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Hydrogels are candidate building blocks in a wide range of biomaterial applications including soft and biohybrid robotics, microfluidics, and tissue engineering. Recent advances in embedded 3D printing have broadened the design space accessible with hydrogel additive manufacturing. Specifically, the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) technique has enabled the fabrication of complex 3D structures using extremely soft hydrogels, e.g., alginate and collagen, by assembling hydrogels within a fugitive support bath. However, the low structural rigidity of FRESH printed hydrogels limits their applications, especially those that require operation in nonaqueous environments. In this study, we demonstrated long-fiber embedded hydrogel 3D printing using a multihead printing platform consisting of a custom-built fiber extruder and an open-source FRESH bioprinter with high embedding fidelity. Using this process, fibers were embedded in 3D printed hydrogel components to achieve significant structural reinforcement (e.g., tensile modulus improved from 56.78 ± 8.76 to 382.55 ± 25.29 kPa and tensile strength improved from 9.44 ± 2.28 to 45.05 ± 5.53 kPa). In addition, we demonstrated the versatility of this technique by using fibers of a wide range of sizes and material types and implementing different 2D and 3D embedding patterns, such as embedding a conical helix using electrochemically aligned collagen fiber via nonplanar printing. Moreover, the technique was implemented using low-cost material and is compatible with open-source software and hardware, which facilitates its adoption and modification for new research applications.
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Printable homocomposite hydrogels with synergistically reinforced molecular-colloidal networks
Abstract The design of hydrogels where multiple interpenetrating networks enable enhanced mechanical properties can broaden their field of application in biomedical materials, 3D printing, and soft robotics. We report a class of self-reinforced homocomposite hydrogels (HHGs) comprised of interpenetrating networks of multiscale hierarchy. A molecular alginate gel is reinforced by a colloidal network of hierarchically branched alginate soft dendritic colloids (SDCs). The reinforcement of the molecular gel with the nanofibrillar SDC network of the same biopolymer results in a remarkable increase of the HHG’s mechanical properties. The viscoelastic HHGs show >3× larger storage modulus and >4× larger Young’s modulus than either constitutive network at the same concentration. Such synergistically enforced colloidal-molecular HHGs open up numerous opportunities for formulation of biocompatible gels with robust structure-property relationships. Balance of the ratio of their precursors facilitates precise control of the yield stress and rate of self-reinforcement, enabling efficient extrusion 3D printing of HHGs.
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- Award ID(s):
- 1825476
- PAR ID:
- 10228262
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 12
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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