Shaping drops with magnetic fields
dc.contributor.advisor
Stokes, Adam
en
dc.contributor.advisor
Terry, Jonathan
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dc.contributor.advisor
Smith, Stewart
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dc.contributor.author
Dodoo, Jennifer
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dc.contributor.sponsor
Engineering and Physical Sciences Research Council (EPSRC)
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dc.date.accessioned
2020-01-30T12:18:12Z
dc.date.available
2020-01-30T12:18:12Z
dc.date.issued
2020-01-23
dc.description.abstract
The control of small volumes of fluids (or drops) is important for a wide range of
applications, including lab-on-chip devices, where drops are transported and merged
for sensing and chemical mixing; liquid lenses, where drops are shaped to set optical
properties; and printing, where drops are generated by nozzles. Electric techniques
are widely used to generate, transport, split and merge drops. Equivalent magnetic
techniques are less well-known. Similarly to electric dipoles in electric fields, magnetic
dipoles experience a force in magnetic fields. This effect, called magnetophoresis,
is used to shape ferrofluids in magnetic valves and seals. Interest in shaping
drops with magnetic fields for microfluidics has recently increased, and ferrofluids
and paramagnetic salt solutions have been studied. The rich phenomenology of the
interaction of magnetic fields and fluids offers ample opportunities for exploration.
Diamagnetic fluids for example have no natural electric equivalent and are rarely
studied as a tool for microfluidics.
In this thesis, I study the shaping of drops with magnetic fields. My research focus
is on para- and diamagnetic salt solutions. Deformation of drops using external fields
and induced magnetism has not been fully explored in the literature. I study here
how induced magnetism can shape the liquid-vapour interface of drops and control
solids that float on them. This thesis includes (i) an introduction to the background
of the interaction of electromagnetic fields and fluids; (ii) a derivation of an expression
for the shape of drops in electromagnetic fields; (iii) experimental validation of
this expression through the measurement of the shape of para- and diamagnetic axisymmetric
sessile drops in homogeneous magnetic fields; (iv) demonstration of the
transport of para- and diamagnetic drops in magnetic field gradients; (v) explorations
of the use of shaping drops with magnetic fields for rheological measurements, and
for the controlled driving of objects floating on drops.
In summary, I explore how drops can be shaped in homogeneous magnetic fields,
and how the drops can be transported by magnetic field gradients. These fundamental
investigations may help stimulate novel applications of the controlled shaping of
drops with magnetic fields. In particular, I explore how this technique can be used in
rheology for food or medical research.
en
dc.identifier.uri
https://hdl.handle.net/1842/36708
dc.identifier.uri
http://dx.doi.org/10.7488/era/15
dc.language.iso
en
dc.publisher
The University of Edinburgh
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dc.relation.hasversion
Jennifer Dodoo and Adam A. Stokes, Shaping and transporting diamagnetic sessile drops, Biomicrofluidics, vol. 13, pp. 064110-1-064110-6, 2019.
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dc.relation.hasversion
Jennifer Dodoo, Glen McHale, and Adam A. Stokes, Shaping of sessile magnetic dropsdueto electromagnetic stress; arXiv:1908.05193.
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dc.subject
drop shapes
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dc.subject
diamagnetic drops
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dc.subject
paramagnetic drops
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dc.subject
magnetic fields
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dc.title
Shaping drops with magnetic fields
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dc.type
Thesis or Dissertation
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dc.type.qualificationlevel
Doctoral
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dc.type.qualificationname
PhD Doctor of Philosophy
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