Figure 7.

Manufacture of hollow channels using coaxial extrusion. (A): Principle of hollow strand formation. CaCl₂ in gelatin (inner material, yellow) crosslinks the sheath-based gelatin (outer material, orange) causing a stable strand. (B): Strand formation using a coaxial extruder. (C): Visualization of coaxially printed strand hollowness after aspiration of core-based gelatin. (C1): Before addition of dye. (C2): After addition of dye. (D): CLSM micrographs showing a view through the coaxially printed strand (D1): View though the hollow strand with coaxially located HepG2 cells. Visualization of the cells is achieved using live–dead staining. Green: live cells; red: dead cells. (D2) Visualization of the hollow strand using reflection microscopy using a wavelength of 405 nm (scale bar: 200 µm).