Figure 2.

Transparent microfluidic chip prototypes were printed using an adapted 3D‐DLP print process. The printed chips offer a wide opening for the print head over the central chamber (A) that is closed with a plug after the bioprinting process (B,C). After testing different chip geometries, the final design contains a 3 mm wide tissue chamber with two round pillars separating the chamber from the channels (D). The COP custom‐fabricated chips offer three OOC units on a standard microscopy slide format accessible via Luer connectors. The bottom of the chip is covered by a double‐sided cytocompatible tape, which is sealed by a protective foil (E). After the bioprint process, the protective foil is removed and the chip is sealed with a polymer coverslip (F). The surface energy (G) and contact angle to a bioprinted agarose hydrogel (H) show no significant (ns) difference between both substrate materials, though the roughness is smaller for the DLP‐printed surface with *** for p < 0.001 (I).