Valencia (Spain) - A team of research scientists have discovered a way to replace a very expensive laboratory device with only a slightly modified CD drive. The result of the mod? An inexpensive, portable laboratory scanner suitable for detecting various chemical compounds.
Angel Maquieira, a researcher at Polytechnic University of Valencia, Spain, said the standard light detection machines used in scientific laboratories often cost 30K - 60K Euros. This makes them unsuitable for large scale portable use. And while the modified CD drive turned portable chemical scanner this team has come up with is not quite as fast as the dedicated device, it has been shown to detect pesticides at concentrations as low as 20 nanograms per liter, making it accurate enough for many routine lab tasks.
The system works using the same basic techniques typically used in today's dedicated devices. For example, when detecting a chemical pollutant in a water medium, a type of dye or doping agent is added which changes the sample's color through a chemical reaction. These results would then read by a light sensing device to categorize its concentration. In the case of the modified CD drive, the material is placed on the surface of a regular compact disc in standard track layout and read as it spins slowly around.
The basic CD-ROM drive has been modified with two additional light sensors. The first is used to determine the "track" the sample is sitting on. The second measures the reflected light intensity. CD discs typically reflect only about 30% of their light back to the sensor. So, by modifying the chemical doping agent to have a silvery, reflective surface (instead of just a color) the amount of light being reflected back can be read. This is then used to determine the concentration.
In field tests, tiny dot test samples are placed on the disc and read one by one. By spinning the CD slowly, and by measuring the light returning to the sensor up to 3072 dots can be processed today. By extending their design the same researchers believe more than 10,000 samples per CD could be achieved.
Previous researchers have taken the read head from a CD-ROM drive and used it in specially created devices for achieving the same results. By using the whole CD-ROM drive, the Spanish team has been able to demonstrate viability from off-the-shelf components with high accuracy and very low cost. The team also hopes to find future uses for Blu-ray and HD-DVD drives which use finer laser beams, potentially capable of even greater precision, accuracy sample capacity and speed.