Fig. 3.

Some FF circuits carrying out different functions. Colored dyes were pipetted manually into input drops, and they are flowing (colored arrows) to sink drops autonomously. Insets illustrate how accurately pinning lines are built. a Mixing 8 fluids. b Generating a stable concentration gradient across two laminar streams after the junction (side view below). c Flow focusing the central laminar stream after the junction (side view below). d Generating a flow-free diffusion gradient across the central conduit (inset). e Feeding circuit after 90 s (upper) and at equilibrium (lower); dyes were pipetted into large drops on the left, which then feed the small chambers