Movie S4.

Delivering liquid to a grid by scanning along a serpentine path (the movie runs in real time, it is truncated after delivering to 3 rows, and frames from it are reproduced in Fig. 3E). A 32 x 32 grid (initially with ∼40 nl per 1 x 1 mm chamber) was made in a 6 cm dish using medium. The movie begins as a hollow stainless-steel dispensing needle with a Teflon sleeve at its tip dispenses blue dye as it scans along a serpentine path delivering ∼70 nl to each of 1,024 chambers in 90 s (some dye is added to the left and right of the grid).