Figure 1

Experimental setup. (a) Time-averaged image of the microchannel ($W=600\mu \mathrm{m}$) for $Q=10\mathrm{nl}/\sec$ in each branch and volume fraction $\varphi =0.35\%$. Bacteria are visualized using a white light microscope. The red and blue frames indicate the measurement areas. (b) Concentration profile $C(y)$ normalized by the maximum concentration $C_M$ (black line) and error function fit used to determine the interface position (red line).Reuse & Permissions

Figure 2

Rheology curves. (a) Relative viscosity versus maximum shear rate for motile and nonmotile bacteria at $\varphi =0.8\%$. Inset: Three averaged pictures of the bilaminar flow for flow rates of $Q=0.5\mathrm{nl}/\mathrm{s}$, $Q=2\mathrm{nl}/\mathrm{s}$, and $Q=10\mathrm{nl}/\mathrm{s}$, respectively, for a $\varphi =0.35\%$ bacteria suspension. These images are averaged over 120 images at 22im/s and observed with a $2.5\times$ magnification using phase contrast. The dotted line represents the center position in the channel width. The scale bar corresponds to $200\mu \mathrm{m}$. (b) ${\eta }_r$ versus ${\dot{\gamma }}_M$ at several volume fractions (c) ${\eta }_r$ versus $\varphi$ at several shear rates. The errors bars are estimated using the detection error of the interface position.Reuse & Permissions

Figure 3

Bulk profile measurements for a volume fraction $\varphi =0.75\%$ and shear rates ${\dot{\gamma }}_M=1$, 2, $20{\mathrm{s}}^{-1}$. (a) Bacteria density profile $n(z)$. The horizontal dashed line represents the mean density: $\overline{n}=7.5\times {10}^{12}\mathrm{bact}/\mathrm{l}$. (b) Velocity profile of passive tracers $V_x(z)$.Reuse & Permissions