The Mechanical Analysis of the Biofilm Streamer Nucleation and Geometry Characterization in Microfluidic Channels.

Xiaoling Wang,Mudong Hao,Jun-Ichi Matsushita,Guoqing Wang,Xin Du

doi:10.1155/2016/7819403

Abstract

Bacteria can form biofilm streamers in microfluidic channels with various geometries. Experiments show that the streamer geometry, such as its shape or thickness, depends on the fluid velocity and the geometry and curvature of the microfluidic channel. In the paper, a mechanical analysis of the flow field is made in different channels, which shows that the secondary flow in the channel is the reason for streamer nucleation and that the shear stress distribution decides the streamer geometry including shape and thickness. Through a finite elements simulation, we obtain the secondary flow forming positions in both static and rotating channels: positions that are the location of nucleation of the streamer. Thick or wide biofilm streamers occur at the points of minimum shear stress in static channels. Furthermore, in rotating channels, spiral-like streamers form, due to the helical shape of the minimum shear stress distribution. The findings may allow the prevention of biofilm formation and also the removal of bacteria adhered onto certain surfaces in channels with small cross sections. The analysis also indicates how one can obtain desirable biofilm streamers by control of the channel geometry and the loading conditions.

Highlights

Biofilms are natural structures formed by microbial communities encapsulated inside a matrix of self-secreted extracellular polymeric substances (EPS), growing most commonly on a solid surface [1, 2]
Rusconi et al observed biofilm streamer formation in the middle of channels with different corner shapes; the streamer initially formed at the corners and stayed connected only to the lateral walls while the rest of the streamer structure lay suspended in the flow, as shown in Figures 1(c) and 1(d) [12]
The results show that the secondary flow in the channel is the reason for biofilm streamer nucleation and that the shear stress distribution decides biofilm streamer geometry including its shape and thickness

Summary

Introduction

Biofilms are natural structures formed by microbial communities encapsulated inside a matrix of self-secreted extracellular polymeric substances (EPS), growing most commonly on a solid surface [1, 2]. Rusconi et al observed biofilm streamer formation in the middle of channels with different corner shapes; the streamer initially formed at the corners and stayed connected only to the lateral walls while the rest of the streamer structure lay suspended in the flow, as shown in Figures 1(c) and 1(d) [12]. The quantitative relationship between biofilm streamer structure and shear force distribution is lacking, pointing to the need for theoretical work and numerical simulation for a more complete understanding of streamer formation. The results show that the secondary flow in the channel is the reason for biofilm streamer nucleation and that the shear stress distribution decides biofilm streamer geometry including its shape and thickness

Theory

Numerical Simulation and Results

Discussion and Conclusion