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Research Papers

A Porous Elastic Model for Bacterial Biofilms: Application to the Simulation of Deformation of Bacterial Biofilms Under Microfluidic Jet Impingement

[+] Author and Article Information
Leo Y. Zheng

Mechanical Engineering Department,  Binghamton University-SUNY, Binghamton, NY 13902lzheng1@binghamton.edu

Dylan S. Farnam

Mechanical Engineering Department,  Binghamton University-SUNY, Binghamton, NY 13902farnam@binghamton.edu

Dorel Homentcovschi

Mechanical Engineering Department,  Binghamton University-SUNY, Binghamton, NY 13902homentco@binghamton.edu

Bahgat G. Sammakia

Mechanical Engineering Department,  Binghamton University-SUNY, Binghamton, NY 13902bahgat@binghamton.edu

J Biomech Eng 134(5), 051003 (May 25, 2012) (7 pages) doi:10.1115/1.4006683 History: Received September 30, 2011; Revised March 28, 2012; Posted May 01, 2012; Published May 25, 2012; Online May 25, 2012

The presence of bacterial biofilms is detrimental in a wide range of healthcare situations especially wound healing. Physical debridement of biofilms is a method widely used to remove them. This study evaluates the use of microfluidic jet impingement to debride biofilms. In this case, a biofilm is treated as a saturated porous medium also having linear elastic properties. A numerical modeling approach is used to calculate the von Mises stress distribution within a porous medium under fluid-structure interaction (FSI) loading to determine the initial rupture of the biofilm structure. The segregated model first simulates the flow field to obtain the FSI interface loading along the fluid-solid interface and body force loading within the porous medium. A stress-strain model is consequently used to calculate the von Mises stress distribution to obtain the biofilm deformation. Under a vertical jet, 60% of the deformation of the porous medium can be accounted for by treating the medium as if it was an impermeable solid. However, the maximum deformation in the porous medium corresponds to the point of maximum shear stress which is a different position in the porous medium than that of the maximum normal stress in an impermeable solid. The study shows that a jet nozzle of 500 μm internal diameter (ID) with flow of Reynolds number (Re) of 200 can remove the majority of biofilm species.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of axisymmetric impingement on a biofilm: water jetted from a circular cross-section nozzle impinges on the biofilm. It is simplified into a two-dimensional problem and only the right half is studied due to its symmetry.

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Figure 2

Nondimensionalized shear stress on an impermeable surface as a function of distance from the stagnation point compared with the study of Deshpande and Vaishnav

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Figure 3

Pressure along the impermeable interface versus pressure as a function of radial distance from the jet center in various heights within the porous solid (ID = 500 μm, Re = 25)

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Figure 4

Shear stress along the fluid-solid interface in the impermeable case versus shear stress along the fluid-solid interface in the porous medium case (ID = 500 μm, Re = 25)

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Figure 5

Interface displacement comparison between impermeable interface and porous interface (ID = 500 μm, Re = 25)

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Figure 6

Flow speed along the line 10 μm above the biofilm interface comparing the flow speed along the half height line within the biofilm (ID = 500 μm, Re = 25)

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Figure 7

von Mises stress as a function of radial distance from the jet center along the top, middle, and bottom of the porous biofilm (ID = 500 μm, Re = 100)

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Figure 8

Stress concentration occurring around the initial cavity (ID = 500 μm, Re = 100)

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Figure 9

Remaining biofilm after the biofilm that is subjected to von Mises stress above its yield stress and therefore removed under the stronger jet (ID = 500 μm, Re = 100)

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Figure 10

von Mises stress calculated from the numerical modeling as a function of Reynolds number representing the strength of the jet impingement of three different nozzle sizes (ID = 500 μm, ID = 250 μm, and ID = 125 μm) is compared with the experimental results of detachment strengths for Streptococcus mutans biofilm (Kreth [21]), Osteoblastic cells (Giliberti [23]), L929 fiberblast (Bundy [20])

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