Nanostructured Complex Fluids for Biofilm Removal

Effective methods for cleaning surfaces are of increasing importance in the healthcare sector. Medical instruments such as endoscopes and various tubes for dental and medical procedures are continuously susceptible to cross-contamination and biofilm formation as these devices are typically reused from patient to patient. Complex fluids such as micro-fibrillated cellulose are particularly useful in this application of cleaning as its heterogeneous structure has been shown in our experiments to be effective in removing both adhered particles and bacteria from surfaces. The goal of this study is to understand the role of the normal and wall shear stresses on cleaning and how altering parameters such as strain rate and cellulose fiber concentration affects the cleaning process. The main component of our experimental model is a rectangular microchannel made of PDMS and a glass slide, where we can control the flow rate, and hence the wall shear rate, for different choices of fluids, whose rheology we measure. In particular, we culture bacterial (Staphylococcus aureus) biofilms on the glass side of a channel and, using fluorescent microscopy, observe biofilm removal by the flow. Finally, we characterize the flow field and cleaning as a function of time with the use of particle image velocimetry (PIV) and other image analytical techniques.