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Biofabrication holds great potential in the fields of regenerative medicine and physiological 3D in vitro models by allowing the manufacture of complex tissue constructs with a higher degree of biomimicry to native tissues than do current biomedical solutions. As the number of biofabrication technologies being developed continues to expand, it is of paramount importance to adopt a concerted terminology framework and avoid generalizations. The ratio between the spatial resolution and the timescale of manufacture could be considered as a reliable measure to aid in the selection of an appropriate biofabrication technology for a desired application. Biofabrication holds the potential to generate constructs that more closely recapitulate the complexity and heterogeneity of tissues and organs than do currently available regenerative medicine therapies. Such constructs can be applied for tissue regeneration or as in vitro 3D models. Biofabrication is maturing and growing, and scientists with different backgrounds are joining this field, underscoring the need for unity regarding the use of terminology. We therefore believe that there is a compelling need to clarify the relationship between the different concepts, technologies, and descriptions of biofabrication that are often used interchangeably or inconsistently in the current literature. Our objective is to provide a guide to the terminology for different technologies in the field which may serve as a reference for the biofabrication community. Biofabrication holds the potential to generate constructs that more closely recapitulate the complexity and heterogeneity of tissues and organs than do currently available regenerative medicine therapies. Such constructs can be applied for tissue regeneration or as in vitro 3D models. Biofabrication is maturing and growing, and scientists with different backgrounds are joining this field, underscoring the need for unity regarding the use of terminology. We therefore believe that there is a compelling need to clarify the relationship between the different concepts, technologies, and descriptions of biofabrication that are often used interchangeably or inconsistently in the current literature. Our objective is to provide a guide to the terminology for different technologies in the field which may serve as a reference for the biofabrication community. the fabrication of hierarchical constructs with a prescribed 2D or 3D organization through automated assembly of preformed cell-containing fabrication units generated via cell-driven self-organization or through preparation of hybrid cell–material building blocks, typically by applying enabling technologies, including microfabricated molds or microfluidics. biological constructs engineered by using in a predefined manner cells, biomaterials, and/or biological factors alone or in combination with each other. formulation of material(s) and biological molecules or cells processed using bioprinting technologies. a material that is used as (part of) a medical device or an advanced therapy medicinal product to replace, restore, or regenerate a tissue or organ and its function. the use of computer-aided transfer processes for patterning and assembly of living and non-living materials with a prescribed 2D or 3D organization to produce bio-engineered structures serving in regenerative medicine, pharmacokinetics, and basic cell biology studies. In this context, additive manufacturing of 3D scaffolds able to instruct or induce the cells to develop into a tissue mimetic or tissue analog structure, for example, through distinctive cell interaction, hierarchical induction of differentiation, or functional evolution of the manufactured scaffolds falls within bioprinting. a cluster of cells with a spherical shape, typically formed by allowing a cell suspension to settle into a droplet of media. a material processing technology that uses high electrical voltage to fabricate fine fibers from polymer solution or molten polymer. Fibers are deposited onto a collector, with a random or defined alignment. the rate of fabrication of a scaffold or of a bioprinted construct using biofabrication technology. In the RTM ratio it can be calculated as the time to fabricate a 10−6 m3 (1 cm3) cube, lying on one of its faces. additive manufacturing technologies that can be used for bioprinting in which a thermoplastic material, in shape of filament or pellet, is hot-extruded and deposited to form a layer of solid material. Using a layer-by-layer approach a 3D scaffold or a 3D construct is built. a biofabrication approach that uses an additive manufactured mold in which a bioink is cast, injected, or compressed. printing systems able to bioprint constructs in a layer-by-layer manner by ejecting bioinks in the form of droplets via the nozzle head. Droplet ejection is controlled either by piezo- or thermal actuators (ink-jet), or by solenoid microvalves (valve-jet). also known as laser-induced forward transfer (LIFT), a bioprinting technique that uses laser pulses to deposit a bioink from a donor slide onto a substrate. a technology based on geometrically constrained minute volume transport in micro-channels. This technology can also be used to fabricate strands of hydrogels that are suitable as building blocks for successive assembling processes. biofabrication approach in which microunits of cell-laden hydrogels are used as regenerative building blocks. the smallest detail that can be fabricated using a biofabrication technology. bioprinting technologies that dispense continuous filaments of hydrogel materials that are extruded through nozzles using a piston, a screwing system, or pneumatic pressure as the driving force. additive manufacturing technologies that can be used for bioprinting based on the extrusion of polymers dissolved in volatile solvents. The quick evaporation of the solvent allows shape retention of the 2D pattern deposited by the 3D micropositioner. With a layer-by-layer approach a 3D scaffold can be fabricated. an additive manufacturing technology that can be used for bioprinting in which a jet of binder is directed at a powder-bed to define a pattern. The solvent binds to the powder, forming a slice of solid material; subsequently a new layer of powder is laid down, and the process is repeated to build the scaffold layer-by-layer. a measure used to rank the performance of biofabrication technologies. The RTM ratio is defined as the ratio of the spatial resolution to the time required for biofabricating a bio-engineered structure; a larger RTM ratio represents a more efficient process. an additive manufacturing technology that can be used for bioprinting in which a solid material is ablated using a very short time-duration laser pulse. If the ablation process is conducted in all the three directions, or if laminated porous films are stacked and bonded on top of each other, a 3D structure can be created. an additive manufacturing technology that can be used for bioprinting in which a beam of laser light is selectively directed to a powder-bed, generating local heat and forming patterns of fused material; after its solidification, a new layer of powder is laid down and the process is repeated to build the scaffold layer-by-layer. an additive manufacturing technology that can be used for bioprinting in which light is used to cure a photosensitive resin. Through different irradiation approaches the various stereolithographic systems use a layer-by-layer approach: the energy delivered by the light is sufficient to solidify a particular thickness of the exposed resin and join this layer with the previous one. the notion, introduced by Malcolm Steinberg, that tissues or multicellular aggregates composed of motile and adhesive cells have properties analogous to liquids, evidenced by the fact that irregular tissue fragments spontaneously round up into spheroids, and two fragments composed of different cell types mutually envelope each other. Such tissues can be quantified in terms of apparent tissue surface tension. a laser-based technique that uses a near-infrared ultrashort-pulsed laser to excite in a precise way and to confine space molecules (photoinitiators) to a two-photon state, triggering the polymerization of monomers in solution. This was the first technique that allowed the manufacturing of true 3D nano/micro-structures without supports.
Moroni et al. (Sat,) studied this question.