Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields
This journal is © The Royal Society of Chemistry. Dispersions of paramagnetic colloids can be manipulated with external magnetic fields to assemble structures via dipolar assembly and control transport via magnetophoresis. For fields held steady in time, the dispersion structure and dynamic properti...
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| Format: | Article |
| Language: | English |
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Royal Society of Chemistry (RSC)
2021
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| Online Access: | https://hdl.handle.net/1721.1/136383 |
| _version_ | 1826211782088196096 |
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| author | Sherman, Zachary M Pallone, Julia L Erb, Randall M Swan, James W |
| author_facet | Sherman, Zachary M Pallone, Julia L Erb, Randall M Swan, James W |
| author_sort | Sherman, Zachary M |
| collection | MIT |
| description | This journal is © The Royal Society of Chemistry. Dispersions of paramagnetic colloids can be manipulated with external magnetic fields to assemble structures via dipolar assembly and control transport via magnetophoresis. For fields held steady in time, the dispersion structure and dynamic properties are coupled. This coupling can be problematic when designing processes involving field-induced forces, as particle aggregation competes against and hinders particle transport. Time-varying fields drive dispersions out-of-equilibrium, allowing the structure and dynamics to be tuned independently. Rotating the magnetic field direction using two biaxial fields is a particularly effective mode of time-variation and has been used experimentally to enhance particle transport. Fundamental transport properties, like the diffusivity and magnetophoretic mobility, dictate dispersions' out-of-equilibrium responses to such time-varying fields, and are therefore crucial to understand to effectively design processes utilizing rotating fields. However, a systematic study of these dynamic quantities in rotating fields has not been performed. Here, we investigate the transport properties of dispersions of paramagnetic colloids in rotating magnetic fields using dynamic simulations. We find that self-diffusion of particles is enhanced in rotating fields compared to steady fields, and that the self-diffusivity in the plane of rotation reaches a maximum value at intermediate rotation frequencies that is larger than the Stokes-Einstein diffusivity of an isolated particle. We also show that, while the magnetophoretic velocity of particles through the bulk in a field gradient decreases with increasing rotation frequency, the enhanced in-plane diffusion allows for faster magnetophoretic transport through porous materials in rotating fields. We examine the effect of porous confinement on the transport properties in rotating fields and find enhanced diffusion at all pore sizes. The confined and bulk values of the transport properties are leveraged in simple models of magnetophoresis through tortuous porous media. |
| first_indexed | 2024-09-23T15:11:19Z |
| format | Article |
| id | mit-1721.1/136383 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T15:11:19Z |
| publishDate | 2021 |
| publisher | Royal Society of Chemistry (RSC) |
| record_format | dspace |
| spelling | mit-1721.1/1363832022-04-01T16:23:46Z Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields Sherman, Zachary M Pallone, Julia L Erb, Randall M Swan, James W This journal is © The Royal Society of Chemistry. Dispersions of paramagnetic colloids can be manipulated with external magnetic fields to assemble structures via dipolar assembly and control transport via magnetophoresis. For fields held steady in time, the dispersion structure and dynamic properties are coupled. This coupling can be problematic when designing processes involving field-induced forces, as particle aggregation competes against and hinders particle transport. Time-varying fields drive dispersions out-of-equilibrium, allowing the structure and dynamics to be tuned independently. Rotating the magnetic field direction using two biaxial fields is a particularly effective mode of time-variation and has been used experimentally to enhance particle transport. Fundamental transport properties, like the diffusivity and magnetophoretic mobility, dictate dispersions' out-of-equilibrium responses to such time-varying fields, and are therefore crucial to understand to effectively design processes utilizing rotating fields. However, a systematic study of these dynamic quantities in rotating fields has not been performed. Here, we investigate the transport properties of dispersions of paramagnetic colloids in rotating magnetic fields using dynamic simulations. We find that self-diffusion of particles is enhanced in rotating fields compared to steady fields, and that the self-diffusivity in the plane of rotation reaches a maximum value at intermediate rotation frequencies that is larger than the Stokes-Einstein diffusivity of an isolated particle. We also show that, while the magnetophoretic velocity of particles through the bulk in a field gradient decreases with increasing rotation frequency, the enhanced in-plane diffusion allows for faster magnetophoretic transport through porous materials in rotating fields. We examine the effect of porous confinement on the transport properties in rotating fields and find enhanced diffusion at all pore sizes. The confined and bulk values of the transport properties are leveraged in simple models of magnetophoresis through tortuous porous media. 2021-10-27T20:35:08Z 2021-10-27T20:35:08Z 2019 2019-09-12T17:45:38Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/136383 en 10.1039/c9sm00890j Soft Matter Creative Commons Attribution 3.0 unported license https://creativecommons.org/licenses/by/3.0/ application/pdf Royal Society of Chemistry (RSC) Royal Society of Chemistry (RSC) |
| spellingShingle | Sherman, Zachary M Pallone, Julia L Erb, Randall M Swan, James W Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| title | Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| title_full | Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| title_fullStr | Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| title_full_unstemmed | Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| title_short | Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| title_sort | enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields |
| url | https://hdl.handle.net/1721.1/136383 |
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