Fig. 1: Porous media flows trap upstream swimming magnetotactic bacteria in vortical trajectories.
From: Fluidic bacterial diodes rectify magnetotactic cell motility in porous environments
a Schematic of the experimental set up. Helmoltz coils generate a uniform magnetic field (blue arrows) to direct magnetotactic bacteria (MC-1) upstream against a pressure-driven microfluidic flow (red arrows). b Schematic of the torques acting on the magnetotactic bacteria. Hydrodynamic torque (orange) due to the local velocity gradient (red) opposes a magnetic torque (blue) due to misalignment of the cell swimming orientation (purple) relative to the magnetic field (light blue). c Measured flow field inside of a corrugated microfluidic channel (wp/wt = 5; Supplementary Fig. 2). Colormap indicates normalized flow speed and markers indicate the location of maximum (Umax; purple) and minimum (Umin; green) centerline flow speed. d−f Experimentally measured cell trajectories (147, 103, and 145 tracks) in a corrugated channel (wp/wt = 5; see also Supplementary Movies 1−3) corresponding to maximal flow speeds Umax = 30, 260, and 350 μm/s. Gray arrows indicate the direction of bacterial transport. Scale bar, 40 μm. g−i Langevin simulations (50 tracks each) corresponding to conditions in (d−f), respectively. Scale bar, 40 μm.
