Lattice Boltzmann Simulation On Liquid Percolation In Diffusion Layer Of In-Vitro Diagnostic Chips

In-vitro diagnostic chips are easy to carry and operate,which have the advantages of"fast,convenient,accurate",etc.to realize point of care testing(POCT).Under the promotion of"hierarchical diagnosis and treatment"and other policies,the market is expanding rapidly,and the prospective is widening.The rapid and efficient detection of in-vitro diagnostic chips are inseparable from the effective percolation and dispersion of liquid in diffusion layer and reagent layer.In this paper,the Lattice Boltzmann Method was used to simulating the percolation and dispersion of liquid in diffusion layer of in-vitro diagnostic chips,and the flow process between diffusion layer and reagent layer.Basic data can be provided for the selection and design of diffusion layer in practical application,which has better practical application value and significance.Based on the mathematical model established by the Lattice Boltzmann Method,the influencing factors of controlling flow time were analyzed.The results showed that the microsphere diameter,the properties of liquid and the surface properties of diffusion layer material were the main factors affecting liquid percolation in in-vitro diagnostic chips.The larger the particle diameter is,the faster the liquid percolation is.The wettability of materials was increased,and the kinematic viscosity of liquid was reduced appropriately will also promote the percolation.Among the above factors,the microsphere diameter has a great influence on the percolation characteristics in in-vitro diagnostic chips,while the surface properties of materials have the second influence on the percolation,and the properties of liquid have a little influence on the percolation.By fitting about 12 groups of the calculation results of Lattice Boltzmann model,the empirical formula of quadratic linear model of the velocity changing with microsphere diameter,liquid-solid contact angle and kinematic viscosity was obtained.The empirical formula of quadratic linear model can be used by chip designers to calculate the appropriate diffusion layer microsphere materials and particle diameters.Furthermore,the liquid flow process between diffusion/reagent layer of in-vitro diagnostic chips was simulated by the Lattice Boltzmann Method.The conditions of liquid blocking at capillary ports or flowing into capillaries in reagent layer were analyzed.The influence of the diffusion layer thicknesses on the liquid flow process in reagent layer was also investigated,and the curve of the relationship between the diffusion layer thicknesses and the droplet diameters at capillary ports was fitted when the diffusion layer materials were polystyrene and Ti O₂.The results showed that the diffusion layer thickness was not conducive to the smooth flow of liquid into capillaries of reagent layer when the thickness is too large or too small.On the premise that liquid can flows into the capillary,the increasing diffusion layer thicknesses will prolong the dispersion time of liquid and reduce the droplet diameters at capillary ports and the speed of flowing into capillaries.The empirical formula of fitting curve obtained by simulation can be used for designers to quickly select the data of the diffusion layer thicknesses.