Computational Modeling and Experimental Characterization of Extrusion Printing into Suspension Baths

Abstract

The extrusion printing of inks into suspension baths is an exciting tool, as it allows the printing of diverse and soft hydrogel inks into 3D space without the need for layer-by-layer fabrication. However, this printing process is complex and there have been limited studies to experimentally and computationally characterize the process. In this work, hydrogel inks (i.e., gelatin methacrylamide (GelMA)), suspension baths (i.e., agarose, Carbopol), and the printing process are examined via rheological, computational, and experimental analyses. Rheological data on various hydrogel inks and suspension baths is utilized to develop computational printing simulations based on Carreau constitutive viscosity models of the printing of inks within suspension baths. These results are then compared to experimental outcomes using custom print designs where features such as needle translation speed, defined in this work as print speed, are varied and printed filament resolution is quantified. Results are then used to identify print parameters for the printing of a GelMA ink into a unique guest-host hyaluronic acid suspension bath. This work emphasizes the importance of key rheological properties and print parameters for suspension bath printing and provides a computational model and experimental tools that can be used to inform the selection of print settings.

Embedded 3D Printing in Self‐Healing Annealable Composites for Precise Patterning of Functionally Mature Human Neural Constructs

“…[11] For highfidelity printing, solid-to-liquid transitions need to be smooth, spatially localized, rapid, and reversible. [12,13,14] Pioneering studies have demonstrated that jammed microgel assemblies (i.e., granular gels) fulfill these requirements and exhibit excellent rheological properties as supports for embedded printing of delicate structures from soft hydrogels and cells. [15,16] Since then, embedded printing has evolved into a versatile biofabrication platform used for the manufacturing of anatomically accurate tissue components, [17,18,19], [20] patterning of cellular spheroids, [21], [22] engineering of perfusable channels, [23,24,25] and investigation of cellgenerated forces.…”

Suppression of Filament Defects in Embedded 3D Printing

“…In contrast with the pinching experienced at low viscosity ratios, this high aspect ratio represents a separate mechanism, where the filament curls over on itself near the nozzle (Figure S7). These curling instabilities were documented in simulations of Newtonian inks and supports at high viscosity ratios, and they were more extensively explored via simulations and experiments in ref .…”

In-situ quality monitoring during embedded bioprinting using integrated microscopy and classical computer vision

“…Next, the melted agarose solution was placed on a magnetic stirrer at 700rpm for 3 hours while cooling to ambient room temperature. This method gives rise to a suspension of agarose particles as the polymer cools under shearing 16,17,19 . To create spherical particles, a batch emulsion method was used.…”

“…For example, a wide variety of manufacturing methods are used to create microparticles for granular hydrogels, which can result in significant differences in their rheological behaviour, along with the morphology of the particles themselves [16][17][18] . It has been demonstrated that increases in support hydrogel viscosity can improve print resolution, measured by quantifying the width of extruded filaments 9,14,19 . Similarly, lower viscosity in granular support hydrogels has been shown cause greater filament instability and buckling during deposition, particularly when the extrusion and nozzle translation speeds are not matched 19 .…”

“…It has been demonstrated that increases in support hydrogel viscosity can improve print resolution, measured by quantifying the width of extruded filaments 9,14,19 . Similarly, lower viscosity in granular support hydrogels has been shown cause greater filament instability and buckling during deposition, particularly when the extrusion and nozzle translation speeds are not matched 19 . However, it is not well understood how specific rheological parameters, driven by particle-particle interactions, can influence many print quality outcomes - particularly beyond relatively simple outcomes such as the diameter of extruded beams.…”