Research And Application On Optofluidics-based Rapid Detection By Free-space Young Interferometer

High-resolution micro-scale chemical analysis techniques are playing a significantly important role in chemical and biological analysis.The refractive index as an inherent property of the liquid itself can reflect the internal nature of the liquid.Refractometer can measure the refractive index of the sample solution in a sample cell by monitoring the difference in refractive index of the solution in the reference cell and the sample cell.However,the Refractometers currently on the market are mostly based on refractive-type and planar optical waveguide interferometers.Among them,the accuracy of the refractometers is easily affected by the external temperature,air pressure,and sample density,and the environment is more demanding.Refractometers based on planar optical waveguide interferometry also have high sensitivity with changes in ambient temperature and require pre-treatment of the sample and microfluidic channel surfaces prior to biological sample measurement.The cycle to complete a measurement is too long（it will take several hours to 24 hours）,and it is almost impossible to measure biomolecules of unknown aptamers or biomolecules that cannot be modified to immobilize on the surface.In addition,it is difficult to realize the integration and miniaturization of analytical instrumentsTherefore,in this paper,we designed a refractometer based on the microfluidic chip technology and spatial Young’s interference technology to realize the measurement of the refractive index of the solution without labeling in a free solution.The specific work is as follows:1.The refractometer system based on microfluidic chip technology and spatial Young’s interference technology mainly included light source,microfluidic system,fluid control system and signal acquisition system.We chosed the He-Ne laser as the light source;We prepared a glass-based microfluidic chip.The two-channel microfluidic chip had a 2 mm channel spacing,a 200 um channel width,and a 50 um channel depth.we used CO₂laser to perforat in quartz glass.A double slit with a pore size of 150 um and 2mm pitch was made on the substrate as Young’s double slit;a syringe pump was used as the fluid control system;we choosed 1×2048 linear array CCD which the pixel size was 14 um,the bit was 16 as image acquisition system.2.We established an optical interference model based on MATLAB,simulate the parameters of the refractometer,got the optical interference in the CCD imaging simulation,and used the fast Fourier transform method to obtain the accuracy of the CCD detection interference phase difference change.we changed Different CCD parameters to select the optimal parameters of the CCD,and finally the optimal parameters of the image sensor CCD:the pixel size is14um,the bit depth is 16.Without considering various noises,the accuracy of the phase detection accuracy was 3.4×10×2πrad3.The NaCl solution with different concentrations as the actual sample was tested by the established Refractometer system.The accuracy of the refractive index detection was 10^-5RIU.