Surface nano-patterning using the coffee-stain effect
dc.contributor.advisor
Sefiane, Khellil
en
dc.contributor.advisor
Koutsos, Vasileios
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dc.contributor.author
Askounis, Alexandros
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dc.contributor.sponsor
other
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dc.date.accessioned
2015-06-22T10:08:50Z
dc.date.available
2015-06-22T10:08:50Z
dc.date.issued
2015-06-29
dc.description.abstract
Addition of nanopacticles in a base solvent leads to suspensions with enhanced physiochemical
properties, compared to base solvent. This new type of suspensions is called
nanofluids, with applications ranging from biomedicine to automotives. As a
consequence extensive research is being conducted in the field, in particular, on the
evaporation of these fluids as it leads to well-defined and highly ordered coffee-rings.
However, the exact physics governing this phenomenon remain elusive. The goal of
this experimental investigation is to elucidate how various parameters affect the
progression of nanofluid coffee-stain formation.
Examination of the coffee-ring structuring, produced by the free evaporation of sessile
droplets containing nanoparticles, revealed an unexpected, disordered region at the
exterior edge of the ring. A self-assembly mechanism with two components, particle
velocity and wedge constraints, was proposed to describe the deposition of particles at
contact lines of evaporating drops.
Environmental pressure was used as a method to control particle crystallinity in the
coffee-rings. Essentially, evaporation rate and pressure were found to be inversely
proportional. Macroscopically, lowering pressure led to a transition from “stick-slip”
to constant pinning. Nanoscopically, lowering pressure promoted crystallinity.
Findings supported the proposed, in this thesis, particle self-assembly mechanism.
Particle aspect ratio and flexibility were subsequently examined. Pinning strength was
found to be a function of particle aspect ratio and rigidity, leading to constant pinning.
The proposed, in this thesis, particle self-assembly mechanism was found to be
applicable to a variety of aspect ratios and flexibilities. Lastly, particulate crystals grew
following different pathways depending on particle flexibility.
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dc.identifier.uri
http://hdl.handle.net/1842/10450
dc.language.iso
en
dc.publisher
The University of Edinburgh
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dc.relation.hasversion
Askounis A, Sefiane K, Koutsos V, Shanahan MER, Effect of particle geometry on triple line motion of nano-fluid drops and deposit nano-structuring. Advances in Colloid and Interface Science,
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dc.relation.hasversion
Askounis A, Sefiane K, Koutsos V, Shanahan MER. The effect of evaporation kinetics on nanoparticle structuring within contact line deposits of volatile drops. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014, 441, 855-866.
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dc.relation.hasversion
Askounis A, Sefiane K, Koutsos V, Shanahan MER. Structural transitions in a ring stain created at the contact line of evaporating nanosuspension sessile drops. Physical Review E, 2013, 87, 012301.
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dc.relation.hasversion
Askounis, A., et al., Structural transitions in a ring stain created at the contact line of evaporating nanosuspension sessile drops. Physical Review E, 2013. 87(1): p. 012301-1-8.
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dc.relation.hasversion
Askounis, A., et al., Nanoparticle deposits near the contact line of pinned volatile droplets: size and shape revealed by atomic force microscopy. Soft Matter, 2011. 7(9): p. 4152-4155.
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dc.subject
AFM
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dc.subject
droplet evaporation
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dc.subject
coffee-stain
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dc.subject
nanostructures
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dc.subject
colloids
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dc.title
Surface nano-patterning using the coffee-stain effect
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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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