Jammed Microgel Inks for 3D Printing Applications

Abstract

Abstract3D printing involves the development of inks that exhibit the requisite properties for both printing and the intended application. In bioprinting, these inks are often hydrogels with controlled rheological properties that can be stabilized after deposition. Here, an alternate approach is developed where the ink is composed exclusively of jammed microgels, which are designed to incorporate a range of properties through microgel design (e.g., composition, size) and through the mixing of microgels. The jammed microgel inks are shear‐thinning to permit flow and rapidly recover upon deposition, including on surfaces or when deposited in 3D within hydrogel supports, and can be further stabilized with secondary cross‐linking. This platform allows the use of microgels engineered from various materials (e.g., thiol‐ene cross‐linked hyaluronic acid (HA), photo‐cross‐linked poly(ethylene glycol), thermo‐sensitive agarose) and that incorporate cells, where the jamming process and printing do not decrease cell viability. The versatility of this particle‐based approach opens up numerous potential biomedical applications through the printing of a more diverse set of inks.

Recent advances in shear‐thinning and self‐healing hydrogels for biomedical applications

“…The injectable characteristics of granular hydrogels have also been exploited in 3D printing techniques, where bioinks can be comprised of heterogeneous populations of particles . With no further modifications of materials, jammed microgel systems offer a new approach to biofabrication and expand on the availability of inks for printing.…”

From Shape to Function: The Next Step in Bioprinting

“…The scale bar represents 5 mm. Reproduced under the terms of the Creative Commons CC‐BY 4.0 License ( https://creativecommons.org/licenses/by/4.0/) . Copyright 2019, The Authors, Published by Wiley‐VCH.…”

“…Noncovalent, supramolecular interactions between covalently bound polymer chains have also been used to develop bioinks based on physical gels. In particular, host–guest interactions have been applied to design bioinks with defined properties . Blends of HA functionalized with either adamantane or β‐cyclodextrin form shear thinning and self‐healing hydrogels based on reversible host–guest complexes between the two functional groups .…”

Additive Manufacturing of Precision Biomaterials

“…These properties have been studied extensively for jammed colloids and have been exploited for AM of silica dispersion inks . More recently, this approach has been extended to jammed microgel inks for using in robotic dispensing . In this approach, microgels were synthesized using microfluidics that were concentrated to produce a viscoelastic solid.…”

“…Without any engineered interactions between particle surfaces, the jammed granular ink formed a viscoelastic material with shear‐thinning and self‐healing properties amenable to extrusion‐based AM. While the jammed granular inks form free‐standing solids after extrusion, the materials, in some instances, were reinforced with photoinduced cross‐linking to generate granular elastic solids . In other approaches, injectable granular materials have been engineered exploiting supramolecular or ionic binding interactions between constituent microgels …”