleagues blended nanotubes with glue and then printed a thin layer of the mixture onto a glass-and-metal backing to make a microchip-size sensor. They then attached the sensor to an engine dipstick dipstick /dip·stick/ (dip´stik) a strip of cellulose chemically impregnated to render it sensitive to protein, glucose, or other substances in the urine. and inserted it into the oil reservoir of a ear. Electrical measurements showed a steady increase in current through the sensor as the car was driven 6,000 kilometers, the team reports in the August Electrochemical and Solid-State Letters. Additional laboratory tests indicated that changes in conductivity closely matched variations in a chemical signature known as total acid number, a sign of oil quality. The team is continuing work on the sensor with a Korean automaker. |
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