Journal of the Mechanical Behavior of Biomedical Materials ( IF 3.9 ) Pub Date : 2017-10-31 , DOI: 10.1016/j.jmbbm.2017.10.035 Guanlin Tang , Massimiliano Galluzzi , Chandra Sekhar Biswas , Florian J. Stadler
Atomic force microscopy (AFM) indentation is the most suitable way to characterize micromechanical properties of soft materials such as bio tissues. 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. 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. 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. 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.
中文翻译:
硬球填充复合水凝胶的微机械性能的原子力显微镜和有限元模拟研究
原子力显微镜(AFM)压痕是表征软材料(如生物组织)的微机械性能的最合适方法。然而,由于生物组织的复杂几何形状,压痕接触的非线性以及超弹性软材料的本构关系,从力压痕测量获得的机械数据仍未得到很好的理解。填充有5 wt%聚苯乙烯(PS)球形颗粒材料系统的聚N-异丙基丙烯酰胺(PNIPAM)可以用作模拟整个软材料主体的简化模型。已经建立了有限元模型来模拟压痕,如AFM实验中那样,使用胶体探针进行参数研究,主要目的是了解颗粒对压痕接触下力学数据和局部变形场的整体行为的影响。有限元模拟和AFM实验的压痕数据之间的直接比较提供了一种强大的方法来定量表征软材料的特性,解决了生物和合成硬质复合材料缺乏分析解决方案的问题。在此框架中,发现了颗粒嵌入的深度,颗粒大小和整个复合材料的弹性模量之间的定量关系。建立了全面的表征,以区分位于水凝胶顶部的颗粒与嵌入在水凝胶基质内部的颗粒的压痕。最后,