School of Materials Science and Engineering , Harbin Institute of Technology (Shenzhen) , Shenzhen 518055 , China.
School of Physics and Astronomy and Institute of Natural Sciences , Shanghai Jiao Tong University , Shanghai 200240 , China.
Langmuir. 2018 Mar 13;34(10):3289-3295. doi: 10.1021/acs.langmuir.7b04301. Epub 2018 Feb 27.
Micromotors are an emerging class of micromachines that could find potential applications in biomedicine, environmental remediation, and microscale self-assembly. Understanding their propulsion mechanisms holds the key to their future development. This is especially true for a popular category of micromotors that are driven by asymmetric surface photochemical reactions. Many of these micromotors release ionic species and are propelled via a mechanism termed "ionic self-diffusiophoresis". However, exactly how it operates remains vague. To address this fundamental yet important issue, we have developed a dielectric-AgCl Janus micromotor that clearly moves away from the AgCl side when exposed to UV or strong visible light. Taking advantage of numerical simulations and acoustic levitation techniques, we have provided tentative explanations for its speed decay over time as well as its directionality. In addition, photoactive AgCl micromotors demonstrate interesting gravitactic behaviors that hint at three-dimensional transport or sensing applications. The current work presents a well-controlled and easily fabricated model system to understand chemically powered micromotors, highlighting the usefulness of acoustic levitation for studying active matter free from the effect of boundaries.
微马达是一类新兴的微型机器，在生物医学、环境修复和微尺度自组装方面具有潜在的应用。了解它们的推进机制是它们未来发展的关键。对于一类由不对称表面光化学反应驱动的流行微马达来说尤其如此。这些微马达中的许多会释放离子物种，并通过一种称为“离子自扩散泳”的机制来推进。然而，其具体的工作原理仍不清楚。为了解决这个基本而重要的问题，我们开发了一种介电-氯化银 Janus 微马达，当它暴露在紫外光或强可见光下时，它会明显地从氯化银一侧移动。利用数值模拟和声学悬浮技术，我们对其随时间的速度衰减以及方向性提供了初步解释。此外，光活性的 AgCl 微马达表现出有趣的重力趋性行为，暗示着三维传输或传感应用。目前的工作提出了一个易于控制和制造的模型系统，以了解化学动力微马达，突出了声学悬浮在研究不受边界影响的活性物质方面的有用性。
