Evaporation-Induced Branched Structures from Sessile
Nanofluid Droplets
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Abstract
We
investigate the formation of branched nanoparticle aggregates
resulting from the evaporation of sessile nanofluid droplets of the
copper water-based nanofluids experimentally. Both symmetric and asymmetric
drying patterns were found as the sessile droplet evaporated. A kinetic
Monte Carlo (KMC) approach is developed to explain the drying process
in a circular domain, representing the top view of a drying sessile
droplet. It is found that the lattice-gas-based Monte Carlo model
can describe the nanoparticle self-assembly into a solid highly branched
aggregate. While the chemical potential function is coupled to the
nondimensional spherical droplet size during evaporation, the results
reveal that the fingering contact line instabilities can emerge under
a given condition and force the formation of a branched nanoparticle
structure. The pattern comparison shows that the simulation results
have a qualitative agreement with the experiments. The parameter study
shows that the model parameters, such as domain diameter, chemical
potential distribution, particle interaction energy, and so on, have
significant influence on the resulting patterns