Study of Viscosity Behavior and Surface Properties of the Active System by Escherichia coli/Water/Polyvinylpyrrolidone

The study of the behavior of active suspended fluid introduced a new topic for a wide range of applications such as reactors, microfluidic pumps, cultivating surfaces and antibacterial surfaces. The motility of bacterial suspension has generated a shear force (Hydrodynamic interaction) across the cells, which has an effect on the fluid viscosity. In this study, shear rheometer was used to evaluate the viscosity behavior of Escherichia coli (E. coli) in a water/polymer environment as a function of bacteria concentration and shear rate.

In the experimental study, the activity of E. coli was evaluated by choosing the constant concentration (0.01g/ml) and molecular weight of polyvinylpyrrolidone (360KDa). Also, the surface tensions of E. coli, Acetobacter xylinum, and S. aureus solutions were calculated using Wilhelmy test.

Activity of E. coli suspension results the lower viscosity comparing with the bacteria-free solution. The relative viscosities of the solutions were analyzed in a wide range of shear rates and bacterial concentrations. At a low shear rate up to1S-1, the relative viscosity was found to be less than a unit value (Less than water). Also, due to the collective motility break up to smaller parts at high shear rates, the viscosity increased. The critical volume fraction was defined in determined bacterial concentration (0.8v/v) to analyze the collective movement of bacteria. The interfacial tension was reduced by bacteria presence of three different stain types that confirmed the effect of bacteria activity on the flow behavior.

The activity of E. coli bacteria makes it easy for fluid to flow at low shear rates. The viscosity reduction of active particle has a potential to demonstrate a variety of novel applications when a reduced energy level is needed.