Fig. 2.

Fabrication of a microvascular network by photolithography. A Photolithographic approach to generate cellular micropatterns. a Crosslinked chitosan pattern after 180 s of UV exposure. Bar = 100 μm. b, c Engineered tubular structures of BCAEC and HUVEC scanned by confocal laser-scanning microscopy (CLSM). 3D images showed a lumen within the tubular structures. Bar = 20 μm. (Figure reprinted with permission from Ref. [32]). B, a–c SEM image of the backside lithography technique at different magnifications. We can observe the gradation in height according to the width of the channels. (Figure reprinted with permission from Ref. [36]). C Culture of primary human lung microvascular endothelial cells (HLMECs) in the hourglass-shaped channels. Scale bar, 50 µm. (Figure reprinted with permission from Ref. [37])