Force Distributions in Biopolymer Networks

细胞内生物聚合物网络具有许多活细胞的基本功能。它们稳定了细胞的结构，通过形成分子马达的轨迹来促进定向运输，并使细胞能够运动。这些网络中的大多数都表现出高度非线性的机械响应，这在宏观尺度上已经得到了很好的研究；然而，关于单个细丝的特定属性和网络结构如何影响非线性，在实验上知之甚少。在这个项目中，将开发一种方法，在没有和有外部负载的情况下，同时可视化网络体系结构和通过网络的力分布。网络将使用最近开发的3D扫描探针显微镜进行成像，该显微镜基于使用小胶体颗粒作为传感器的光学镊子。由于粒子的大小明显小于网络的典型网格大小，因此它可以在网络中自由扩散。驱动粒子运动的热力提供了一个自然位置扫描器。粒子位置之后是一个纳米精度和兆赫带宽的3D位置传感器。从粒子的三维位置直方图中提取网络结构和力分布。这个项目将提供对生物聚合物网络如何从单个细丝的力学中获得高度非线性的力学特性以及这些网络如何分配力的实验洞察。该领域的研究人员将能够改进他们的模型和/或开发新的模型。拟议的活动产生的更广泛的影响将是开发一种新的显微技术，用于成像生物聚合物网络中的纳米结构和力分布。学生们将接受最近开发的3D扫描探针显微镜的培训。这些数据将对与健康相关的研究和新材料的工程具有重要意义。此外，该项目是在跨学科领域为本科生和研究生整合研究和教育的理想选择。

Intracellular biopolymer networks perform many essential functions for living cells. They stabilize the architecture of cells, facilitate directed transport by forming tracks for molecular motors, and enable cell motility. Most of these networks show a highly nonlinear mechanical response that is well studied on the macroscopic scale; however little is known experimentally about how specific properties of the individual filaments and the network architecture contribute to the nonlinearity. In this project a method will be developed for simultaneously visualizing the network architecture and the distribution of forces through the network, without and with an external load. Networks will be imaged with a recently developed 3D scanning probe microscope based on optical tweezers that use a small colloidal particle as a sensor. As the size of the particle is significantly smaller than the typical mesh size of the network, it can diffuse freely through the network. Thermal forces which drive the motion of the particle provide a natural position scanner. The particle position is followed by a 3D position sensor with nanometer precision and megahertz bandwidth. The network structure and force distribution are extracted from 3D position histograms of the particle. This project will provide experimental insight into how biopolymer networks obtain highly nonlinear mechanical properties from the mechanics of individual filaments and how these networks distribute forces. Researchers in the field will be able to refine their models and/or develop new ones. The broader impact resulting from the proposed activity will be the development of a novel microscopic technique for imaging the nanoscopic architecture and force distributions in biopolymer networks. Students will be trained in recently developed 3D scanning probe microscopy. The data will be important for health related research and engineering of novel materials. Additionally, the project is ideal for integrating research and education for undergraduate, and graduate students in an interdisciplinary field.