美国麻省理工学院McKinley, Gareth H.团队近日研究了复合水凝胶和软组织应变增强的普遍性。相关论文发表在2025年5月20日出版的《自然—物理学》杂志上。

软生物组织表现出的机械性能反映了它们嵌入生物聚合物基质中的细胞的复合结构。然而，它们独特的非线性机械响应背后的微观机制——其特征是压缩时的应变硬化，但剪切或拉伸时的应变软化——仍然知之甚少。研究组表明复合材料系统中的应变软化可能是由于塑性耗散引起的，这是由填料-聚合物相互作用介导的。 

研究组独立于这些塑性效应，对复合水凝胶和软组织的非线性弹性进行了表征，并表明它们的非线性弹性应变硬化是由底层生物聚合物基质的拉伸驱动的。因此，他们表明复合水凝胶和组织中的应变硬化是由压缩和剪切中普遍存在的应变放大因子介导的。

通过这样做，研究组证明了填料浓度和填料-聚合物相互作用强度等基本复合材料性能在介导复合材料系统应变硬化中的重要性。这些发现突出了关键的结构-性质关系，这些关系是复合凝胶和组织等生物相关软固体非线性力学的基础。

附：英文原文

Title: Strain-stiffening universality in composite hydrogels and soft tissues

Author: Song, Jake, Deiss-Yehiely, Elad, Yesilata, Serra, McKinley, Gareth H.

Issue&Volume: 2025-05-20

Abstract: Soft biological tissues exhibit mechanical properties that reflect their composite structure of cells embedded within a biopolymer matrix. However, the microscopic mechanisms underlying their unique nonlinear mechanical response—characterized by strain stiffening in compression, but strain softening in shear or tension—remain poorly understood. Here we show that strain softening in composite systems can arise due to plastic dissipation, which is mediated by filler–polymer interactions. We characterize the nonlinear elasticity of composite hydrogels and soft tissues in isolation from these plastic effects, and show that their nonlinear elastic strain stiffening is driven by the stretching of the underlying biopolymer matrix. We thus show that strain stiffening in composite hydrogels and tissues is mediated by strain amplification factors that are universal in compression and shear. In doing so, we demonstrate the importance of fundamental composite properties such as filler concentration and filler–polymer interaction strength in mediating strain stiffening in composite systems. These findings highlight key structure–property relationships that underlie the nonlinear mechanics of biologically relevant soft solids such as composite gels and tissues.

DOI: 10.1038/s41567-025-02869-x

Source: https://www.nature.com/articles/s41567-025-02869-x