3D Printing Method for Tough Multifunctional Particle-Based Double-Network Hydrogels

Abstract

3D printing of hydrogels finds widespread applications in biomedicine and engineering. Artificial cartilages and heart valves, tissue regeneration and soft robots, require high mechanical performance of complex structures. Although many tough hydrogels have been developed, complicated synthesis processes hinder their fabrication in 3D printing. Here, a strategy is proposed to formulate hydrogel inks, which can be printed into various strong and tough particle-based double-network (P-DN) hydrogels of arbitrary shapes without any rheological modifiers. These hydrogel inks consist of microgels and a hydrogel precursor. The microgels are individual highly cross-linked networks. They are prepared by swelling dried microparticles in the hydrogel precursor that consists of monomers, initiators, and cross-linkers. Microgels regulate the rheological properties of the hydrogel ink and enable the direct printing. After printing and curing, the precursor forms a sparsely cross-linked network that integrates the microgels, leading to a P-DN hydrogel. The proposed hydrogel inks allow 3D printing of multifunctional hydrogel structures with high mechanical performance and strong adhesion to diverse materials. This strategy will open new avenues to fabricate multifunctional devices in tissue engineering and soft robotics.

Generalizing hydrogel microparticles into a new class of bioinks for extrusion bioprinting

“…HMPs remain intact during the entire process because of the stable inner-particle covalent network, protecting encapsulated cells from high shear stress and further enhancing printing stability. Their shear-thinning property is independent from the polymers and chemistries used to construct the HMPs and has been verified in a wide range of material formulations, including silica ( 14 ), hyaluronic acid ( 11 ), agarose ( 11 ), poly(ethylene glycol) (PEG) ( 12 ), chitosan ( 15 ), gelatin ( 16 ), and 2-acrylamido-2-methylpropane sulfonic acid ( 17 , 18 ). Printed HMP constructs can be further annealed via various secondary cross-linking strategies to improve their mechanical properties and stretchability ( 12 , 16 – 18 ).…”

3D Printing of Conductive Hydrogel–Elastomer Hybrids for Stretchable Electronics

“…Unfortunately, the compatibility between these conductive materials and the surrounding insulating substrate (e.g., elastomer) still has profound challenges, which results in a mechanical mismatch and hard–soft materials’ interfacial delamination. Comparatively, conductive hydrogels which have distinctive attributes including high stretchability, biocompatibility, and easy fabrications have emerged as promising conducting materials for stretchable electronics. − In general, the conductivity of electronic devices should be better through electron carriers because ionic transportation lacks electronic conductivity, and the slow ion migration leads to a slow response. The electrical conduction of hydrogels is usually obtained by mixing a conductive polymer in a hydrogel matrix and the conduction is induced by electron transport.…”

Solvent‐Cast‐Assisted Printing of Biomimetic Morphing Hydrogel Structures with Solvent Evaporation‐Induced Swelling Mismatch

“…[ 21,22 ] The printed hydrogels are usually mechanically weak, and the applications are limited in tissue engineering, especially for load‐bearing purposes. To improve the mechanical properties of the printed gel structures, additional polymerization to form a second network [ 23–25 ] or a soaking step to form coordination bonds [ 26,27 ] is usually adopted. However, these approaches are only applicable for specific systems, and the compositions of the gels have been changed by this additional step.…”