Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China.
Proc Natl Acad Sci U S A. 2021 Feb 23;118(8). doi: 10.1073/pnas.2017355118.
The assembly and jamming of magnetic nanoparticles (NPs) at liquid-liquid interfaces is a versatile platform to endow structured liquid droplets with a magnetization, i.e., producing ferromagnetic liquid droplets (FMLDs). Here, we use hydrodynamics experiments to probe how the magnetization of FMLDs and their response to external stimuli can be tuned by chemical, structural, and magnetic means. The remanent magnetization stems from magnetic NPs jammed at the liquid-liquid interface and dispersed NPs magneto-statically coupled to the interface. FMLDs form even at low concentrations of magnetic NPs when mixing nonmagnetic and magnetic NPs, since the underlying magnetic dipole-driven clustering of magnetic NP-surfactants at the interface produces local magnetic properties, similar to those found with pure magnetic NP solutions. While the net magnetization is smaller, such a clustering of NPs may enable structured liquids with heterogeneous surfaces.
在液-液界面上组装和阻塞磁性纳米颗粒 (NPs) 是赋予结构化液滴磁化的多功能平台，即产生铁磁液滴 (FMLD)。在这里，我们使用流体动力学实验来探测 FMLD 的磁化及其对外界刺激的响应如何通过化学、结构和磁学手段进行调节。剩余磁化源于被阻塞在液-液界面上的磁性 NPs 和与界面磁静电耦合的分散 NPs。当混合非磁性和磁性 NPs 时，即使在磁性 NPs 的低浓度下也会形成 FMLD，因为界面上磁性 NP-表面活性剂的磁偶极子驱动的聚类会产生类似于纯磁性 NP 溶液中的局部磁特性。虽然净磁化强度较小，但这种 NPs 聚类可能会使具有异质表面的结构化液体成为可能。
