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Bioprinting of multimaterials with computer-aided design/computer-aided manufacturing
viscosity and gelling speed, hence reducing the support materials [29,30] . The software involved has
process window to bioprint freeform biological the capability to generate the support structures
structures . Different bioprinting strategies needed for the part and to assign a secondary
[24]
have been used to overcome such material-based material to the supports. Using materials of
limitation for bioprinting freeform constructs . different properties, the supports can be removed
[25]
One such strategy is through the use of support preferentially during post-processing .
[31]
materials that help assist in forming structural In general, the purpose for support structure
integrity for the build materials. in additive manufacturing is to provide structural

2.1 Support structure generation in additive integrity where regions of object display
manufacturing overhanging or floating features. Support structure
generation in additive manufacturing can be
The use of build/support configuration is prevalent distinguished according to the density difference
in 3D printing. 3D printing technologies, such between build and support parts. For instance,
as inkjet printing [26-28] , and material extrusion support structure generation for metal powder bed
such as fused deposition modeling make use of fusion and stereolithography (STL) is designed
multimaterials to differentiate the part from the as struts . Comparatively, support material can
[32]

Table 1. Comparison of the current technology for multimaterial deposition and support structure
generation across additive manufacturing technologies.

Material Form AM technologies Multimaterial Support Function of
deposition structure support structure
generation
Metal Powder Powder bed Selective laser  Struts - Support floating and
fusion [40-43] melting overhanging objects
Electron-beam  - Melt pool heat
melting dissipation
- Prevent thermal
warping prevention
Directed energy LENS  NA
deposition [44]
Polymer Powder Powder bed Selective laser  NA
fusion [45-47] sintering
Powder Binder jetting [45-47] Indirect inkjet  NA
printing (Binder 3DP)
Liquid, Material jetting [45,47] Polyjet/inkjet  Partially - Support floating
photopolymer printing or fully and overhanging
encapsulate objects
build part
Solid, Material Filament deposition  Lattice - Support weight
thermoplastic extrusion [45,47] modeling scaffolding imbalance
structures
Liquid, Bioprinting  Partially - Support floating
hydrogel or fully and overhanging
encapsulate objects
build part - Improve print
fidelity
Liquid, Vat Stereolithography  Struts - Support floating
photopolymer polymerization [45,47] and overhanging
objects
LENS: Laser engineered net shaping
66 International Journal of Bioprinting (2020)–Volume 6, Issue 1