Sessile droplet evaporation on patterned surfaces
In this study, the evaporation behaviour between suspension fluids and water droplets has been investigated on different substrates. The sizes of particles in the suspension fluids increases by a factor of ten sizes from 0.05μm, 0.5μm and 6μm. The substrates used are Al2O3, TiO2 flat and a patter...
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Format: | Final Year Project |
Language: | English |
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Nanyang Technological University
2023
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Online Access: | https://hdl.handle.net/10356/167269 |
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Institution: | Nanyang Technological University |
Language: | English |
Summary: | In this study, the evaporation behaviour between suspension fluids and water droplets
has been investigated on different substrates. The sizes of particles in the suspension
fluids increases by a factor of ten sizes from 0.05μm, 0.5μm and 6μm. The substrates
used are Al2O3, TiO2 flat and a patterned micro pyramid substrate. For the patterned
substrate, a 0º and 45º line of sights are used. Both offer different properties such as
hydrophobicity. As such, the interaction and behaviour of the fluid are experimented
with using a combination of microscopy and a high-speed camera. Specifically, the
dimensions and contact angles of the droplets are taken throughout the evaporation
phase. Thereafter, a surface roughness profile is developed to detail the exact
deposition using a confocal microscopy. First, DI water droplets provide a good base
line for the substrate properties and a comparator for the suspension fluid droplets. The
results show the substrates differs in hydrophobicity. However, fluid with colloidal
particles overall increases the contact angle and decreases the dimensions of the
contact line which gave an overall increase in hydrophobicity. For the patterned
substrate at Ls0º, it increases further in hydrophobicity as the micro pyramid structures
acts as barrier. This is different at Ls45º where it was not as hydrophobic as Ls0º.
There were inherent directional properties of the micro pyramid substrate which
correlates to the wetting properties. Furthermore, the observation of the final dried
deposited pattern was that the outward capillary flow becomes less dominant as the
particle sizes increases. With a bigger particle size, the coffee-ring pattern becomes
less dominant which slowly transitions into a uniform pattern. This study provides
important insights into the mechanisms of how suspension fluids in the same
concentration behaves in the presence of different substrates with different properties. |
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