Microscale Creep and Stress Relaxation Experiments with Individual Collagen Fibrils.
Microscale Creep and Stress Relaxation Experiments with Individual Collagen Fibrils.
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DOI：
10.1016/j.optlaseng.2021.106869
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发表时间：
2022-03
影响因子：
4.6
通讯作者：
Fan Yang;D. Das;I. Chasiotis
中科院分区：
文献类型：
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作者：
Fan Yang;D. Das;I. Chasiotis
纳米级大分子生物结构表现出时间依赖性的机械行为，但其蠕变和应力松弛行为的定量理解仍然难以捉摸，这主要是由于在保证其分子完整性的条件下获得足够的空间和时间分辨率以及控制应力或应变的实验挑战。为了解决这一差距，开发了一种实验方法来进行蠕变和应力松弛实验与个别哺乳动物胶原纤维。一种基于图像的边缘检测方法，实现了高放大倍数的光学显微镜和闭环比例积分微分（PID）控制相结合，实施和校准，以施加恒定的力或拉伸比，通过微机电系统（MEMS）设备的个人胶原纤维。这种实验方法允许实时控制单轴拉伸应力或应变，位移精度约为25 nm。整个实验系统被调整为适用于阶跃输入的上升时间低于0.5秒，小于5%的超调，和稳态误差小于1%。在部分水合条件下，在4-20%工程应变范围内，对直径在101-121 nm范围内的三种胶原原纤维进行蠕变和应力松弛测试。胶原纤维表现出非线性粘弹性行为，自适应准线性粘弹性模型很好地描述。这项研究的结果首次证明，哺乳动物胶原纤维，结缔组织的积木，在其部分水合状态下表现出非线性粘弹性行为。
Nanoscale macromolecular biological structures exhibit time-dependent mechanical behavior, yet a quantitative understanding of their creep and stress relaxation behavior remains elusive, largely due to experimental challenges in attaining sufficient spatial and temporal resolution and control of stress or strain in conditions that guarantee their molecular integrity. To address this gap, an experimental methodology was developed to conduct creep and stress relaxation experiments with individual mammalian collagen fibrils. An image-based edge detection method, implemented with high magnification optical microscopy and combined with closed-loop proportional–integral–derivative (PID) control, was implemented and calibrated to apply constant force or stretch ratio to individual collagen fibrils via a Microelectromechanical Systems (MEMS) device. This experimental methodology allowed for real-time control of uniaxial tensile stress or strain with ~25 nm displacement accuracy. The overall experimental system was tuned to apply step inputs with rise times below 0.5 s, less than 5% overshoot, and steady-state error smaller than 1%. Three collagen fibrils with diameters in the range 101–121 nm were subjected to creep and stress relaxation tests in the range 4–20% engineering strain, under partially hydrated conditions. The collagen fibrils demonstrated non-linear viscoelastic behavior that was described well by the adaptive quasi-linear viscoelastic model. The results of this study demonstrated for the first time that mammalian collagen fibrils, the building blocks of connective tissues, exhibit nonlinear viscoelastic behavior in their partially hydrated state.