Effects of applied pressure on bacterial transport through confined spaces

In this study, we investigated the ability of bacterial cells to pass through pores smaller than their own size. This information is critically important for both high-tech membrane filters used in sterilization processes and low-cost removal of bacteria from drinking water, such as riverbank filtration process. For this purpose, we designed and fabricated hybrid glass polymer microfluidic devices containing 950-nm-tall constrictions with varying widths and lengths. Initially, 1-μm-diameter beads were used as a control to study the effect of pressure on rigid objects collecting at constrictions and passing through them. Bacterial studies were done with Escherichia coli to examine the cellular behavior in these micro confinements. The results showed that both beads and cells could be pushed through the constrictions by applying external pressure to the fluid. Bacterial cells required less pressure than similarly sized beads to enter the constrictions, as they deformed their shape while moving through the constriction.