Predicting biofilm deformation with a viscoelastic phase‐field model: Modeling and experimental studies

Abstract

Biofilms commonly develop in flowing aqueous environments, where the flow causes the biofilm to deform. Because biofilm deformation affects the flow regime, and because biofilms behave as complex heterogeneous viscoelastic materials, few models are able to predict biofilm deformation. In this study, a phase-field (PF) continuum model coupled with the Oldroyd-B constitutive equation was developed and used to simulate biofilm deformation. The accuracy of the model was evaluated using two types of biofilms: a synthetic biofilm, made from alginate mixed with bacterial cells, and a Pseudomonas aeruginosa biofilm. Shear rheometry was used to experimentally determine the mechanical parameters for each biofilm, used as inputs for the model. Biofilm deformation under fluid flow was monitored experimentally using optical coherence tomography. The comparison between the experimental and modeling geometries, for selected horizontal cross sections, after fluid-driven deformation was good. The relative errors ranged from 3.2 to 21.1% for the synthetic biofilm and from 9.1 to 11.1% for the P. aeruginosa biofilm. This is the first demonstration of the effectiveness of a viscoelastic PF biofilm model. This model provides an important tool for predicting biofilm viscoelastic deformation. It also can benefit the design and control of biofilms in engineering systems.

Biofilm viscoelasticity and nutrient source location control biofilm growth rate, migration rate, and morphology in shear flow

“…For large-scale simulations of biofilm processes, continuum models are utilized to simulate the fluid flow, nutrient distribution, and the spatial expansion of biomass. Examples include phase-field approaches that simulate the growth of non-elastic viscous biofilms 39 or the deformation of viscoelastic biofilms that do not grow 40 . Even though these continuum models can produce results that match elaborate experiments quantitatively, their formulations tend to be complicated and computationally challenging 22 .…”

Spatial distribution of mechanical properties in Pseudomonas aeruginosa biofilms, and their potential impacts on biofilm deformation

“…Mathematical models describing biofilm mechanical behavior can improve our understanding of biofilm structures and properties (Böl et al, 2012). Such models include the simulation of biofilm deformation under applied stress (Li et al, 2020;Picioreanu et al, 2018;Picioreanu et al, 2001;Towler et al, 2007). However, the mechanical properties are typically assumed to be homogeneous and are based on large-scale measurements.…”

Data‐driven modeling of heterogeneous viscoelastic biofilms

“…OCT has been used to study biofilm thickness, roughness, and other morphological characteristics (Aybar et al, 2019;Shen et al, 2016;Wagner et al, 2010). Biofilm geometry and deformation can be extracted from OCT images, and mechanical properties inferred by combining those with biofilm deformation models (Blauert et al, 2015;Li, Matouš, et al, 2020;Picioreanu et al, 2018). In a recent study, OCT was applied to granular biofilms for the consideration of layered viscoelastic properties (Liou et al, 2021).…”

“…Since the mechanical properties of biofilms are largely dependent on cell density (Kwok et al, 1998;Van Loosdrecht et al, 2002), OCT images can be a useful tool to map effectively biofilm mechanical properties. In our study, a 2D map of biofilm mechanical properties (i.e., the non-Newtonian (Li, Matouš, et al, 2020).…”