3D Printing of Strong and Tough Double Network Granular Hydrogels

Abstract

Many soft natural tissues display a fascinating set of mechanical properties that remains unmatched by manmade counterparts. These unprecedented mechanical properties are achieved through an intricate interplay between the structure and locally varying the composition of these natural tissues. This level of control cannot be achieved in soft synthetic materials. To address this shortcoming, a novel 3D printing approach to fabricate strong and tough soft materials is introduced, namely double network granular hydrogels (DNGHs) made from compartmentalized reagents. This is achieved with an ink composed of microgels that are swollen in a monomer‐containing solution; after the ink is additive manufactured, these monomers are converted into a percolating network, resulting in a DNGH. These DNGHs are sufficiently stiff to repetitively support tensile loads up to 1.3 MPa. Moreover, they are more than an order of magnitude tougher than each of the pure polymeric networks they are made from. It is demonstrated that this ink enables printing macroscopic, strong, and tough objects, which can optionally be rendered responsive, with high shape fidelity. The modular and robust fabrication of DNGHs opens up new possibilities to design adaptive, strong, and tough hydrogels that have the potential to advance, for example, soft robotic applications.

From vesicles to materials: bioinspired strategies for fabricating hierarchically structured soft matter

“…This procedure offers the distinct advantage that the inter-particle links are not confined to the grain boundaries but are part of the percolating network that penetrates the grains and grain boundaries. This percolating network imparts to the granular hydrogels the highest stiffness that has been reported for three-dimensionally printed hydrogels [69]. This method might point towards a promising direction to develop nature-inspired processes that result in materials possessing mechanical properties that more closely resemble or even exceed those of natural counterparts, as alluded to in figure 3 g–k .…”

“…( d – f ) Solidification of the granular superstructures. The inter-particle adhesion can be improved by crosslinking them through ( d ) host-guest chemistries, [67] ( e ) covalent bonds, [68] or ( f ) a covalent percolating network that penetrates the grains and simultaneously spans the grain boundaries [69]. ( g – k ) Applications of granular materials.…”

“…( g – k ) Applications of granular materials. Inks composed of jammed compartments can be three-dimensionally printed into ( g ) organs such as an ear, [70] ( h ) femur, [71] ( i ) cm-sized cups, [72] ( j ) bands that bear pressures up to 1.3 MPa even under tension, [69] and ( k ) shape-morphing materials [69]. With permissions of John Wiley and Sons, Royal Society of Chemistry, Elsevier, ACS, and the Creative Common license.…”

Anisotropic Rod-Shaped Particles Influence Injectable Granular Hydrogel Properties and Cell Invasion

“…[12,13] Thus, granular hydrogels are ideally suited to promote the invasion of cells and blood vessels when used as injectable scaffolds for tissue repair. These desirable characteristics have motivated the development and application of granular hydrogels towards various biomedical applications including drug delivery, [14,15] immune modulation, [13,16] modular fabrication of biomaterials including with 3D printing, [17–19] and as cell-instructive scaffolds. [20–22]…”

Rapid Fabrication of Patterned Gels via Microchannel‐Conformal Frontal Polymerization

“…[1][2][3][4][5][6][7] Especially, the manipulation of gels with specific shape and structural complexity is gaining prominence to satisfy advanced applications. [8][9][10] To this end, new facile and effective strategy aiming at diversified structure is highly desirable. In addition, the incorporation of fluorescent nano-materials into gels has attracted increasing attention, which renders the hybrid material with superior properties.…”