由许蕾蕾、马冲等撰写的研究论文“NIR light-steered magnetic liquid marbles with switchable positive/negative phototaxis”被Elsiever工程技术一区top期刊Applied Materials Today接收。在该论文中，我们用油酸修饰的Fe3O4纳米颗粒(Fe3O4@ OA NPs)封装水滴制备演示了一种具有可切换正/负趋光性和优异机械稳定性的磁性液体弹珠。这种磁性液体弹珠的高度可达4.7 mm，有效表面张力约为54 mN m-1。由于采用的疏水性Fe3O4@OA NPs具有的光热效应和超顺磁特性，我们可以通过近红外光和磁场能有效操控这种磁性液体弹珠在水面上的运动。它的光操纵运动源于光热效应引起的马朗戈尼流，其运动速度可以用近红外光的入射角和光强控制。更有趣的是，由于Fe3O4@OA NPs具有独特的光吸收/透射特性，这会使得这种磁性液体弹珠可以通过简单地改变光照射位置，运动方向可从趋近近红外光源转变为远离近红外光源，即表现为从正趋光性转化为负趋光性。这与先前报道的光驱动活性物质只表现出单一趋光性有显著的不同。这一发现为磁液体弹珠的远程操控提供了一种先进的策略，有利于其在化学和生物领域的微尺度应用的开发，也能为活性物质的趋光性调控提供一种新方法。
原文摘要如下：This work has demonstrated a magnetic liquid marble of switchable positive/negative phototaxis and excellent mechanical stability by encapsulating water droplet with oleic acid modified Fe3O4 nanoparticles (Fe3O4@OA NPs). The as-constructed marble can reach a height up to 4.7 mm, indicating an effective surface tension of ~54 mN m-1. The marble on water surface can be steered by NIR light as well as magnetic field due to the photothermal effect and superparamagnetic feature of the Fe3O4@OA NPs. Its light-steered motion stems from the photothermal effect-induced Marangoni flow with speed controlled by the incident angles and light intensities. More interestingly, the marble can alter the motion direction from toward (positive phototaxis) to away from (negative phototaxis) NIR light source by simply changing the light irradiation position from upper to lower semi-marbles due to the unique light absorbance/transmittance characteristics of the Fe3O4@OA NPs. This is dramatically different from previously reported light-driven active matters that only show single phototaxis. This finding provides an advanced strategy to remotely steer magnetic liquid marbles, which may stimulate the exploitation of their application in chemistry and biology fields at microscale, and enlightens a method for phototactic regulation of active matters.
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