Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia.
Department of Physiology, Monash University, Clayton, VIC 3800, Australia.
Acta Biomater. 2015 Jul;21:132-41. doi: 10.1016/j.actbio.2015.03.028. Epub 2015 Mar 31.
Understanding the heterogeneity of biological structures, particularly at the micro/nano scale can offer insights valuable for multidisciplinary research in tissue engineering and biomimicry designs. Here we propose to combine nanocharacterisation tools, particularly Focused Ion Beam (FIB) and Atomic Force Microscopy (AFM) for three dimensional mapping of mechanical modulus and chemical signatures. The prototype platform is applied to image and investigate the fundamental mechanics of the rat face whiskers, a high-acuity sensor used to gain detailed information about the world. Grazing angle FIB milling was first applied to expose the interior cross section of the rat whisker sample, followed by a "lift-out" method to retrieve and position the target sample for further analyses. AFM force spectroscopy measurements revealed a non-uniform pattern of elastic modulus across the cross section, with a range from 0.8GPa to 13.5GPa. The highest elastic modulus was found at the outer cuticle region of the whisker, and values gradually decreased towards the interior cortex and medulla regions. Elemental mapping with EDS confirmed that the interior of the rat whisker is dominated by C, O, N, S, Cl and K, with a significant change of elemental distribution close to the exterior cuticle region. Based on these data, a novel comprehensive three dimensional (3D) elastic modulus model was constructed, and stress distributions under realistic conditions were investigated with Finite Element Analysis (FEA). The simulations could well account for the passive whisker deflections, with calculated resonant frequency as well as force-deflection for the whiskers being in good agreement with reported experimental data. Limitations and further applications are discussed for the proposed FIB/AFM approach, which holds good promise as a unique platform to gain insights on various heterogeneous biomaterials and biomechanical systems.
理解生物结构的异质性，特别是在微/纳米尺度上，可以为组织工程和仿生设计的多学科研究提供有价值的见解。在这里，我们建议将纳米特性化工具，特别是聚焦离子束（FIB）和原子力显微镜（AFM）结合起来，用于机械模量和化学特征的三维映射。该原型平台应用于成像和研究大鼠面部触须的基本力学，大鼠触须是一种高灵敏度传感器，用于获取有关世界的详细信息。首先应用掠入射 FIB 铣削来暴露大鼠胡须样品的内部横截面，然后采用“取出”方法来检索和定位目标样品以进行进一步分析。AFM 力谱测量显示出横跨横截面的弹性模量的非均匀模式，范围从 0.8GPa 到 13.5GPa。在胡须的外角质层区域发现了最高的弹性模量，并且值逐渐向内部皮质和髓质区域降低。EDS 元素映射证实大鼠胡须的内部主要由 C、O、N、S、Cl 和 K 组成，在接近外部角质层区域的地方，元素分布有显著变化。基于这些数据，构建了一种新颖的综合三维（3D）弹性模量模型，并通过有限元分析（FEA）研究了实际条件下的应力分布。模拟可以很好地解释被动胡须的挠度，计算出的共振频率以及胡须的力-挠度与报道的实验数据非常吻合。讨论了所提出的 FIB/AFM 方法的局限性和进一步的应用，该方法有望成为一种独特的平台，可以深入了解各种异质生物材料和生物力学系统。
