Computational Investigation of Ripple Dynamics in Biofilms in Flowing Systems

Abstract

Biofilms are collections of microorganisms that aggregate using a self-produced matrix of extracellular polymeric substance. It has been broadly demonstrated that many microbial infections in the body, including dental plaque, involve biofilms. While studying experimental models of biofilms relevant to mechanical removal of oral biofilms, distinct ripple patterns have been observed. In this work, we describe a multiphase model used to approximate the dynamics of the biofilm removal process. We show that the fully nonlinear model provides a better representation of the experimental data than the linear stability analysis. In particular, we show that the full model more accurately reflects the relationship between the apparent wavelength and the external forcing velocities, especially at mid-to-low velocities at which the linear theory neglects important interactions. Finally, the model provides a framework by which the removal process (presumably governed by highly nonlinear behavior) can be studied.

Computational and Experimental Investigation of Biofilm Disruption Dynamics Induced by High-Velocity Gas Jet Impingement

“…The Herschel-Bulkley parameters of the estimated biofilm viscosity curve EVC 3 described the required shear-thinning behavior, with the fitted yield stress ( y ϭ 0.745 Pa) in accordance with the viscoelastic linearity limit ( ϭ 3.5 Pa) previously determined by creep analysis (28). Biofilms in general show mechanically viscoelastic behavior (38,39); however, the consistent results obtained considering the biofilm as a non-Newtonian fluid indicate that under turbulent flows, the biofilms elastic behavior can be neglected, as recently reported (22). Additionally, biofilm expansion under noncontact brushing is attributed to its viscoelastic nature (41).…”

“…Small biofilm deformations have also been modeled considering the biofilm as a poroelastic material, compressing when exposed to laminar flows (20,21). The effect of parallel air-water jets on the surface morphology of very viscous biofilms has been investigated numerically (3,22), proposing the characterization of the biofilm rippling as Kelvin-Helmholtz instability. However, the interactions between biofilm and perpendicular impinging turbulent jet flow and how the turbulent impacts disrupt biofilm properties have not yet been described numerically.…”

Structure and resistance to mechanical stress and enzymatic cleaning of Pseudomonas fluorescens biofilms formed in fresh-cut ready to eat washing tanks.

“…However, such elongated shape clusters were also observed for biofilms formed in vats in every area largely affected by the flow recirculation induced by the impeller, either on bend zones (with welds or not), or simply on vertical and horizontal surfaces. Such a pattern is different from the ripple-shaped pattern (perpendicular to the flow) described by (Cogan et al, 2018), taking into account the oscillatory phenomenon induced by the flow. In addition to the morphology, hydrodynamics affects cell density and biofilm matrix composition.…”

Bayesian estimation of Pseudomonas aeruginosa viscoelastic properties based on creep responses of wild type, rugose, and mucoid variant biofilms

“…Biofilms are subject to a wide range of shear forces over many magnitudes of time scales, many too short or too long for lab experimental test methods. Examples of these are high-speed interactions with water jets, such as interdental cleaning jets or pulse lavage in the wound and surgical site debridement as well as pressure washing of industrial surfaces such as ship hulls [ 48 , 49 ]. On the other hand, biofilms in the natural environment or on industrial surfaces are exposed to fluid forces over days to weeks to decades, impacting industrial performance.…”

“…Understanding the underlying structure of biofilm and its impact on rheological properties provides novel directions to explore biofilm removal. For example, many biofilm removal techniques rely on applying forces to the biofilm to force sloughing [ 49 ]. By applying specific treatments that target different constituents, we can enhance this removal by manipulating the rheological properties.…”