Study On Photometric Absorbing Spectral Analysis In Micro-fluidic Chips

Micro-fluidic chip is the most flourish and develop fastest in the field of miniaturized total analysis system( u TAS). It demonstrates the excellent idea that focuses the total analyzing system into a small chip. On the Micro-fluidic chip, the detector is an important part; it will determine the limitation, speed, applying area and volume of the chip. For the need of biochemical chip, which consumes fewer specimens and is easy to integrate with micro-fluid chip, two kinds of spectrophotometric analysis methods, are described in this paper.The first method is based on schemes of direct absorption in which two gradual refraction index lens are hybrid integrated in the system. Its minimum optical path length limits it length in this direction. However, if we use two gradual refraction index lens which is very small, the length of the cuvette in other two directions can be small enough, base on this idea we can reduce the sample consumption a lot.The second one is a fiber evanescent sensor. It is obtained by removing a small length of the cladding of a commercial single mode fiber or multimode fiber and replacing by an absorbing medium. The evanescent field in the cladding interacts with the absorption medium surrounding the core and power transmitted by the fiber is attenuated. Comparing the variety of the spectrum before and after absorption, we can affirm the concentration of the sample.Both direct detection method and evanescent wave detection method are used to detect the spectral absorption of mixture of blood serum and BCG reagent. The light source is visible light(460~800nm). Comparing the results with standard instrument λ -9 photometer, it proved that the spectral analysis in micro-fluidic chips meets the needs of optical detection.The experimental results proved that direct detection is simple and evident; on the other hands evanescent wave detection method consumes reagent and easy to integrated on micro micro-fluidic chips.