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On the Convective Self-Assembly of Colloidal Particles in Nanofluid Based on in Situ Measurements of Interaction Forces
journal contribution
posted on 2019-08-23, 18:33 authored by Nozomi Arai, Satoshi Watanabe, Minoru T. MiyaharaWhile
the currently available techniques for the self-assembly
of colloidal particles show great promise owing to their simplicity
and high efficiency, they are plagued by the fact that they result
in colloidal crystals with defects. Here, in order to overcome this
problem, we propose a strategy that uses a suspension of nanoparticles
(i.e., a nanofluid) as the “solvent” for the colloidal
particles. We fabricated colloidal films of microspheres using such
a nanofluid suspension and performed in situ measurements of the interaction
forces between the microspheres in the nanofluid. This was done in
order to systematically elucidate the effects of the nanoparticle
size and the thickness of the electric double layer (Debye length)
on the self-assembly process. The obtained results confirm that the
use of the nanofluid results in a monolayer with a higher degree of
order than that in the case of films formed using pure water. Further,
the optimal size of the nanoparticles is determined based on the balance
between their physical size and the Debye length. We also show that
the lodging of the nanoparticles between the microspheres decreases
both the lubrication force and the friction force between them. Thus,
in this study, we show, for the first time, that a nanofluid can be
used in the self-assembly process for improving the regularity of
the fabricated colloidal particle arrays, as it inhibits the aggregation
of the particles and limits the lubrication and friction forces between
them.