Evaluation of bioink printability for bioprinting applications

Abstract

Three-dimensional (3D) bioprinting, as a freeform biomedical manufacturing approach, has been increasingly adopted for the fabrication of constructs analogous to living tissues. Generally, materials printed during 3D bioprinting are referred as bioinks, which may include living cells, extracellular matrix materials, cell media, and/or other additives. For 3D bioprinting to be an enabling tissue engineering approach, the bioink printability is a critical requirement as tissue constructs must be able to be printed and reproduce the complex micro-architecture of native tissues in vitro in sufficient resolution. The bioink printability is generally characterized in terms of the controllable formation of well-defined droplets/jets/filaments and/or the morphology and shape fidelity of deposited building blocks. This review presents a comprehensive overview of the studies of bioink printability during representative 3D bioprinting processes, including inkjet printing, laser printing, and micro-extrusion, with a focus on the understanding of the underlying physics during the formation of bioink-based features. A detailed discussion is conducted based on the typical time scales and dimensionless quantities for printability evaluation during bioprinting. For inkjet printing, the Z (the inverse of the Ohnesorge number), Weber, and capillary numbers have been employed for the construction of phase diagrams during the printing of Newtonian fluids, while the Weissenberg and Deborah numbers have been utilized during the printing of non-Newtonian bioinks. During laser printing of Newtonian solutions, the jettability can be characterized using the inverse of the Ohnesorge number, while Ohnesorge, elasto-capillary, and Weber numbers have been utilized to construct phase diagrams for typical non-Newtonian bioinks. For micro-extrusion, seven filament types have been identified including three types of well-defined filaments and four types of irregular filaments. During micro-extrusion, the Oldroyd number has been used to characterize the dimensions of the yielded areas of Herschel-Bulkley fluids. Non-ideal jetting behaviors are common during the droplet-based inkjet and laser printing processes due to the local nonuniformity and nonhomogeneity of cell-laden bioinks.

Nucleotide lipid-based hydrogel as a new biomaterial ink for biofabrication

“…The successful printability of diC 16 dT-DMEM@+ BmI was related to its rheological properties 18,47 , including shear thinning capacity and thixotropic properties, as previously highlighted. Printed lattices maintained their shape during the printing step and furthermore showed some flexibility (Fig.…”

Printability of Methacrylated Gelatin upon Inclusion of a Chloride Salt and Hydroxyapatite Nano‐Particles

“…The collapse of the extruded lines and apparent increase in line width from that expected (based on needle diameter) is the result of the ease with which the ink may spread (or flow) following extrusion on to the print bed due to the force of gravity. While the single‐layer prinability ratio is an acceptable initial screening approach for comparing inks (under one set of printing conditions), future studies will need to consider building more rigorous phase diagrams for the chosen ink(s).…”

Bioprintability: Physiomechanical and Biological Requirements of Materials for 3D Bioprinting Processes

“…Due to their low fabrication temperature (~37 °C or lower), only a limited subset of polymer materials can be used as bioinks for 3D printing processes since they need to satisfy several important criteria for printability. These include: (i) rheological properties, i.e., the ability of the material to deform, flow, and be precisely controlled to form a 3D shape [ 96 ]; (ii) viscosity [ 97 ]; and (iii) surface tension [ 98 ]. These properties are strongly dependent on the printing techniques.…”