Department of Physics, Brandeis University, 415 South Street, Waltham, MA 02453, USA.
School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30339, USA.
Science. 2017 Mar 24;355(6331). doi: 10.1126/science.aal1979.
Transport of fluid through a pipe is essential for the operation of macroscale machines and microfluidic devices. Conventional fluids only flow in response to external pressure. We demonstrate that an active isotropic fluid, composed of microtubules and molecular motors, autonomously flows through meter-long three-dimensional channels. We establish control over the magnitude, velocity profile, and direction of the self-organized flows and correlate these to the structure of the extensile microtubule bundles. The inherently three-dimensional transition from bulk-turbulent to confined-coherent flows occurs concomitantly with a transition in the bundle orientational order near the surface and is controlled by a scale-invariant criterion related to the channel profile. The nonequilibrium transition of confined isotropic active fluids can be used to engineer self-organized soft machines.
在宏观机器和微流控设备的运行中，流体在管道中的输送是必不可少的。传统的流体仅在响应外部压力时才流动。我们证明了由微管和分子马达组成的各向同性主动流体可以自主地流过长达一米的三维通道。我们可以控制自组织流的大小、速度分布和方向，并将其与延伸微管束的结构相关联。在从整体湍流到受限相干流的固有三维转变过程中，表面附近的束取向有序发生转变，这由与通道轮廓相关的标度不变判据控制。受限各向同性主动流体的非平衡转变可用于设计自组织软机器。
