Table 1.
3D printing techniques for bone implants fabrication.
| 3D printing techniques | Process | Materials | Advantages | Drawbacks |
|---|---|---|---|---|
| 3D plotting/direct ink writing | The extrusion of injectable inks based on the predesigned shapes and structures | ● PCL[28] ● PCL/HA[29] ● CaP cement[30] ● Alginate[31] ● Alginate/Nano HA[32] ● Collagen[33] ● Bioceramic[34] ● Chitosan[35] ● Bioactive glass/alginate[36] |
● Mild conditions benefit the loading of biomolecules and cells | ● A sintering process is needed for some materials ● Low fabrication accuracy |
| Stereolithography (SLA) | After exposure to focused light based on predesigned structure, polymer solidifies at focal points while polymer without exposure remains liquid. | ● PTMC/nano HA[37] ● PPF [38] ● PEG[39] ● HA/BCP/polyfunctional acrylic resins[40] ● Bioactive glass/rigid resin/1,6-hexanediol diacrylate[41] |
● Mild conditions benefit the loading of biomolecules and cells ● High fabrication accuracy ● Can obtain complex internal structures |
● Photopolymer is needed ● Defective biodegradation rates and biocompatibility |
| Selective laser sintering (SLS) | A high-powered laser is used to sinter powder, thereby binding the material together to create a solid structure | ● PCL[42] ● CaP/PHBV[43] ● PCL/HA[44] ● Bioactive glass[45] ● PVA[46] |
● Needs no support structures ● Fast |
● Elevated temperatures ● The resolution depends on the diameter of the laser beam |
| Selective laser melting (SLM) | A high-powered laser is used to melt metal powder, then the scaffolds with the desired structure could be obtained after cooling | ● Pure titanium[47] ● Magnesium[48] ● TiAl6V4[49] |
● Large range of metals available | ● Elevated temperatures ● The resolution depends on the diameter of the laser beam |
| Fused deposition modeling (FDM) | The extrusion of heated polymer or ceramic with heated polymer binder and hardening post-printing to form a solid construct | ● CaP/PLA[50] ● PCL/HA[51] ● PVA/β-TCP[52] ● PLA[53] ● PLA/HA[54] |
● Needs no support structure | ● Elevated temperatures ● Low fabrication accuracy |
| Powder printing | Jetting liquid binders onto powder bed to form each layer of desired construct. After fresh powders added, the process repeated layer by layer. | ● BCP/phosphoric acid[55] ● TCP/alginate/phosphoric acid[56] ● CaP/collagen/phosphoric acid[57] |
● Large range of materials available | ● Low fabrication accuracy ● Post-treatments (for example depowdering and sintering) are needed |
| Inkjet based bioprinting | The ejection of bioinks from print head nozzle onto substrates with thermal or piezoelectric forces | ● PEGDMA[58] ● PEGDMA/GelMA[59] |
● Inexpensive ● Compatible with low-viscosity biomaterials |
● Low fabrication accuracy ● Reduction of cell viability because of the eject force |
| Extrusion-based bioprinting | After extruded under computer control, bioinks composed of cells and biomolecules were crosslinked to form desired structures | ● PEG[60] ● Alginate[61] ● Alginate/PVA/HA[62] ● Gelatin/Alginate[63] ● GelMA[64] |
● Mild conditions benefit the loading of biomolecules and cells | ● Low mechanical properties ● Low fabrication accuracy ● Restriction of materials |
PCL: poly(ε-caprolactone), HA: hydroxyapatite, CaP: calcium phosphate, PTMC: Poly(trimethylene carbonate), PPF: Poly(propylene fumarate), PEG: polyethylene glycol, BCP: biphasic calcium phosphate, PVA: polyvinyl alcohol, PLA: polylactic acid, β-TCP: β-tricalcium phosphate, PEGDMA: poly(ethylene) glycol methacrylate, GelMA: gelatin methacrylate