Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Biophys J. 2010 Apr 21;98(8):1632-40. doi: 10.1016/j.bpj.2009.12.4312.
As the structural backbone of blood clots, fibrin networks carry out the mechanical task of stemming blood flow at sites of vascular injury. These networks exhibit a rich set of remarkable mechanical properties, but a detailed picture relating the microscopic mechanics of the individual fibers to the overall network properties has not been fully developed. In particular, how the high strain and failure characteristics of single fibers affect the overall strength of the network is not known. Using a combined fluorescence/atomic force microscope nanomanipulation system, we stretched 2-D fibrin networks to the point of failure, while recording the strain of individual fibers. Our results were compared to a pair of model networks: one composed of linearly responding elements and a second of nonlinear, strain-stiffening elements. We find that strain-stiffening of the individual fibers is necessary to explain the pattern of strain propagation throughout the network that we observe in our experiments. Fiber strain-stiffening acts to distribute strain more equitably within the network, reduce strain maxima, and increase network strength. Along with its physiological implications, a detailed understanding of this strengthening mechanism may lead to new design strategies for engineered polymeric materials.
作为血栓的结构骨干，纤维蛋白网络执行着阻止血管损伤部位血流的机械任务。这些网络表现出一系列丰富的显著机械性能，但将单个纤维的微观力学与整体网络特性联系起来的详细情况尚未完全阐明。特别是，单根纤维的高应变和失效特性如何影响网络的整体强度尚不清楚。使用荧光/原子力显微镜纳米操纵系统，我们将 2-D 纤维蛋白网络拉伸至失效点，同时记录单个纤维的应变。我们的结果与一对模型网络进行了比较：一个由线性响应元件组成，另一个由非线性、应变硬化元件组成。我们发现，单个纤维的应变硬化对于解释我们在实验中观察到的网络中应变传播模式是必要的。纤维应变硬化的作用是在网络内更均匀地分布应变，降低应变最大值，并提高网络强度。除了其生理意义外，对这种强化机制的详细了解可能会为工程聚合物材料的新设计策略提供依据。
