Table 4 Bioprinting: categories, mechanism involved, advantages and disadvantages
From: Three-dimensional in vitro culture models in oncology research
Type | Subtype | Advantages (+)/disadvantages (−) |
|---|---|---|
Droplet-based bioprinting | Inkjet-based bioprinting: either relies on Plateau-Rayleigh instability phenomenon (CIJ), or on the generation of droplets by a thermal, piezoelectric or electrostatic stimulus that overcome the surface tension force of the bioink at the nozzle (DOD) EHDJ: use back pressure to push the bioink to the nozzle tip until forming a spherical meniscus. Then, a high voltage is applied between the tip of the nozzle and the bioink, which creates an electric field that overcomes surface tension Acoustic bioprinting: the bioink is ejected from an open pool instead of a nozzle, thanks to the action of an acoustic field whose waves focalize at the pool exit and overcome the surface tension force of the bioink at the nozzle Microvalve bioprinting: a voltage applied will open the microvalve that gate the nozzle tip, and with association with a pneumatic back pressure, the bioink is ejected | + High printing speed + Low cost + High cell viability − Require specific equipment − Low cell density printable − Low bioink viscosity − Clogging issues − Weak mechanical integrity of the construct |
Extrusion-based bioprinting | Pneumatic: use of air pressure to extrude the bioink Mechanical: use of a piston or a screw to extrude the bioink Solenoid: use the effect of electric current on magnetism. A ring magnet localized around the nozzle attracts a second magnet that floats in the bioink inside the syringe barrel, thus closing the nozzle hole and preventing bioink to flow through. When an electrical pulses are generated into a coil surrounding the syringe barrel, it cancels the magnetic attraction between the ring and floating magnet, allowing the bioink to flow through the nozzle onto the substrate | + Simplicity of the system + High scalability + Good structural integrity + High cell density printable + High bioink viscosity − Lower resolution than inkjet- and laser-assisted bioprinting (100 µm) − High sheer stress can impact cell viability − Clogging issues − Slow printing speed − Require sheer thinning bioink |
Laser-assisted bioprinting | Cells in bioink: consists in a donor slide that contains a transparent layer, most often a laser energy-absorbing layer, and a layer of cell trapped in bioink. A laser goes through the transparent layer, its energy is absorbed by a metal or biopolymer layer, which creates local evaporation and the high gas pressure propels a droplet from the bioink layer onto the substrate (LIFT, AFA-LIFT, BioLP, MAPL-DW) Cells in liquid media: cells are in suspension in liquid media placed above a substrate, and a weak powered laser go through cell suspension and push the cells down onto the substrate (LG DW) | + High cell viability + High resolution (5 µm) + Good printing speed + No clogging issues + Higher cell density printable than with droplet-based bioprinting − Low bioink viscosity − Laser exposure can lead to phototoxic damages − Metallic nanoparticles in the absorbing layer can be cytotoxic − High cost − Complexity of the donor slide production |
Stereolitography bioprinting | Direct laser writing: a laser trace lines across the photopolymer surface to cure it Mask projection: use either a patterned physical or digital mask to filter light and cure a whole layer of photopolymer at once | + Highest resolution among all bioprinting methods + Low cost + High cell density printable + No clogging issues + Good printing speed with masks + High bioink viscosity − UV and IR phototoxicity can lead to low cell viability − Few bioink compatible with stereolithography bioprinting |