Accurately characterizing the liver's mechanical properties is of paramount importance for disease diagnosis,treatment,surgical prosthetic modeling,and impact injury dummies.However,due to its inherent biological soft tissue nature,the characterization of mechanical behavior varies across testing methods and sample types.In this study,we employed transmission electron microscope and Micro CT to observe the morphology of the marginal and center of rat livers and conducted macroscopic mechanical tests to characterize their elasticity and viscoelasticity.The results revealed that the central region displayed higher metabolic levels,elongated mitochondria,and an abundance of rough endoplasmic reticulum at the microscale.At the mesoscale,larger diameter portal veins were mainly distributed in the central region,while smaller diameter arteries were predominantly located at the periphery.At the macroscale,under a strain rate of 0.0167 s^(-1),no significant differences were observed in the elastic properties between the two regions.However,as the strain rate increased up to 0.167 s^(-1),the central region displayed higher porosity,resulting in reduced liquid loss,increased hardness,and higher viscosity compared to the periphery.Consequently,the liver demonstrated overall heterogeneity,with isotropic models suitable for the peripheral region,while more intricate models may be required to capture the complexity of the central region with its intricate vasculature.
