Fundamentals of double network hydrogels

Abstract

Double network (DN) hydrogels as promising soft-and-tough materials intrinsically possess extraordinary mechanical strength and toughness due to their unique contrasting network structures, strong interpenetrating network entanglement, and efficient energy dissipation.

Possible Application of Tough Hydrogel in Machinery

“…Like a liquid, small molecules diffuse through a hydrogel. Hydrogels are currently viewed as waterinsoluble soft and wet materials, and they are usually composed of three-dimensional polymer network structure and a large amount of water (50 ~ 99%) [1]. It has potential applications in many fields, such as, drug delivery system, superabsorbent, biosensor, tissue engineering, wound dressing, and battery.…”

Hydrogels and bioreactors for cartilage research and functional tissue engineering

“…Yet, they often involve toxic chemicals and lengthy fabrication processes which severely limits their cytocompatibility. Accordingly, their suitability for cell encapsulation, direction of tissue-specific cell differentiation, ECM accumulation, as well as enzymatic degradation remains largely unexplored [194]. Only a few instances of cell-laden double-network gels have been reported [195][196][197][198]; however, most of these studies only demonstrated short-term cytocompatibility, while a functional assessment of neotissue formation and mechanical properties has rarely been performed.…”

“…However, the use of conventional hydrogels for tissue engineering of load-bearing tissues is severely limited by their high brittleness, lack of effective energy dissipation, and inadequate toughness [194].…”

“…Fibre-reinforcement of hydrogels was previously shown to greatly enhance stiffness under low compressive strains whilst retaining bioactivity, as well as cyto-and biocompatibility; however, these constructs are brittle and cannot sustain large compressive strains without failure [163]. Synthetic DN hydrogels, on the other hand, exhibit high mechanical strength and capability to resist large deformations and stresses (fracture compressive stress of 17.2 MPa and strain of 92 %) [193], but their suitability for cell encapsulation, direction of tissuespecific cell differentiation, extracellular matrix accumulation, as well as enzymatic degradation remains largely unexplored [194].…”

“…This may stem from the synthetic nature of most previously described DN gels which allow for fabrication of composites with extreme stiffness and ultimate mechanical strength [193,194,357], but often lack bioactivity and do not allow for cell-encapsulation due to harsh crosslinking conditions, thus making them better candidates for substitutes of load-bearing tissues rather than true tissue engineering scaffolds. Only a few instances of cell-laden DN gels have been reported [195][196][197][198], most of which were based on a combination of biopolymers, or a blend of a bio-and synthetic polymers.…”