Fig. 1.

The traveling escape band in a microfluidic channel with opposing gradients. (A) Schematic diagram of the microfluidic device (15). Reservoir 1 (green) contains 2 mM MeAsp. Reservoir 2 (red) contains $20\%$ TB and bacteria. (A, Left) Images of cell density in the channel at different times show the formation of the escape band traveling toward reservoir 2. (A, Right) The cell-density profiles along the length of the channel (x axis) at different times. The cell-density profile is characterized by its peak $h$, width $w$, and peak location $x_p$. (B) The kymograph showing the spatiotemporal dynamics of the cell-density profile. The initial wave approaching reservoir 1 and the escape band formed later are highlighted by the yellow and white arrows, respectively. (C) The rescaled escape-band profiles at different times collapse onto a single curve. C, Inset shows the dependence of peak width $w\left(t\right)$ and the height $h\left(t\right)$ on time (t).