Fig. 1.

Illustration of the commonly used bioprinting techniques extrusion (A), inkjet (B), VAT photopolymerization (C), and laser-assisted bioprinting (D). While, according to the ASTM classification for standards in additive manufacturing, the methods of inkjet and laser-assisted bioprinting are grouped together under the term jetting-based bioprinting, for illustrative purposes, both techniques are considered separately here. A Bioink is extruded using pneumatic or mechanical pressure. B Thermal inkjet uses heat-induced bubble that pushes the bioink through the nozzle. Piezoelectric actuator produces acoustic waves that propel the bioink through the nozzle. C Photopolymerization occurs on the bioinks surface, where light-sensitive bioink is exposed to light energy. D Bubble formed by laser pulse propels droplet of bioink. Figure illustration on the basis of Kačarević et al. [13] and Liu et al. [119]