Eduardo CesarThe CDs used to store data or music are the basis of a low cost sensor developed at the Chemistry Institute of the University of São Paulo, which can quickly detect if a sample of milk has been adulterated with hydrogen peroxide, or not. The research was done during the post-doctoral project of Thiago Longo Cesar da Paixão, on the development of electronic language. “Milk was chosen because of the problems faced last year”, he says. Hydrogen peroxide kills some bacteria and prolongs the shelf-life of the product, but consuming it can cause intestinal upsets. To manufacture the sensors the researcher used imported CDs with gold films that were exposed after removing the layers of polymer. A computer-produced drawing of the electrodes necessary for the device is made, printed on tracing paper and transferred to the CD’s gold layer by a heat process. The surface of the electrodes is covered with inorganic compounds and with the application of an electric current it is possible to analyze the milk by comparing the graphs produced with other standardized ones.
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