Abstract
A homogeneous magnetic field can exert no net force on a colloidal particle. However, by coupling the particle's orientation to its position on a curved interface, even static homogeneous fields can be used to drive rapid particle motions. Here, we demonstrate this effect using magnetic Janus particles with amphiphilic surface chemistry adsorbed at the spherical interface of a water drop in decane. Application of a static homogeneous field drives particle motion to the drop equator where the particle's magnetic moment can align parallel to the field. As explained quantitatively by a simple model, the effective magnetic force on the particle scales linearly with the curvature of the interface. For particles adsorbed on small droplets such as those found in emulsions, these magneto-capillary forces can far exceed those due to magnetic field gradients in both magnitude and range. This mechanism may be useful in creating highly responsive emulsions and foams stabilized by magnetic particles.
Original language | English (US) |
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Pages (from-to) | 4661-4665 |
Number of pages | 5 |
Journal | Soft Matter |
Volume | 14 |
Issue number | 23 |
DOIs | |
State | Published - 2018 |
Funding
This work was supported as part of the Center for Bio-Inspired Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0000989. M. M. D. was supported by the Gordon and Betty Moore Foundation through Grant GBMF3849.
ASJC Scopus subject areas
- General Chemistry
- Condensed Matter Physics