Cell viability testing using LIVE/DEAD assay on trapped HeLa cells. (a) Initial distribution of HeLa cells after 45 minutes in an optically patterned hydrogel. The starting cell density was approximately 1 × 106 cells/mL in solution. (b-c) Fluorescent images of the same cells from (a), demonstrating approximately 81% viability. Live cells fluoresce green (b), while dead cells fluoresce red (c). Fluorescent cells appear as bright spots in these images.