Measuring rheology of bacteria streamers using digital holographic microscopy and microfluidics

Wenjun Yi, Micah Wyssmann, Kok Suen Chen, Jian Sheng

Biofilm consisting of structured bacterial communities protected by extracellular polymer matrix from environmental insults such as antibiotics, biocides, and mechanical abrasions. Although a large amount of research has been conducted on mechanisms of biofilm formation, rheological properties (e.g., viscoelasticity) of a live biofilm are less well understood due to the lack of experimental tools to quantify material properties under realistic flow conditions. In this study, we present an experimental technique that combines a creep-recovery microfluidics platform enabling the in-situ growth of bacteria biofilms and digital holographic microscopy (DHM) to provide strain and flow stress measurement. To demonstrate the methodology, Pseudomonas fluorescens biofilms are formed in-situ in the platform under flow, and isolated micropillars is employed as sites for growth of a single extracellular streamer filament. 3D Flow measurements near streamers by DHM resolves stresses (loads) over deforming streamers (strain) during a creep-recovery test. Effects of load memory on viscoelasticity will be investigated.