Development of a multi-physics biofilm model incorporating biofilm mechanical and structural characteristics from multi-dimensional imaging datasets acquired by means of optical coherence tomography

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The objective of this project is to investigate in detail the influence of hydrodynamic and nutritional conditions on the mesoscale behavior of biofilm aggregates. By means of a unique combination of experimental and computational strengths, a comprehensive biofilm model will be developed that enables the reliable prediction of biofilm growth, architecture, interaction with the surrounding fluid, and detachment for a wide range of different conditions. Imaging techniques such as optical coherence tomography (OCT) for the mesoscale and confocal laser scanning microscopy (CLSM) for the microscale will provide the necessary information on biofilm development and internal structure at defined nutrient availability and hydrodynamic flow conditions. Oxygen sensitive optodes will provide information about the metabolic activity. These data will then be used for setting up and calibrating an advanced continuum biofilm model. Since biofilm material properties govern its behavior and interaction with the surrounding fluid, a thorough knowledge of the physical characteristics of biofilms is essential. Therefore, an imaging protocol will be developed, which will permit to visualize the biofilm structure at the mesoscale and characterize its properties by assessing the time resolved response of the biofilm to altered flow conditions in 3D. These experimental data will be transferred to the computational model by means of digital image processing and will then be the basis for the determination of biofilm material properties using an inverse analysis approach. Starting from the assumption of a homogeneous material, a (heterogeneous) distribution of biofilm properties will also be considered in the following to enable a more realistic modeling of biofilm behavior.As a next step, a reliable model for biofilm growth accounting for the different time scales involved will be developed. Again, a joint experimental-modeling effort is essential to identify relevant factors (e.g., nutrient availability and mechanical stress) and quantify their effect on biofilm growth. To estimate the cohesive and adhesive strength of the biofilm, detachment experiments will be conducted. This information will again be utilized for further development and calibration of the computational model.The quality of the resulting biofilm model including fluid-structure interaction (FSI), substrate transfer, growth, and detachment will be assessed by comparing simulated and experimentally observed biofilm structures. In particular, the predictive capability of the model will be evaluated by applying it to unknown scenarios such as real waste water biofilms or altered hydrodynamic loading. The model will then be utilized to gain more insights into mesoscale biofilm dynamics for a wide range of different conditions not necessarily realized experimentally. By these means, first steps towards systematically developing strategies for biofilm control/optimization will be taken.