Figure 2.

Schematic diagram of (a) thermal inkjet printers electrically heating the printhead to produce air-pressure pulses that force droplets from the nozzle, whereas acoustic printers using pulses formed by ultrasound pressure from piezoelectric element; (b) microextrusion printers using pneumatic or mechanical (piston or screw) dispensing systems to extrude bioink beads; and (c) laser-assisted printers utilizing focused laser beams on an absorbing substrate to propel bioink onto a collector substrate, courtesy of [24].