The synthesis, characterisation, and analysis of Janus photocatalytic microswimmers (Does active matter?)
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Author
Date
2023Type
- Doctoral Thesis
ETH Bibliography
yes
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Abstract
In this thesis, we investigate the ability of synthetic micron-scale spherical particles to induce localised fluid mixing in solutions. In particular, we study the mixing properties of a newly developed photo-responsive Janus microswimmer system, which we fabricate via the asymmetric functionalisation of SiO2 microparticle supports with photocatalytic nanoparticles using Pickering emulsions. We begin our investigation by developing the synthetic platform which we use to obtain the multi-responsive Janus microswimmers. We demonstrate that our fabrication technique preserves the functional properties of the nanoparticles, suggesting alternative routes for the support of these nano-materials. The 3-D physics of our synthesised microswimmers is then characterised with the aid of machine-learning algorithms. Specifically, we demonstrate that traditional machine-learning models can outperform deep-learning algorithms with appropriate image analysis. The extracted trajectories are then utilised to guide numerical simulations of our Janus particle motion, using a dissipative-particle-dynamics framework implemented on the Large-scale Atomic/Molecular Massively Parallel Simulator. We find that out-of-plane dynamics of the microswimmers is attributable to the presence of asperities on their surface, arising from the use of nanoparticles to functionalise our micoparticles. We conclude by probing the mixing properties of our microswimmer suspensions using tracer particles and numerical simulations. We find good agreement between the squirmer model and our experimental findings, which demonstrate a general inability for such microswimmer systems to mix suspensions, given the current state-of-the-art and length-scales of interest. Our findings therefore identify key limitations with the “chemistry-on-the-fly" concept, as well as more promising avenues of research into microswimmers acting as “micro-stirrers". Show more
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https://doi.org/10.3929/ethz-b-000650952Publication status
publishedExternal links
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Publisher
ETH ZurichSubject
Active matter; Janus particlesOrganisational unit
09455 - Isa, Lucio / Isa, Lucio
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ETH Bibliography
yes
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