The Impact of Biofilm Permeability and Porosity on Dynamic Changes in Flow Paths in Porous Media

ABSTRACT This study observes the evolution of Bacillus subtilis biofilm in two microfluidic channels containing nonuniform and uniform porous medium, revealing dynamic changes in flow paths (areas without biofilm). In the nonuniform porous medium, flow paths shift towards macropore throat regions: The qualitative form of flow paths remains unchanged, but their overall positions undergo displacement; while in the uniform porous medium, flow paths undergo reorganization: After clogging, the new flow path suddenly opens, manifested as significant changes in geometry and position. By inputting digital images obtained from microscope images, we use mathematical modeling to study the effects of biofilm permeability (k b ) (from 10 −15 to 10 −9 m 2 ) and porosity (ε b ) (from 0.1 to 0.9) on dynamic changes in flow paths. The simulation results indicate that the physical properties of biofilms affect the flow in porous media, and nonuniform porous medium induces the formation of more impermeable biofilm structures. With the decrease in biofilm permeability, the boundary shear stress along the flow paths increases, and the position of the boundary migrates towards the macropore throat regions. When porous media are clogged by low‐permeability biofilms, a greater pressure difference is generated, making it easier to form new flow paths. Furthermore, increasing the porosity of low‐permeability biofilms has no significant effect on the flow in porous media. High‐permeability biofilms experience greater internal shear stress, leading to the detachment of regions with low cohesive strength and the formation of new flow paths.