Figure 3.

Bioprinting is usually accomplished using a combination of gel and cells. Laser assisted bioprinting (A) using Laser-induced forward transfer (LIFT) relies on the focused energy of a laser onto an energy absorbing ribbon to induce bioink droplet formation. This technique is advantageous because it avoids the problem of clogging of the bioink nozzle that plagues other bioprinting techniques. Multiphoton excitation-based printing (B), is accomplished via photocrosslinking of proteins or polymers in the focal volume of the laser and excels in its high resolution and ability to polymerize many native proteins that do not form hydrogels spontaneously outside the body. Inkjet printing (C), one of the most common printing techniques, relies upon a vapor bubble or a piezoelectric actuator to displace material to extrude the bioink from a nozzle. Robotic dispensing (D) employs other mechanical means of displacing bioink under robotic control.