The Measurement And Application Of Fluid Flow Generated By Confined Bacteria

In many technological applications,materials are transported by fluid flow at micro/nanometer scales.Conventionally,macroscopic apparatuses,such as syringe pumps,are used to drive the flow.But pumps are bulky and not ideal for miniaturization.Our work explores the possibility of utilizing motile bacteria which have already adapted to microscopic environment as microscopic pumps.Previous research have shown that immobilized bacteria could generated flow which could be used to transport cargo.But their methods of blotting or flow deposition have limit in precisely controlling the flow.We successfully solve this problem by using prescribed configurations fabricated by a Two-Photo fabrication system.We used a photosensitive resin and a pulsed laser to fabricate structures with cavities of bacterial size on a cover glass.When a bacterium swim into a cavity,it will be stuck with its flagella keeping rotate.The rotating flagella outside the cavities generate the fluid flow around.The flow generated could move silica particles with 2 ?m in diameter across a distance of 60 ?m in 15 seconds.In addition,we designed complex structures to demonstrate the robust of this flow.Silicon particles could be transported through a spiral or a square-shaped channel when bacteria are confined along the edges.Concentration of particles can be achieved by arranging the direction of several linear structures,producing directional flow to a central area.In our experiment,the flow speed generated is about 25 ?m/s which is limited only by the swimming capability of the E.coli.By using bacteria with a faster swimming speed,it would be possible to generate a faster flow.We believe that our approach will be useful both for generating new bio-hybrid devices and for studying fundamental interactions between multiple bacteria.