Abstract:
Crosslinked biopolymer networks are composed of filaments randomly distributed and crosslinked by specific binders, and are widespread in cytoskeletons of cells, biological gels and other natural materials. The binding energy of typical crosslinks in such biopolymer networks is relatively low and close to thermal energy, so that the binding status of the interaction is strongly influenced by the deformation of networks and thermal excitations from the environment. Experiments on different types of crosslinked biopolymer networks have demonstrated that these networks exhibit a linear response with low modulus in small deformation, and can be stiffened by more than two orders of magnitude in large strain. However, the network stiffness decreases dramatically when the applied strain exceeds a threshold value. This phenomenon is known as the transition from strain hardening to softening, and draws great attention from many researchers. Theoretical and numerical studies have indicated that such strain hardening is mainly caused by a transition from bending-dominated filament deformation in small strain to stretching-dominated response in large strain, and the strain softening is due to the microscopic unbinding of crosslinks, leading to weakened networks. This paper overviews the key components and representative architectures of crosslinked biopolymer networks, stretching behaviors of biopolymers, types and properties of crosslinks, and experimental methods used to measure the mechanical responses of network structures, with an emphasis on the theoretical, finite element and molecular dynamics models that pave the way to the understanding of the structure-function relations in crosslinked biopolymer networks.
