FIG. 1.

Microstructures with funnel walls. (A) Schematic drawing of the interaction of bacteria with the funnel opening. Bacteria on the left side may (trace 1) or may not (trace 2) get through the gap, depending on the angle of attack. On the right, all bacteria colliding with the wall are diverted away from the gap (traces 3 and 4). (B) Scanning electron micrograph of the device. (C) Distribution of incoming and outgoing angles for bacteria colliding with a wall. Data were taken for 70 events.