Manipulating Dispersions of Magnetic Nanoparticles

Abstract

Dispersions of magnetic nanoparticles (MNPs) can exhibit paramagnetic ferrofluid or ferromagnetic liquid behavior. By modifying the surface functionality of MNPs, ferrofluids have been used to fabricate novel magnetically actuated devices. If the surfacefunctionalized MNPs interact with complementary ligands at a fluid−fluid interface, MNP surfactants form and in situ assemble at the interface. When jammed interfacially, MNP surfactants give rise to ferromagnetic behavior of the liquid (droplet), which is endowed with permanent magnetic dipoles while maintaining all of the characteristics of a fluid system. Here, we give a brief overview of the developments in the dispersion of MNPs in liquids from ferrofluids to ferromagnetic liquid droplets, their responses to external fields, and the manipulation of these responses for end uses. The reversible room-temperature para-to-ferro transformation of magnetic liquids is highlighted. We discuss challenges in the synthesis and characterization of these unusual liquids along with potential technological applications.

High-Resolution Micro-object Separation by Rotating Magnetic Chromatography

“…The core of the RMC is the MFSC, where the mobile phase flows through a well-dosed amount of magnetic nanoparticles chemically modified with carboxyl groups to avoid self-aggregation phenomena. In the Supporting Information, a mathematical simulation of the rotating magnetic field and the separation principle is presented and discussed. − …”

Ferrofluids and bio-ferrofluids: looking back and stepping forward

“…801,803–805 Magnetowetting, a new feature specific to ferrofluid droplets 806 and ferrofluid thin films, 807 could provide an efficient way to manipulate magnetic or non-magnetic droplets for digital microfluidics and lab-on-a-chip applications. 593,663,710,742,805,806,808–810…”

“…Initially developed for space applications, ferrofluids proved to be today an essential component of a very large number of high-tech devices and processes. 161,[661][662][663] Ferrofluids are fully involved in nanotechnology contributions to industrial progress and environmental protection and to the overall improve-ment of everyone's quality of life. Tiny quantities of specially designed and manufactured ferrofluids produced a real revolution in leakage-free rotating seal technology and high-fidelity audio engineering.…”

“…801,[803][804][805] Magnetowetting, a new feature specific to ferrofluid droplets 806 and ferrofluid thin films, 807 could provide an efficient way to manipulate magnetic or non-magnetic droplets for digital microfluidics and lab-on-a-chip applications. 593,663,710,742,805,806,[808][809][810] 5.5.1 Ferrofluid droplet generation and control. Ferrofluid droplets of predetermined size, magnetic response and frequency are essential ingredients for magnetic microfluidics applications.…”

Superparamagnetic-blocked state transition under alternating magnetic fields: towards determining the magnetic anisotropy in magnetic suspensions

“…Recent progress in materials science has allowed the tuning of the magnetic behaviour of nanomaterials by controlling their size, shape, chemical composition and/or crystallinity. [1][2][3][4][5] Indeed, the bespoken design and synthesis of magnetic nanoparticles has led to the observation and understanding of customized magnetic phenomena. 6 This is the case of superparamagnetism, a magnetic behaviour related to nanoscale-sized materials with ferro-or ferrimagnetic order.…”