Ferromagnetic liquid droplets with adjustable magnetic properties

Xuefei Wu; Robert Streubel; Xubo Liu; Paul Y Kim; Yu Chai; Qin Hu; Dong Wang; Peter Fischer; Thomas P Russell

doi:10.1073/pnas.2017355118

Ferromagnetic liquid droplets with adjustable magnetic properties

Proc Natl Acad Sci U S A. 2021 Feb 23;118(8):e2017355118. doi: 10.1073/pnas.2017355118.

Authors

Xuefei Wu^{1

2

3}, Robert Streubel^{4

5

6}, Xubo Liu^{1

2

3

7}, Paul Y Kim³, Yu Chai^{3

8

9}, Qin Hu^{3

10

11}, Dong Wang^{12

2}, Peter Fischer^{3

13}, Thomas P Russell^{12

3

10

14}

Affiliations

¹ Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
² State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China.
³ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
⁴ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; streubel@unl.edu dwang@mail.buct.edu.cn tom.p.russell@gmail.com.
⁵ Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588.
⁶ Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588.
⁷ CAS Key Laboratory of Bio-Inspired Materials and Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
⁸ Department of Physics, City University of Hong Kong, Kowloon, Hong Kong, China.
⁹ Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
¹⁰ Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, MA 01003.
¹¹ School of Microelectronics, University of Science and Technology of China, Hefei, Anhui 230026, China.
¹² Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China; streubel@unl.edu dwang@mail.buct.edu.cn tom.p.russell@gmail.com.
¹³ Physics Department, University of California, Santa Cruz, CA 95064.
¹⁴ World Premier Institute-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.

Abstract

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.

Keywords: 3D nanomagnetism; ferromagnetic liquid droplet; liquid–liquid interface; magnetic nanoparticle-surfactants; self-assembly.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.