Microstructure-based constitutive models have been adopted in recent studies of non-linear mechanical properties of biological soft tissues. These models provide more accurate predictions of the overall mechanical responses of tissues than phenomenological approaches. Based on standard approximations in non-linear mechanics, we classified the microstructural models into three categories: (1) uniform-field models with solid-like matrix, (2) uniform-field models with fluid-like matrix, and (3) second-order estimate models. The first two categories assume affine deformation field where the deformation of microstructure is the same as that of the tissue, regardless of material heterogeneities; i.e., they represent the upper bounds of the exact effective strain energy and stress of soft tissues. In addition, the first type is not purely structurally motivated and hence cannot accurately predict the microscopic mechanical behaviors of soft tissues. The third category considers realistic geometrical features, material properties of microstructure and interactions among them and allows for flexible deformation in each constituent. The uniform-field model with fluid-like matrix and the second-order estimate model are microstructure-based, and can be applied to different tissues based on micro-structural features.

在最近的生物软组织非线性力学特性研究中，已经采用了基于微结构的本构模型。与现象学方法相比，这些模型对组织的整体机械反应提供了更准确的预测。基于非线性力学中的标准近似，我们将微观结构模型分为三类：（1）具有类固体基质的均匀场模型，（2）具有类流体基质的均匀场模型，以及（3）第二类-阶估计模型。前两类假设仿射变形场，其中微观结构的变形与组织的变形相同，而与材料的异质性无关；即，它们代表了软组织的准确有效应变能和应力的上限。此外，第一种类型并非纯粹出于结构动机，因此无法准确预测软组织的微观力学行为。第三类考虑现实的几何特征、微观结构的材料特性以及它们之间的相互作用，并允许每个成分的灵活变形。具有类流体矩阵的均匀场模型和二阶估计模型是基于微观结构的，可以根据微观结构特征应用于不同的组织。