Swarming behavior of simple model squirmers

By S. Thutupalli, R. Seemann, Stephan Herminghaus. 2011

365 citations recorded by the source corpus.

We have studied experimentally the collective behavior of self-propelling liquid droplets, which closely mimic the locomotion of some protozoal organisms, the so-called squirmers. For the sake of simplicity, we concentrate on quasi-two-dimensional (2D) settings, although our swimmers provide a fully 3D propulsion scheme. At an areal density of 0.46, we find strong polar correlation of the locomotion velocities of neighboring droplets, which decays over less than one droplet diameter. When the areal density is increased to 0.78, distinct peaks show up in the angular correlation function, which point to the formation of ordered rafts. This shows that pronounced textures, beyond what has been seen in simulations so far, may show up in crowds of simple model squirmers, despite the simplicity of their (purely physical) mutual interaction.

Subfields: Biomedical Engineering, Condensed Matter Physics, Genetics

View Paper: https://www.semanticscholar.org/paper/4048c6e44040aacf7cb5a0d2e4747bc7a448d0cb

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Citations in the corpus

Self-Propulsion of Chemically Active Droplets (2022, methodology): “…motion (no bromine, Izri et al. 2014, Suematsu et al. 2021); (ii) fast and reorienting propulsion (fixed supply or steady bromine production, Thutupalli et al. 2011, Suematsu et al. 2019); (iii) retarded transition between these regimes (Suematsu et al. 2021); or (iv) large amplitude…”
Microswimming in viscoelastic fluids (2021, background): “A squirmer is also the appropriate mathematical model to describe the motion of a self-propelled droplet driven by marangoni stresses [103,104] and autophoretic colloidal particles driven by electrophoresis, diffusiophoresis or thermophoresis, be they externally driven or self-generated [29,105,106]”
Spherical squirmers: models for swimming micro-organisms (2016, methodology): “The two-dimensional results receive qualitative support from the experiments of Thutupalli et al. (2011), using synthetic squirmers in a monolayer bounded by two solid, hydrophobic, plane boundaries.”
Physics of microswimmers—single particle motion and collective behavior: a review (2014, background): “These objects—called ”squirmers”—may also serve as a simple generic model for other types of microswimmers, for example the self- propelled droplets mentioned above (Thutupalli et al., 2011).”
Active Particles in Complex and Crowded Environments (2016, methodology): “Experimentally, this has been demonstrated, e.g., in a system of water droplets (containing bromine) suspended in an oil phase and stabilized by a surfactant (Schmitt and Stark, 2013; Thutupalli et al., 2011).”
Minimal model of active colloids highlights the role of mechanical interactions in controlling the emergent behavior of active matter (2015, background): “These include autophoretic colloids [5, 6, 17], rollers [18], and droplets [19].”
Phoretic self-propulsion at finite Péclet numbers (2014, background): “It also certainly plays an important role in the case of motion driven by surfactant gradients where, due to much smaller molecular diffusivity, Péclet numbers can easily reach O(100) [42].”