Dynamics and thermodynamics of air-driven active spinners†,Soft Matter

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Dynamics and thermodynamics of air-driven active spinners†
Soft Matter ( IF 2.9 ) Pub Date : 2018-05-24 00:00:00 , DOI: 10.1039/c8sm00403j
Somayeh Farhadi _{1,

2,

3} , Sergio Machaca _{1,

2,

2,

3,

4} , Justin Aird _{1,

2,

3,

5,

6} , Bryan O. Torres Maldonado _{1,

2,

3,

7,

8} , Stanley Davis _{1,

2,

3,

9,

10} , Paulo E. Arratia _{1,

2,

3} , Douglas J. Durian _{1,

2,

3}

Affiliation

We report on the collective behavior of active particles in which energy is continuously supplied to rotational degrees of freedom. The active spinners are 3D-printed disks, 1 cm in diameter, that have an embedded fan-like structure, such that a sub-levitating up-flow of air forces them to spin. Single spinners exhibit Brownian motion with a narrow Gaussian velocity distribution function, P(v), for translational motion. We study the evolution of P(v) as the packing fraction and the average single particle spin speeds are varied. The interparticle hydrodynamic interaction is negligible, and the dynamics is dominated by hyperelastic collisions and dissipative forces. As expected for nonequilibrium systems, P(v) for a collection of many spinners deviates from Gaussian behavior. However, unlike translationally active systems, phase separation is not observed, and the system remains spatially homogeneous. We then search for a near-equilibrium counterpart for our active spinners by measuring the equation of state. Interestingly, it agrees well with a hard-sphere model, despite the dissipative nature of the single particle dynamics.

中文翻译：

气动主动微调器的动力学和热力学†

我们报告了活性粒子的集体行为，在这些行为中，能量不断提供给旋转自由度。活跃的微调器是直径为1 cm的3D打印磁盘，具有嵌入式扇形结构，因此空气的子悬浮上升会迫使它们旋转。单旋转器表现出布朗运动，该布朗运动具有较窄的高斯速度分布函数P（v），用于平移运动。我们研究了P（v）随堆积率的变化以及平均单粒子自旋速度的变化。粒子间的流体动力相互作用可忽略不计，而动力学主要由超弹性碰撞和耗散力决定。如非平衡系统所期望的那样，P（v），因为许多微调器偏离了高斯行为。但是，与平移系统不同，没有观察到相分离，并且该系统在空间上保持同质。然后，我们通过测量状态方程来为主动旋转器寻找接近平衡的对应物。有趣的是，尽管单个粒子动力学具有耗散性，但它与硬球模型非常吻合。

更新日期：2018-05-24

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