Tensile tests have been extensively used for the characterization of tough hydrogels and are commonly carried out on a universal testing machine. In a typical tensile test experiment, a dumbbell-shaped hydrogel specimen (sometimes referred to as dogbone) is clamped with a fixed distance L 0 also known as gauge length (Figure ). Next, the tensile force is recorded while one clamp is displaced with a constant velocity resulting in an elongation L of the deforming sample. The tensile strain ε can be calculated either from the stretch ratio λ or directly through L and L 0 according to