Patchy Bubble‐Propelled Colloids at Interfaces
Patchy Bubble‐Propelled Colloids at Interfaces
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DOI：
10.1002/admi.202300226
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发表时间：
2023-08
影响因子：
5.4
通讯作者：
David P. Rivas;Max Sokolich;Harrison Muller;Sambeeta Das
中科院分区：
文献类型：
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作者：
David P. Rivas;Max Sokolich;Harrison Muller;Sambeeta Das
液-液或液-气界面为研究胶体提供了有趣的环境，在自然界和工业中普遍存在，在涉及乳液和泡沫的应用中也是如此。它们为研究主动粒子提供了一个特别有趣的环境，这些粒子展示了许多在被动系统中看不到的现象。活性粒子还可以提供按需控制，这大大扩展了它们在未来应用中的用途。然而，与固体表面或块体中的活性粒子相比，界面活性粒子的研究相对较少。在这里，介绍了在液体介质中，通过催化分解化学燃料而产生的气泡自推进的液-气界面上的磁控活性胶体。研究了表面有一块催化涂层的“片状”胶体的气泡形成和动力学，并与更传统的具有半球涂层的Janus胶体进行了比较。这种片状胶体倾向于产生更小的气泡并进行更平稳的运动，这使得它们有利于精确的微操作等应用。这是通过在衬底上以及在气液界面上操纵和组装被动球体的图案来演示的。对Janus胶体和片状胶体的推进和气泡形成进行了表征，发现以前提出的理论不足以全面描述它们的运动和气泡破裂机制。此外，位于气液界面的胶体显示出新的界面正重力轴朝向液滴边缘，这归因于胶体上相反的向下和浮力产生的扭矩。
Liquid–liquid or liquid–air interfaces provide interesting environments to study colloids and are ubiquitous in nature and industry, as well as relevant in applications involving emulsions and foams. They present a particularly intriguing environment for studying active particles which exhibit a host of phenomena not seen in passive systems. Active particles can also provide on‐demand controllability that greatly expands their use in future applications. However, research on active particles at interfaces is relatively rare compared to those at solid surfaces or in the bulk. Here, magnetically steerable active colloids at liquid–air interfaces that self‐propel by bubble production via the catalytic decomposition of chemical fuel in the liquid medium is presented. The bubble formation and dynamics of “patchy” colloids with a patch of catalytic coating on their surface is investigated and compared to more traditional Janus colloids with a hemispherical coating. The patchy colloids tend to produce smaller bubbles and undergo smoother motion which makes them beneficial for applications such as precise micro‐manipulation. This is demonstrated by manipulating and assembling patterns of passive spheres on a substrate as well as at an air–liquid interface. The propulsion and bubble formation of both the Janus and patchy colloids is characterized and it is found that previously proposed theories are insufficient to fully describe their motion and bubble bursting mechanism. Additionally, the colloids, which reside at the air–liquid interface, demonstrate novel interfacial positive gravitaxis towards the droplet edges which is attributed to a torque resulting from opposing downward and buoyant forces on the colloids.