An experimentally validated immersed boundary model of fluid-biofilm interaction.

Biofllms are colonies of microorganisms that live on wetted surfaces in a matrix consisting of polysaccharides, proteins, and nucleic acids. According to the National Institute of Health (NIH), biofilms play a role in over 80 percent of microbial infections in the body and these infections are remarkably difficult to treat with antimicrobial compounds. The objective here is to understand and predict the physical interaction between a biofilm and the surrounding fluid flow. We have developed a biofilm-fluid interaction model, based on the Immersed Boundary Method, to simulate the interaction between the biofilm and a moving fluid. The model predictions of biofilm deformation quantitatively agree with experimental measurements for a range of biofilms using a simple immersed elastic solid to model the biofilm matrix. An immersed viscoelastic solid model is also developed and compared with experimental measurements. The results show that the viscoelastic behaviour inherent in the immersed boundary method (even when using a simple immersed elastic solid) is sufficient for some biofilms, but a slightly viscoelastic solid gives more general agreement with experimental measurements.