Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands.
Water Chemistry and Water Technology, Engler-Bunte-Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany.
Water Res. 2018 Nov 15;145:588-598. doi: 10.1016/j.watres.2018.08.070. Epub 2018 Sep 1.
The advantage of using non-invasive imaging such as optical coherence tomography (OCT) to asses material properties from deformed biofilm geometries can be compromised by the assumptions made on fluid forces acting on the biofilm. This study developed a method for the determination of elastic properties of biofilms by modelling the biofilm deformation recorded by OCT imaging with poroelastic fluid-structure interaction computations. Two-dimensional biofilm geometries were extracted from OCT scans of non-deformed and deformed structures as a result of hydrodynamic loading. The biofilm geometries were implemented in a model coupling fluid dynamics with elastic solid mechanics and Darcy flow in the biofilm. The simulation results were compared with real deformed geometries and a fitting procedure allowed estimation of the Young's modulus in given flow conditions. The present method considerably improves the estimation of elastic moduli of biofilms grown in mini-fluidic rectangular channels. This superior prediction is based on the relaxation of several simplifying assumptions made in past studies: shear stress is not anymore taken constant over the biofilm surface, total stress including also pressure is accounted for, any biofilm shape can be used in the determinations, and non-linear behavior of mechanical properties can be estimated. Biofilm elastic moduli between 70 and 700 Pa were obtained and biofilm hardening at large applied stress due to increasing flow velocity was quantified. The work performed here opens the way for in-situ determination of other mechanical properties (e.g., viscoelastic properties, relaxation times, plastic yields) and provides data for modelling biofilm deformation and detachment with eventual applications in biofilm control and removal strategies.
使用非侵入性成像（如光学相干断层扫描 (OCT)）来评估变形生物膜几何形状的材料特性的优点可能会受到作用于生物膜的流体力的假设的影响。本研究通过用多孔弹性流固相互作用计算来模拟 OCT 成像记录的生物膜变形，开发了一种确定生物膜弹性特性的方法。二维生物膜几何形状是从非变形和变形结构的 OCT 扫描中提取的，这是由于流体动力加载的结果。生物膜几何形状被实现为一种模型，该模型将流体动力学与弹性固体力学以及生物膜中的达西流耦合。将模拟结果与真实变形几何形状进行比较，并通过拟合程序允许在给定的流动条件下估计杨氏模量。本方法极大地提高了在微型流体矩形通道中生长的生物膜的弹性模量的估计。这种优越的预测是基于对过去研究中做出的几个简化假设的放松：生物膜表面上的剪切应力不再保持恒定，包括压力在内的总应力被考虑在内，可以使用任何生物膜形状进行测定，并且可以估计机械性能的非线性行为。获得了 70 到 700 Pa 之间的生物膜弹性模量，并量化了由于流速增加而导致的大施加应力下的生物膜硬化。这里进行的工作为原位确定其他机械性能（例如粘弹性特性、弛豫时间、塑性屈服）开辟了道路，并为生物膜变形和脱落的建模提供了数据，最终可应用于生物膜控制和去除策略。
