Research On Light Propagation Property For Immunochromatographic Strip Based On Monte Carlo Method

Immunochromatographic optical biometric detection technology is based on the immunochromatographic test strip for the detection of objects,and it uses optical methods to obtain information on the optical markers on the test strip,resulting in the concentration of the biomass on the test strip.The study of the transmission of light in immunochromatographic test strips is,on the one hand,a scientific problem in the study of the transmission of photons in turbid media.On the other hand,it can provide theoretical support for the design of high performance immunochromatographic optical instruments.The immunochromatographic test paper is a light turbid medium,so Monte Carlo method can be used to simulate the photon scattering process.When using the Monte Carlo method to simulate the scattering behavior of photons,Craig F.Bohren et al analyzed different scattering models by electromagnetic radiation transmission theory,and give the scattering phase function of the particle model and the infinite cylindrical model.Alwin Kienle et al used the study of the scattering distribution of light in dentin to demonstrate the correctness of the infinite long cylindrical model.In this study,Monte Carlo simulation of bio-photonics is applied to explore the propagation laws of photons in immunochromatographic papers,thus providing a theoretical basis for the design of such optical biological detection instruments.It was observed under electron microscopy that the immunochromatographic test paper had a staggered porous structure composed of fibers and spherical particles,wherein the paper fibers had a diameter of 0.5 to 2 m and the fiber length was 10 times larger than the diameter.Therefore,the scattering model of the immunochromatographic test strip can be formed by the infinite straight cylindrical scattering model and the spherical particle scattering model(fiber-pellet model).In the Monte Carlo simulation,the scattering phase function of the spherical particles is approximated by Henyey-Greenstein phase function,and the phase function of the fiber is calculated from the scattering model of the infinite straight cylinder.The optical propagation characteristics of immunochromatographic paper were studied based on two kinds of scattering models,spherical partical model and infinite straight cylindrical mode.Furthermore,we explored the effects of various optical properties on the propagation characteristics and discussed how to improve the detection level of the immunochromatographic analyzer.In this paper,we studied the distribution of the intensity distribution of the scattering field on the outgoing surface of the fiber model and the spherical model,and gave the angular distribution of the scattered photons in the whole exit space.And the distribution of the peak position of the outgoing light at different incident angles along the normal direction and the distribution along the azimuth angle are obtained.Through simulation analysis,we come to a conclusion that,for a fiber distributed at a fixed spindle direction,the outgoing light is distributed in a plane perpendicular to the principal axis.