Collaborative Research: Multiscale Study of Active Cellular Matter: Simulation, Modeling, and Analysis

活性细胞物质是由悬浮细胞骨架细丝和分子马达混合而成的新型合成活性液体的基础。通过消耗化学燃料，分子马达（如动力蛋白）可以结合并在生物丝（如微管）之间产生主动移动的交联，以驱动它们的相对运动，从而通过流体动力耦合导致丝/马达混合物中的大规模集体运动。由少量成分组成的合成主动悬架揭示了在活细胞中组装和组织的高阶方面是如何构建的。这些系统也对我们对材料的理解、设计和分析提出了新的挑战，并有可能提供有价值的新技术，如自主移动和自愈材料。在这项工作中，研究者通过多尺度方法，以及紧密耦合的建模、分析和模拟，研究了由微管和分子马达组成的活性细胞物质。该项目旨在了解动态不稳定的刚性/柔性生物丝束内应力产生的基本相互作用，以及大规模集体运动中的非线性动力学和分层模式形成。该项目还将预测关键的材料特性，包括其相干结构、局部非均质性、时间和长度尺度以及材料流变学。为了在不同的长度和时间尺度上解决物理问题，将开发和集成几种方法：(1)将使用动力学蒙特卡罗方法模拟微管-电机相互作用；(2)采用非局部细长体/边界积分法和快速求和法对不同形状物体间的水动力相互作用进行建模；(3)采用伪谱法通过连续主动液晶型模型模拟集体运动。

Active cellular matter is the basis of novel synthetic active fluids made of mixtures of suspended cytoskeletal filaments and molecular motors. By consuming chemical fuel, the molecular motors (e.g., kinesins) can bind to and create actively moving crosslinks between the biofilaments (e.g., microtubules) to drive their relative motion, which leads to large-scale collective motions in the filament/motor mixture through hydrodynamic coupling. Synthetic active suspensions made of small numbers of components reveal how higher-order aspects of assembly and organization are built in living cells. These systems also present new challenges to our understanding, design, and analysis of materials, and have the potential to provide valuable new technologies such as autonomously moving and self-healing materials.In this work, the investigators study active cellular matter composed of microtubules and molecular motors through multiscale methods, and tightly coupled modeling, analysis, and simulation. The project aims to understand the fundamental interactions underlying stress generation within bundles of rigid/flexible biofilaments that undergo dynamic instability, as well as the nonlinear dynamics and hierarchical pattern formation in large-scale collective motions. The project will also predict key material properties including its coherent structures, local heterogeneity, time- and length-scales, and material rheology. To resolve the physics at different length- and time-scales, several methods will be developed and integrated: (1) microtubule-motor interactions will be simulated using a kinetic Monte Carlo method; (2) the hydrodynamic interactions between objects of various shapes will be modeled using a nonlocal slender body/boundary integral method, together with fast summation methods; (3) a pseudo-spectral method will be implemented to simulate the collective motion through a continuous active liquid-crystal type model.