Lee Donghee, Ryu Sangjin
Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 e-mail:
J Biomech Eng. 2017 Apr 1;139(4). doi: 10.1115/1.4035536.
The elasticity of soft biological materials is a critical property to understand their biomechanical behaviors. Atomic force microscopy (AFM) indentation method has been widely employed to measure the Young's modulus (E) of such materials. Although the accuracy of the method has been recently evaluated based on comparisons with macroscale E measurements, the repeatability of the method has yet to be validated for rigorous biomechanical studies of soft elastic materials. We tested the AFM indentation method using colloidal probes and polyacrylamide (PAAM) gels of E < 20 kPa as a model soft elastic material after having identified optimal trigger force and probe speed. AFM indentations repeated with time intervals show that the method is well repeatable when performed carefully. Compared with the rheometric method and the confocal microscopy indentation method, the AFM indentation method is evaluated to have comparable accuracy and better precision, although these elasticity measurements appear to rely on the compositions of PAAM gels and the length scale of measurement. Therefore, we have confirmed that the AFM indentation method can reliably measure the elasticity of soft elastic materials.
软生物材料的弹性是理解其生物力学行为的关键特性。原子力显微镜（AFM）压痕法已被广泛用于测量此类材料的杨氏模量（E）。尽管最近已通过与宏观尺度E测量值的比较来评估该方法的准确性，但对于软弹性材料的严格生物力学研究，该方法的可重复性尚未得到验证。在确定了最佳触发力和探针速度后，我们使用胶体探针和E<20 kPa的聚丙烯酰胺（PAAM）凝胶作为模型软弹性材料测试了AFM压痕法。随时间间隔重复进行的AFM压痕表明，该方法在仔细操作时具有良好的可重复性。与流变测量法和共聚焦显微镜压痕法相比，尽管这些弹性测量似乎依赖于PAAM凝胶的组成和测量的长度尺度，但AFM压痕法被评估为具有相当的准确性和更好的精度。因此，我们已经证实AFM压痕法能够可靠地测量软弹性材料的弹性。
