Gravitaxis of asymmetric self-propelled colloidal particles
Gravitaxis of asymmetric self-propelled colloidal particles
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DOI：
10.1038/ncomms5829
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发表时间：
2014-09
影响因子：
16.6
通讯作者：
B. ten Hagen;F. Kümmel;R. Wittkowski;D. Takagi;H. Löwen;C. Bechinger
中科院分区：
文献类型：
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作者：
B. ten Hagen;F. Kümmel;R. Wittkowski;D. Takagi;H. Löwen;C. Bechinger
许多能动的微生物调整它们相对于重力场的游泳运动，从而抵消沉降到地面的作用。这种重力行为通常是不均匀质量分布的结果，这使得微生物类似于浮标。然而，也有人认为，重力轴也可能是由几何学上的前后不对称造成的，这是许多自我推进的生物体的典型特征。尽管有几次尝试，没有确凿的证据，这种不对称引起的引力运动存在。在这里，我们研究的运动的不对称自推进胶体粒子，具有均匀的质量密度和一个明确的形状。在实验和理论建模中，我们证明了形状各向异性本身就足以引起重力运动，无论是优先向上或向下游泳。此外，还观察到类似余摆线的轨迹横向于重力的方向。
Many motile microorganisms adjust their swimming motion relative to the gravitational field and thus counteract sedimentation to the ground. This gravitactic behaviour is often the result of an inhomogeneous mass distribution, which aligns the microorganism similar to a buoy. However, it has been suggested that gravitaxis can also result from a geometric fore–rear asymmetry, typical for many self-propelling organisms. Despite several attempts, no conclusive evidence for such an asymmetry-induced gravitactic motion exists. Here, we study the motion of asymmetric self-propelled colloidal particles which have a homogeneous mass density and a well-defined shape. In experiments and by theoretical modelling, we demonstrate that a shape anisotropy alone is sufficient to induce gravitactic motion with either preferential upward or downward swimming. In addition, also trochoid-like trajectories transversal to the direction of gravity are observed.