CD players turned to chemical detectors

Spanish scientists have tinkered with an ordinary computer CD drive, turning it into a chemical testing platform that can detect the presence of different pesticides. All they did was to solder a couple of light sensors inside a CD player, utilizing software to control the way the device “plays” a disk.

The first sensor identifies the sector of a disk containing a sample using black marks on the edge of the disk. The second analyses the sample itself, measuring the amount of laser light that is able to pass through the disk. Ordinary disks normally reflect around 30% of the laser beam onto the reading head, with the rest passing through.In experiments, the researchers used their modified drive to detect traces of three different pesticides. A sample – half a millimetre across on a disk – was treated normally, using a set of reactions that produce an amount of dye or silver that is inversely proportional to the amount of pesticide in the sample. The amount of laser light that passed through the disk to the second sensor indicated the levels of dye or silver. The modified drive was thus able to detect levels of pesticide as low as 0.02 micrograms per litre.

Despite the fact that this device is pretty crude, it is still accurate enough for many lab tasks. Hopefully next generation DVD players will yield better results with the same treatment.