Fig. 3.

Major classification of tissue engineering-targeted 3D bioprinting technology. Briefly, a standardized micro-construction as designed by the digital cubic prototype can be achieved either in use of gravity hanging drops controlled by an inkjet-based 3D bioprinter (A), by facilitating mechanical squeezing forces through the regulation of an extrusion-based 3D bioprinter (B), or through the direct-writing function of a laser-guided, stereolithography, or digital light processing 3D bioprinter (C). The above three printing strategies can be used either individually or in combination according to the specific needs of tissue engineering, the purpose of which is to achieve a closer simulation of native tissues and organs.