Anisotropic and layer-specific biomechanical characterization of descending thoracic aortic tissues using mirror-assisted dual-surface DIC

Abstract Aortic tissue is a collagen fiber-reinforced multilayer composite material with each layer indicating diverse hyperelastic and viscoelastic properties, whose alterations could be indicators of the formation and progression of aortic lesions. Up to now, numerous studies have employed diverse in vitro mechanical tests to derive the mechanical and structural properties of aortic tissues, reporting various testing and measuring systems for assessing aortic hyperelasticity and viscoelasticity. However, a new measuring device and algorithm procedure allowing three-layer hyper-viscoelastic and morphological parameter identification of the intact aortic wall is necessitated to provide a more comprehensive understanding of the anisotropic and layer-specific aortic biomechanics. In this study, a testing and measuring system integrating a desktop mechanical testing machine and a 90°mirror-assisted dual-surface digital image correlation (DIC) system was developed to investigate the complex biomechanics of descending thoracic aortic tissues. Spatiotemporal dual-surface displacement and strain maps of the aortic intima and adventitia were reconstructed during uniaxial tension tests and subsequent stress relaxation tests. Based on the DIC measurements, the anisotropic and layer-specific hyper-viscoelastic properties and morphological features of the aorta wall were estimated using the finite element model updating (FEMU) method. This study provides a novel methodology for investigating the complex nonlinear biomechanics of aortic tissue, contributing insights into the anisotropy and layer specificity in biomechanical and morphological properties of the aortic wall during biomechanical modeling.