出处： 2018 Investigation of micromechanical properties of hard sphere filled composite hydrogels by atomic force microscopy and finite element simulations

Abstract

概述
Atomic force microscopy (AFM) indentation is the most suitable way to characterize micromechanical properties of soft materials such as bio tissues.
一个转折表示现在面临的困难
However, the mechanical data obtained from force-indentation measurement are still not well understood due to complex geometry of the bio tissue, nonlinearity of indentation contact, and constitutive relation of hyperelastic soft material. Poly-N-isopropyl acrylamide (PNIPAM) filled with 5 wt. % polystyrene (PS) sphere particles material system can be utilized as a simplified model for mimicking a whole host of soft materials.
介绍方法已有的发展
Finite element model has been constructed to simulate indentation as in AFM experiments using colloidal probes for a parametric study, with the main purpose of understanding the effect of particles on overall behavior of mechanical data and local deformation field under indentation contact.
介绍方法的优点
Direct comparison between finite element simulation and indentation data from AFM experiments provides a powerful method to characterize soft materials properties quantitatively, addressing the lack of analytical solutions for hard-soft composites, both biological and synthetic ones.
介绍文章工作
In this framework, quantitative relations are found between the depth, at which the particle was embedded, the particle size and the elastic modulus of the overall composite. Comprehensive characterizations were established to distinguish indentation on a particle residing on top of the hydrogel from a particle embedded inside the hydrogel matrix. Finally, different assumptions of interface friction at the boundary between the particle and the hydrogel have been tested and directly compared with experimental measurements.

Keywords

Composite hydrogels; atomic force microscope; finite element simulation; mechanical properties; spherical particles; hyperelastic material

译文

原子力显微镜(AFM)压痕是表征生物组织等软质材料微观力学性能的最合适方法。然

而，由于生物组织的复杂几何结构、压痕接触的非线性以及超弹性软材料的本构关系，力-压痕测量得到的力学数据仍不清楚。聚- n -异丙基丙烯酰胺(PNIPAM)填充5 wt. %聚苯乙烯(PS)球形颗粒材料体系可以作为一种简化模型来模拟整个软质材料。建立了有限元模型，模拟压痕与原子力显微镜实验中使用胶体探针进行参数化研究，主要目的是了解颗粒对压痕接触下力学数据整体行为和局部变形场的影响。

有限元模拟与AFM实验压痕数据的直接比较提供了一种定量表征软材料性能的强大方法，解决了软硬复合材料(包括生物和合成材料)缺乏解析解的问题。

在此框架下，发现了颗粒嵌入深度、颗粒尺寸与整体复合材料弹性模量之间的定量关系。建立了综合表征，以区分位于水凝胶顶部的颗粒上的压痕与嵌入在水凝胶基质内的颗粒。最后，对颗粒与水凝胶边界处界面摩擦的不同假设进行了测试，并与实验测量结果进行了直接比较。

关键词:复合水凝胶;原子力显微镜;有限元模拟;机械性能;球形颗粒;超弹性的材料