Table 1. A Comparison of Bioprinting Techniques Based on Resolution, Rheological Requirements, and Key Advantages and Disadvantages.

printing platform	maximum resolution	bioink viscosity	key advantage	key limitation	ref
pneumatic/piston extrusion	∼200 μm	30–600 × 106 mPa·s	printing high viscosity, cell-laden materials with high cell density	high shear forces required to print can compromise cell viability
cross-linking during extrusion	∼100 μm	30–600 × 106mPa·s	printing low viscosity polymers with high fidelity	delamination of printed layers due to rapid cross-linking	(44)
co-extrusion	∼20 μm	12–600 × 106mPa·s	allows for the generation of structures with mechanical and biological heterogeneity	requires multiple print heads capable of extruding materials under different conditions	(64,141)
suspended extrusion	∼20 μm	5–800 mPa·s	high-resolution printing of low viscosity polymers with control over flow postprinting	precise mechanisms behind flow prevention still poorly understood	(70,71,75)
piezoelectric jetting	∼45 μm	3.5–30 mPa·s	high resolution and high printing speed allow for rapid cell patterning	piezoelectric pulses have been shown to negatively affect cell viability	(28,91,93)
thermal jetting	∼45 μm	3.5–30 mPa·s	thermal ejection process is far more favorable for cell viability than piezoelectric jetting	narrow range of bioink viscosities can be used when compared to extrusion-based systems	(28,91,93)
microvalve-based jetting	∼220 μm	1–70 mPa·s	increased viscosity range for bioinks	high shear stress can compromise cell viability	(104,142,143)
acoustic jetting	∼60 μm	1–150 mPa·s	wide range of bioink viscosities can be used due to the system being nozzle-free	disturbancies can easily affect droplet ejection	(110,112)
vector-wise SLA	∼1 μm	<5 Pa·s	high speed and high-resolution generation of structures	difficult to combine multiple materials	(140)
mask irradiation	∼1 μm	<5 Pa·s	ability to reticulate multiple areas of a resin in a single laser pulse	difficult to combine multiple materials	(130)
two-photon polymerization	100 nm	<5 Pa·s	highest resolution form of bioprinting commercially available	optically transparent materials are needed	(144)
laser-assisted bioprinting	∼20 μm	1–300 mPa·s	high resolution generation of structures from bioinks in solid or liquid phase	laser pulses can impact viability with >15% cell death	(44,139)