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Abstract Blood clotting is the body’s natural reaction in wound healing and is also the cause of many pathologies. Fibrin – the main protein in the clotting process provides clots’ mechanical strength by forming a scaffold of complex fibrin fibers. Fibrin fibers exhibit high extensibility and primarily elastic properties under static loading, which differ from in vivo dynamic forces. In many biological materials, the mechanical response changes under repeated loading/unloading (cyclic loading). Using lateral force microscopy, we show fibrin fibers possess viscoelastic behavior and experience irreversible damage under cyclic loading. Cross-linking results in a more rigid structure with permanent damage occurring mostly at larger strains, which is corroborated by computational modeling of fibrin extension using a hyperelastic model. Molecular spectroscopy analysis with broadband coherent anti-Stokes Raman scattering spectroscopy in addition to molecular dynamic simulations allow identification of the source of damage, the unfolding pattern, and inter and intramolecular changes in fibrin. The results show partial recovery of protein’s secondary and tertiary structures under load, providing deeper understanding of fibrin’s unique behavior in wound healing or pathologies like stroke and embolism. 

Constitutive models are important to biomechanics for two key reasons. First, constitutive modelling is an essential component of characterizing tissues’ mechanical properties for informing theoretical and computational models of biomechanical systems. Second, constitutive models can be used as a theoretical framework for extracting and comparing key quantities of interest from material characterization experiments. Over the past five decades, the Ogden model has emerged as a popular constitutive model in soft tissue biomechanics with relevance to both informing theoretical and computational models and to comparing material characterization experiments. The goal of this short review is threefold. First, we will discuss the broad relevance of the Ogden model to soft tissue biomechanics and the general characteristics of soft tissues that are suitable for approximating with the Ogden model. Second, we will highlight exemplary uses of the Ogden model in brain tissue, blood clot and other tissues. Finally, we offer a tutorial on fitting the one-term Ogden model to pure shear experimental data via both an analytical approximation of homogeneous deformation and a finite-element model of the tissue domain. Overall, we anticipate that this short review will serve as a practical introduction to the use of the Ogden model in biomechanics. This article is part of the theme issue ‘The Ogden model of rubber mechanics: Fifty years of impact on nonlinear elasticity’.