Optimal Design of Bacterial Carpets for Fluid Pumping

Minghao W Rostami,Eva Strawbridge,Longhua Zhao,Amy Buchmann,Weifan Liu

doi:10.3390/fluids7010025

Abstract

In this work, we outline a methodology for determining optimal helical flagella placement and phase shift that maximize fluid pumping through a rectangular flow meter above a simulated bacterial carpet. This method uses a Genetic Algorithm (GA) combined with a gradient-based method, the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, to solve the optimization problem and the Method of Regularized Stokeslets (MRS) to simulate the fluid flow. This method is able to produce placements and phase shifts for small carpets and could be adapted for implementation in larger carpets and various fluid tasks. Our results show that given identical helices, optimal pumping configurations are influenced by the size of the flow meter. We also show that intuitive designs, such as uniform placement, do not always lead to a high-performance carpet.

Highlights

Bacterial carpets consist of multiple flagellated bacteria naturally or artificially adhered to a surface, with the flagella positioned outward into the fluid
The study of fluid flow or pumping by bacterial carpets has been of significant interest in microfluidics for the past couple of decades
We model a bacterial carpet as a collection of rigid, helical filaments attached to a stationary planar wall and immersed in a viscous fluid

Summary

Introduction

Bacterial carpets consist of multiple flagellated bacteria naturally or artificially adhered to a surface, with the flagella positioned outward into the fluid. There are numerous experimental studies on flow and mixing induced by helices [3,4,5], biomimetic cilia [6,7], and bacterial carpets [1,2,8,9,10]. A number of numerical studies have been performed to examine the effect of these carpets on mixing and pumping [12,13,14,15]. Several of these studies have observed that helical placement and phase shifts alter the qualitative and quantitative characteristics of the fluid flow. To the best of the authors’ knowledge, no existing work has systematically looked at optimizing flow subject to these helical parameters

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Conclusion