This research is dedicated to the development and simulation of a new model of biofilm dynamics. Specifically, the model includes comprehensive fluid dynamics for a fluid flowing over a generic biofilm domain. The major advance in this model is to allow for the motion of the biofilm due to the fluid motion and growth processes. The biofilm is composed of multiple species of bacteria that consume multiple types of nutrients and produce both bacteria and exo-polymeric substance (EPS). The EPS is responsible for the redistribution of the biomass by virtue of the osmotic pressure that typifies hydrogels. By producing EPS in regions of higher nutrient concentration, gradients of EPS concentration are set up. These gradients induce a force on the biofilm tending to equilibrate the concentration of EPS. This physical description of biomass redistribution coupled with realistic motion of the biofilm due to growth is a substantial improvement over existing models. Much of the focus of the early investigations will concern numerical methods to incorporate the free boundary that marks the permanent separation between the bulk fluid and the biofilm regions. The methods that we are using are based on boundary integral methods that have been used successfully to model two fluid systems with various types of boundaries (e.g. elastic, passive). To use these methods, a generalized reciprocal theorem will be derived which includes the growth of the biofilm in the constitutive relationship. Once the reciprocal theorem is established, an integral equation can be derived that determines the velocity of the fluid/biofilm system.
Microbial biofilms have a significant impact on virtually all areas of our lives. While these impacts can be beneficial, such as the use of biofilms in bioremediation and wastewater treatment, the majority of current research focuses on the detrimental processes associated with biofilm contamination. Negative impacts of biofilms include examples from such diverse areas as food service industries, chemical manufacturing plants, paper production plants and various medical settings. These impacts include increased cost, lowered efficiency, increased corrosion, fouling and increased impurities and infections. Realistic models of biofilm growth and development will aid experimentalists in proposing new experimental inquiries. Also, because detailed spatial data can be generated from model simulations more readily than by experimentation, novel hypotheses of persistent formation and detachment can be proposed based on values of concentrations and internal stresses.
