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Tough hydrogels have emerged as a promising class of materials to target load‐bearing applications, where the material has to resist multiple cycles of extreme mechanical impact. A variety of chemical interactions and network architectures are used to enhance the mechanical properties and fracture mechanics of hydrogels making them stiffer and tougher. In recent years, the mechanical properties of tough, high‐performance hydrogels have been benchmarked, however, this is often incomplete as important variables like water content are largely ignored. In this review, the aim is to clarify the reported mechanical properties of state‐of‐the‐art tough hydrogels by providing a comprehensive library of fracture and mechanical property data. First, common methods for mechanical characterization of such high‐performance hydrogels are introduced. Then, various modes of energy dissipation to obtain tough hydrogels are discussed and used to categorize the individual datasets helping to asses the material's (fracture) mechanical properties. Finally, current applications are considered, tough high‐performance hydrogels are compared with existing materials, and promising future opportunities are discussed. [ABSTRACT FROM AUTHOR]

Abstract Tough hydrogels have emerged as a promising class of materials to target load‐bearing applications, where the material has to resist multiple cycles of extreme mechanical impact. A variety of chemical interactions and network architectures are used to enhance the mechanical properties and fracture mechanics of hydrogels making them stiffer and tougher. In recent years, the mechanical properties of tough, high‐performance hydrogels have been benchmarked, however, this is often incomplete as important variables like water content are largely ignored. In this review, the aim is to clarify the reported mechanical properties of state‐of‐the‐art tough hydrogels by providing a comprehensive library of fracture and mechanical property data. First, common methods for mechanical characterization of such high‐performance hydrogels are introduced. Then, various modes of energy dissipation to obtain tough hydrogels are discussed and used to categorize the individual datasets helping to asses the material's (fracture) mechanical properties. Finally, current applications are considered, tough high‐performance hydrogels are compared with existing materials, and promising future opportunities are discussed.

Biological tissues hinge on blood perfusion and mechanical toughness to function. Injectable hydrogels that possess both high permeability and toughness have profound impacts on regenerative medicine but remain a long‐standing challenge. To address this issue, injectable, pore‐forming double‐network hydrogels are fabricated by orchestrating stepwise gelation and phase separation processes. The interconnected pores of the resulting hydrogels enable direct medium perfusion through organ‐sized matrices. The hydrogels are amenable to cell encapsulation and delivery while promoting cell proliferation and spreading. They are also pore insensitive, tough, and fatigue resistant. When tested in biomimetic perfusion bioreactors, the hydrogels maintain physical integrity under prolonged, high‐frequency biomechanical stimulations (>6000 000 cycles at 120 Hz). The excellent biomechanical performance suggests the great potential of the new injectable hydrogel technology for repairing mechanically dynamic tissues, such as vocal folds, and other applications, such as tissue engineering, biofabrication, organs‐on‐chips, drug delivery, and disease modeling. [ABSTRACT FROM AUTHOR]