Figure 2.

(a) Single stroboscopic image taken at 300 Hz of a live cell (top channel) and an immotile cell (lower channel), both fluorescently labeled, in a microfluidic channel. Despite the channel flow velocity of 1.6 mm/s, which is much higher than their own velocity, live T. brucei (top) are able to swim the width of the channel, whereas a dead cell stays in the same lateral position and is carried by the flow. (b) Montage of a cell moving in pressure-driven flow through a microfluidic channel. The cell (indicated by the black arrow) moves in a sinusoidal trajectory within an upstream orientation. Channel width is 23 μm. In the lowest panel, the cell’s actual trajectory is superimposed to the overlay of all frames in the montage, clearly showing the cell moving toward and away the channel wall.