1 research outputs found
A simple model for self-propulsion of microdroplets in surfactant solution
We propose a simple active hydrodynamic model for the self-propulsion of a
liquid droplet suspended in micellar solutions. The self-propulsion of the
droplet occurs by spontaneous breaking of isotropic symmetry and is studied
using both analytical and numerical methods. The emergence of self-propulsion
arises from the slow dissolution of the inner fluid into the outer micellar
solution as filled micelles. We propose that the surface generation of filled
micelles is the dominant reason for the self-propulsion of the droplet. The
flow instability is due to the Marangoni stress generated by the non-uniform
distribution of the surfactant molecules on the droplet interface. In our
model, the driving parameter of the instability is the excess surfactant
concentration above the critical micellar concentration which directly
correlates with the experimental observations. We consider various low-order
modes of flow instability and show that the first mode becomes unstable through
a supercritical bifurcation and is the only mode contributing to the swimming
of the droplet. The flow fields around the droplet for these modes and their
combined effects are also discussed.Comment: 8 pages, 5 figure