We study the effect of inhomogeneous environments on the swimming direction of the microalgae Chlamydomonas reinhardtii (CR) in the presence of a light stimulus. Positive or negative phototaxis describe the ability of microorganisms to bias their swimming toward or away from a light source. Here we consider microswimmers with negative phototaxis in a microfluidic device with a microfabricated square lattice of pillars as obstacles. We measured a mean deflection of microswimmers that shows an interesting nonlinear dependence on the direction of the guiding light beam with respect to the symmetry axes of the pillar lattice. By simulating a model swimmer in a pillar lattice and analyzing its scattering behavior, we identified the width of the reorientation distribution of swimmers to be also crucial for the nonlinear behavior of the swimmer deflection. On the basis of these results we suggest in addition an analytical model for microswimmers, where the pillar lattice is replaced by an anisotropic scattering medium, that depends only on a scattering rate and the width of the reorientation distribution of swimmers. This flexible and handy model fits the experimental results as well. The presented analysis of the deflection of light guided swimmers through pillar lattice may be used for separating swimmers having different reorientation distributions.

中文翻译：

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通过障碍物阵列偏转光战术微泳者

我们研究了不均匀环境对微藻衣藻（Chlamydomonas reinhardtii）游动方向的影响（CR）在有轻微刺激的情况下。正趋光性或负趋光性描述了微生物偏向或远离光源游动的能力。在这里，我们将微流控设备中具有趋光性为负的微游泳器与微细制造的立柱方阵作为障碍物。我们测量了微游泳者的平均偏转，该偏转显示出与引导光束的方向有关的相对于柱格对称轴的有趣非线性关系。通过在柱状格子中模拟模型游泳者并分析其散射行为，我们确定了游泳者重新定向分布的宽度对于游泳者挠曲的非线性行为也至关重要。根据这些结果，我们建议另外使用微游泳者的分析模型，柱状晶格被各向异性的散射介质代替，该各向异性的散射介质仅取决于散射速率和游泳者重新定向分布的宽度。这种灵活方便的模型也符合实验结果。所提出的光导游泳者通过柱格的偏转的分析可以用于分离具有不同取向分布的游泳者。