Assessing bioink shape fidelity to aid material development in 3D bioprinting

Abstract

During extrusion-based bioprinting, the deposited bioink filaments are subjected to deformations, such as collapse of overhanging filaments, which compromises the ability to stack several layers of bioink, and fusion between adjacent filaments, which compromises the resolution and maintenance of a desired pore structure. When developing new bioinks, approaches to assess their shape fidelity after printing would be beneficial to evaluate the degree of deformation of the deposited filament and to estimate how similar the final printed construct would be to the design. However, shape fidelity has been prevalently assessed qualitatively through visual inspection after printing, hampering the direct comparison of the printability of different bioinks. In this technical note, we propose a quantitative evaluation for shape fidelity of bioinks based on testing the filament collapse on overhanging structures and the filament fusion of parallel printed strands. Both tests were applied on a hydrogel platform based on poloxamer 407 and poly(ethylene glycol) blends, providing a library of hydrogels with different yield stresses. The presented approach is an easy way to assess bioink shape fidelity, applicable to any filament-based bioprinting system and able to quantitatively evaluate this aspect of printability, based on the degree of deformation of the printed filament. In addition, we built a simple theoretical model that relates filament collapse with bioink yield stress. The results of both shape fidelity tests underline the role of yield stress as one of the parameters influencing the printability of a bioink. The presented quantitative evaluation will allow for reproducible comparisons between different bioink platforms.

3D Bioprinting of Architected Hydrogels from Entangled Microstrands

“…3, A and B). To identify the yield stress necessary to induce flow different methods can be employed ( 21, 22 ). In this study we used the crossover of G’ and G’’ to identify the flow point.…”

How to Formulate for Structure and Texture via Medium of Additive Manufacturing-A Review

“…It is prevalent to further classify the materials into natively printable (i.e., confectionery, dairy, hydrogels) versus non-natively printable (i.e., plants, meat) [31,34]. However, this cannot be accurate for several reasons: (i) there is no consensus on how to assess or predict shape fidelity, let alone printability [74]. (ii) Printability is affected by multiple factors (temperature, components and additives) [75].…”

Void‐Free 3D Bioprinting for In Situ Endothelialization and Microfluidic Perfusion

“…An alternative strategy, aimed at building more complex networks, is to directly print structures with interconnected void spaces (pores or channels) . However, the presence of voids regularly results in structural instability during printing, whereby the top layers cause the lower layers to buckle and deform the underlying pores . This factor has led to the development of alternative print‐casting methodologies, in which a vascular template is 3D printed using fugitive inks, such as carbohydrate glass or Pluronic F‐127 .…”