Spontaneous motion in hierarchically assembled active matter.
Spontaneous motion in hierarchically assembled active matter.
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层次组装的活动物质中的自发运动。
作者：
细胞凭借精湛的精度和可重复性，协调数千个纳米级分子马达的协作行动，以在更大的长度尺度上执行机械任务，例如细胞运动、分裂和复制。除了其生物学重要性之外，这种固有的非平衡过程还为利用消耗能量产生连续运动的微观成分开发仿生活性材料提供了灵感。在主动驱动下，这些材料不受平衡统计力学定律的约束，因此可以表现出备受追捧的特性，例如自主运动、内部产生的流动和自组织跳动。从可延伸的微管束开始，我们分层组装传统聚合物凝胶、液晶和乳液的活性类似物。在足够高的浓度下，微管形成一个渗透活性网络，其特征是内部驱动的混沌流、流体动力学不稳定性、增强的运输和流体混合。当限制在乳液液滴中时，3D 网络会自发吸附到液滴表面上，产生高活性的 2D 向列液晶，其流动受到内部产生的裂缝和自我修复以及带相反电荷的向错缺陷的释放和湮灭的控制。所得的活性乳液表现出意想不到的特性，例如自主运动，这是在其被动类似物中未观察到的。总而言之，这些观察结果说明了有生命的微观物体的组合如何表现出集体仿生特性，这些特性与无生命构件组装而成的材料中发现的特性截然不同，这对我们提出了挑战，要求我们开发一个理论框架，以便对其远离平衡的材料特性进行系统工程。
With exquisite precision and reproducibility, cells orchestrate the cooperative action of thousands of nanometer-sized molecular motors to carry out mechanical tasks at much larger length scales, such as cell motility, division and replication. Besides their biological importance, such inherently non-equilibrium processes are an inspiration for developing biomimetic active materials from microscopic components that consume energy to generate continuous motion. Being actively driven, these materials are not constrained by the laws of equilibrium statistical mechanics and can thus exhibit highly sought-after properties such as autonomous motility, internally generated flows and self-organized beating. Starting from extensile microtubule bundles, we hierarchically assemble active analogs of conventional polymer gels, liquid crystals and emulsions. At high enough concentration, microtubules form a percolating active network characterized by internally driven chaotic flows, hydrodynamic instabilities, enhanced transport and fluid mixing. When confined to emulsion droplets, 3D networks spontaneously adsorb onto the droplet surfaces to produce highly active 2D nematic liquid crystals whose streaming flows are controlled by internally generated fractures and self-healing, as well as unbinding and annihilation of oppositely charged disclination defects. The resulting active emulsions exhibit unexpected properties, such as autonomous motility, which are not observed in their passive analogues. Taken together, these observations exemplify how assemblages of animate microscopic objects exhibit collective biomimetic properties that are starkly different from those found in materials assembled from inanimate building blocks, challenging us to develop a theoretical framework that would allow for a systematic engineering of their far-from-equilibrium material properties.