Fiber-reinforced tough hydrogels

Abstract

Using strong fibers to reinforce a hydrogel is highly desirable but difficult. Such a composite would combine the attributes of a solid that provides strength and a liquid that transports matter. Most hydrogels, however, are brittle, allowing the fibers to cut through the hydrogel when the composite is loaded. Here we circumvent this problem by using a recently developed tough hydrogel. We fabricate a composite using an alginate-polyacrylamide hydrogel reinforced with a random network of stainless steel fibers. Because the hydrogel is tough, the composite does not fail by the fibers cutting the hydrogel; instead, it fails by the fibers pulling out of the hydrogel against friction. Both stiffness and strength can be increased significantly by adding fibers to the hydrogel. Before failure the composite dissipates a significant amount of energy, at a tunable level of stress, attaining large deformation. Potential applications of tough hydrogel composites include energy-absorbing helmets, tendon repair surgery, and stretchable biometric sensors.

Role of Biomaterials and Controlled Architecture on Tendon/Ligament Repair and Regeneration

“…Thus, engineers, researchers, and clinicians are at a stage where these findings can be combined to develop suitable “fiber‐reinforced hydrogel” (FRH) composites for suitable T/L constructs that are sufficiently strong to support human T/L repair but also biologically active to support appropriate ECM integration. The concept of FRH as a biomaterial has been explored recently, with the incorporated fibers enhancing the strength, modulus, and toughness of the hydrogels in the direction or directions of fiber alignment, similar to the effects observed in composites such as reinforced concrete and fiber‐reinforced composite structures. The fibers or fiber scaffolds are initially produced commonly through electrospinning or more recently melt‐electrowriting for more controlled structures.…”

Energy‐Dissipative Matrices Enable Synergistic Toughening in Fiber Reinforced Soft Composites

“…Based on this concept, some attempts have been made to fabricate fiber reinforced hydrogel composites. [24][25][26][27][28][29] Utilizing this technique, researchers have been able to increase and tune the stiffness and toughness achievable with hydrogel-based systems. However, developing soft composites with synergistically improved mechanical properties, such as those seen in hard bioinspired composites, is still a challenge.Recently, our group has developed a new class of tough hydrogels, polyampholyte (PA) gels (fracture energy, T = 3000 J m −2 ), based on multiple ionic bonds acting as reversible sacrificial bonds in the gel network.…”

“…Based on this concept, some attempts have been made to fabricate fiber reinforced hydrogel composites. [24][25][26][27][28][29] Utilizing this technique, researchers have been able to increase and tune the stiffness and toughness achievable with hydrogel-based systems. However, developing soft composites with synergistically improved mechanical properties, such as those seen in hard bioinspired composites, is still a challenge.…”

Nanofiber‐Based Hydrogels: Controllable Synthesis and Multifunctional Applications

“…Hydrogels with crosslinked 3D water‐locking networks have gained widespread attractions attributing to their outstanding characteristics including superhydrophilicity, high water‐holding capacity, excellent biocompatibility, as well as their wide utilizations in various fields involving food production, tissue engineering, wound dressings, drug carriers, flexible sensors, soft devices, and so on . Generally, the performance of hydrogel materials mainly depends on two critical factors, one is the high liquid content which benefits for the substance transfer, the other one is the high mechanical strength of the solid phase network that decides the structural stability of the hydrogels . To satisfy the first requirement of high liquid content, a series of hydrogel materials with a ultrahigh water content have been developed, such as supramolecular hydrogels, carboxymethyl cellulose hydrogels, clay nanosheet hydrogels, graphene/hemoglobin composite gels .…”

“…[1][2][3] Generally, the performance of hydrogel materials mainly depends on two critical factors, one is the high liquid content which benefits for the substance transfer, the other one is the high mechanical strength of the solid phase network that decides the structural stability of the hydrogels. [4,5] To satisfy the first requirement of high liquid content, a series of hydrogel materials with a ultrahigh water content have been developed, such as supramolecular hydrogels, carboxymethyl cellulose hydrogels, clay nanosheet nanotechnology and materials science, unremitting efforts have focused on the structure and composition design for achieving advanced nanofiber-based hydrogels (NFHGs) with high mechanical strength and multifunctional application performance.…”