A miniaturised system for the measurement of the refractive index of sub-microlitre liquid
This study introduced the research into, and development of, a portable, miniaturised system for the measurement of the refractive index of sub-microlitre liquid based on a microfluidic chip. A technical method, namely, double-beam interference, was proposed for use in the measurement. Based on this, by using a laser diode as a light source, changes in refractive index were calculated by utilising a complementary metal-oxide-semiconductor (CMOS) to detect the movement of interference fringes of the liquid. Firstly, this study simulated the effects of influencing factors on the interference infringes of two Gaussian beams, such as their spot sizes, distance between two beam spots, and detection range. Secondly, this research introduced the system design and construction of the double-beam interference method and analysed the results of refractive index tests on sub-microlitre aqueous glucose solutions with different concentrations therewith. The measurement accuracy reached 10-4 RIU. This system has a compact structure and is rendered portable by using batteries for its power supply. The entire system is designed to be a double Z-shaped structure with a length of about 15 cm, a width of 5 cm, and height of about 10 cm: it can be used to measure changes in refractive index of sub-microlitre to nanolitre liquids based on the use of a microfluidic chip.
chen minghui,jia wenyu,he jintao,geiser martial,zheng gang. A miniaturised system for the measurement of the refractive index of sub-microlitre liquid[J].Chinese Optics Letters,2019,17(4):04.