Figure 1.

Schematic showing the printing approach to fabricate 3D channels embedded within hydrogel matrix: (a) sequential printing of photocurable matrix hydrogels with groove structure and a sacrificial ink within printed matrix layer-by-layer; (b) an enlarged image of a single layer, notably, because the diameter of extrusion nozzle and piezoelectric nozzle is different, a hydrogel layer requires two or three layers of sacrificial ink to match the thickness; (c) post-printing process including full curing, immersing in a CaCl₂ solution to crosslink and remove sacrificial ink to fabricate channels.