Mechanical Properties of Multifunctional Hydrogels

Hydrogels are 3D cross-linked polymeric networks with the ability to hold huge amounts of water that are applicable in several industrial and biotechnological research areas. Regarding the defined application, the performance of the hydrogels is strongly influenced by their mechanical properties. Therefore, there has been a great effort in the investigation of mechanical features of the hydrogels, from microscale to macroscale, to create desirable characteristics for any given application. To understand the mechanical behavior, it is important to address the theories for determining the characteristics of hydrogels and models for testing them. This chapter is mainly focused on the theoretical models and experimental methods to identify mechanical behavior of hydrogels. In detail, the models including rubber elasticity and viscoelasticity have been elucidated. In addition, experimental methods including stress-strain tests, creep and stress relaxation, cyclic deformations, and dynamic mechanical analysis have been explained. Besides, network models and strategies to alter the micro and macro structure of hydrogels, and material addition for tunning and controlling the mechanical features, by emphasizing the relationship of structure-activity, have been clarified. Finally, the mechanoresponsive hydrogels for biomedical applications are discussed.