Finite element simulation of antigen-antibody transport and adsorption in a microfluidic chip

The kinetics of antigen-antibody binding reaction, in the electrokinetically controlled microfluidic heterogeneous immunoassays, have been numerically simulated and discussed. The aim of this study is to demonstrate how to model phenomena defined in different 2D and 3D dimensions in a fully coupled manner using COMSOL Multiphysics. Moreover, we explain how to examine a convection-diffusion phenomenon present in a 2D domain (respectively 3D) coupled to diffusion-reaction phenomenon which is occurring only on a 1D boundary of this same area (respectively 2D). In our developed model, microfluidic networks for surface immunoassays were used. Antibodies, immobilized on one wall of a microchannel, absorb the employed analytes. The reaction rates in the modification area function of the reactants' concentration in the phase that transports the chemicals. Nevertheless, for surface reactions it is necessary to highlight the surface concentrations of the active sites and surface adsorbed species. The obtained results show that the increase of the concentration can reduce the growth of the diffusion boundary layer and raise the biosensor performance. Finally, the 2D simulations are described as crucial in predicting more accurate results.