Skip to Main content Skip to Navigation
Journal articles

Nonlinear dynamics of a chemically-active drop: From steady to chaotic self-propulsion

Abstract : Individual chemically active drops suspended in a surfactant solution were observed to self-propel spontaneously with straight, helical, or chaotic trajectories. To elucidate how these drops can exhibit such strikingly different dynamics and "decide" what to do, we propose a minimal axisymmetric model of a spherical active drop, and show that simple and linear interface properties can lead to both steady self-propulsion of the droplet as well as chaotic behavior. The model includes two different mobility mechanisms, namely, diffusiophoresis and the Marangoni effect, that convert self-generated gradients of surfactant concentration into the flow at the droplet surface. In turn, surface-driven flow initiates surfactant advection that is the only nonlinear mechanism and, thus, the only source of dynamical complexity in our model. Numerical investigation of the fully-coupled hydrodynamic and advection diffusion problems reveals that strong advection (e.g., large droplet size) may destabilize a steadily self-propelling drop; once destabilized, the droplet spontaneously stops and a symmetric extensile flow emerges. If advection is strengthened even further in comparison with molecular diffusion, the droplet may perform chaotic oscillations. Our results indicate that the thresholds of these instabilities depend heavily on the balance between diffusiophoresis and the Marangoni effect. Using linear stability analysis, we demonstrate that diffusiophoresis promotes the onset of high-order modes of monotonic instability of the motionless drop. We argue that diffusiophoresis has a similar effect on the instabilities of a moving drop.
Document type :
Journal articles
Complete list of metadata

Cited literature [32 references]  Display  Hide  Download

https://hal.archives-ouvertes.fr/hal-02104839
Contributor : Sébastien Michelin Connect in order to contact the contributor
Submitted on : Tuesday, November 12, 2019 - 4:15:38 PM
Last modification on : Tuesday, May 18, 2021 - 11:06:05 AM
Long-term archiving on: : Thursday, February 13, 2020 - 6:44:29 PM

File

1901.02263.pdf
Files produced by the author(s)

Identifiers

Citation

Matvey Morozov, Sébastien Michelin. Nonlinear dynamics of a chemically-active drop: From steady to chaotic self-propulsion. Journal of Chemical Physics, American Institute of Physics, 2019, 150 (4), pp.044110. ⟨10.1063/1.5080539⟩. ⟨hal-02104839⟩

Share

Metrics

Record views

28

Files downloads

26