Fig. 1. Workflow for creating linear 3D cultures.

PDMS device with slit is cut out from a 100 μm high PDMS film and plated on cell culture substrate. An identical device is stacked on top of the base device. Dense cell suspension is then seeded at the edge of the slit. Cell suspension will not go in slit due to surface tension. A nudge with a fine forceps tip breaks surface tension and then slit’s capillary force pulls the cell suspension in. In total, 2 μl cell suspension is again seeded at the previous spot to ensure complete filling of the slit. The device is then incubated for 10 min and sacrificial PDMS layer is removed. After another 5 min of incubation, the whole device is submerged with culture medium and maintained for up to 18 days as described in “Methods”.