CARTILAGE 3D PRINTING - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 261

FIGURE 12.3
Overview of the mechanisms of action for each 3D printing method: (a) stereolithography traps cells that are
suspended in a liquid photosensitive monomer hydrogel, dark gray represents the focused laser-induced cross-
linked solid hydrogel; (b) extrusion pushes suspended cells from a column through a contacting nozzle; (c) thermal
ink-jet uses a pressure increase formed by a vapor bubble to force the mix of cells and ink from a nozzle; (d) laser
induced forward transfer (LIFT) vaporizes a sacrificial layer of cells suspended on a polymer to push cells toward
the substrate.
All techniques share a key characteristic: the reliance on some form of bioink. This can take many
forms; in the simplest case, it is a biocompatible, printable fluid. In most cases, the bioink is intended as a
carrier for cells, not just a tissue engineering scaffold material. In these instances, the fluid must provide
both structure for the 3D object and a favorable environment for cell viability. A major component of many
bioinks is a hydrogel, often agarose or HA ( Billiet et al., 2012; Jabbari, 2011; Schuurman et al . , 2013a ).