Currently in forensic investigations the presence of illicit drugs is analyzed via a colour test. In this test the presumed illegal substance (mostly a powder) is dissolved and mixed with a reagant that changes color upon reaction with a specific compound. The analysis is done with the naked eye, on the basis of a color chart, and gives a yes-no answer on the detection of a drug. Modern microfluidic technology in combination with miniaturized spectroscopic techniques would allow to extract much more information from a sample, because it is possible to do sample mixing and reaction in a closed environment (a microfluidic chip) in a portable system which includes a possibility for optical detection, via a laser or a LED and a photodetector.
Some preliminary research has already been performed on a microfluidic chip which was designed with a compartment with a long optical path for light absorption, and a fixture for alignment of optical fibers for illumination and detection of UV-Vis absorption. An existing problem with the drug colour test is that most of the well-known tests give a precipitate, which can block the microfluidic channels, but also can interfere with the light passing through the optical cell. It is not sufficient to filter the solid deposit from the solution, because it is actually the color of the deposit that is indicative of the presence of the drug. This color cannot be determined via absorption because the deposition of the solid is uncontrolled.
The goal of this assignment is to redesign the complete system in order to have:
- controlled deposition of the solid, which means that the solid should deposit uniformly over a defined wall surface; one option could be to use a centrifugal principle;
- an optical element for color measurement of the deposit, either via absorption or via reflection
Furthermore, the goal is to fabricate the system and test it with an existing color test.
Han Gardeniers; Email: email@example.com