Figure 11.

Recent strategies in multi-material extrusion and stereolithographic bioprinting. (A) Schematic of a multi-material extrusion bioprinter consisted of seven bioink outlets and a single nozzle. (B, C) Photographs of bioprinted structures with (B) cubical structures, circular structures, pyramid and stripes as well as (C) different organ designs. (D) Bioprinted GelMA-hydroxyapatite structures to display a gradient of osteogenic induction properties. (E) Bioprinted circuit structure using different concentrations of CNTs in GelMA to create different resistance in the circuit (displayed by green LED intensity). Reproduced with permission from ref.^[174]. (F) Planar schematics showing the setup of multi-material stereolithography, including a UV lamp (385 nm), optical lenses and objectives, a DMD chip, and a microfluidic device. (G) Photographs showing the bioink exchange processes in the microfluidic chip for a star pattern and two rectangular patterns. (H) A tumor angiogenesis model with (left) schematic, (middle) mask for bioprinting, and (right) the bioprinted GelMA vascularized construct perfused with food dye. (I) A skeletal muscle model with (left) schematic, (middle) mask for bioprinting, and (right) fluorescence micrograph of the bioprinted GelMA construct containing patterned C2C12 cells (red) and fibroblasts (blue). (J) A tendon-to-bone insertion model with (left) schematic, (middle) mask for bioprinting, and (right) bright-field optical image showing the bioprinted dye-laden GelMA construct containing the corresponding features. Reproduced with permission from ref.^[180].