Photogravitactic Microswimmers
Photogravitactic Microswimmers
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DOI：
10.1002/adfm.201706660
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发表时间：
2018-06-20
影响因子：
19
通讯作者：
Fischer, Peer
中科院分区：
文献类型：
--
作者：
Singh, Dhruv P.;Uspal, William E.;Fischer, Peer
通常观察到，趋光微生物对自然阳光的反应是向上游动，不受重力的影响。这项研究表明，合成光化学活性微游泳者也可以在重力下游泳。颗粒最初沉淀，当在低光强度下照射时，在底部表面附近表现出壁面运动状态。在增加光的强度后，人造游泳者从墙上升起，对抗重力游泳，远离光源。这种整体运动已被全息显微镜进一步证实。在自扩散泳动的框架内提出了一个理论模型，它可以明确地确定光化学活性和光致反应作为观察到的现象的关键机制。由于起跳阈值强度取决于颗粒大小，因此可以利用它来选择性地从多分散的活性颗粒混合物中定位具有相同密度的颗粒，并将它们移进或移出边界区域。本研究提供了一种简单的设计策略来制造人工微游泳者，其二维或三维游泳行为可以用光来控制。
Phototactic microorganisms are commonly observed to respond to natural sunlight by swimming upward against gravity. This study demonstrates that synthetic photochemically active microswimmers can also swim against gravity. The particles initially sediment and, when illuminated at low light intensities exhibit wall-bound states of motion near the bottom surface. Upon increasing the intensity of light, the artificial swimmers lift off from the wall and swim against gravity and away from the light source. This motion in the bulk has been further confirmed using holographic microscopy. A theoretical model is presented within the framework of self-diffusiophoresis, which allows to unequivocally identify the photochemical activity and the phototactic response as key mechanisms in the observed phenomenology. Since the lift-off threshold intensity depends on the particle size, it can be exploited to selectively address particles with the same density from a polydisperse mixture of active particles and move them in or out of the boundary region. This study provides a simple design strategy to fabricate artificial microswimmers whose two- or three-dimensional swimming behavior can be controlled with light.