The authors demonstrate that pH or ionic concentration gradients across a liquid metal droplet induce both deformation and surface Marangoni flow
Stronger surface tension difference enhances the Marangoni flow and consequently destabilizes the film.
From the proposed mechanism for top layer dewetting discussed in the previous session, it is clear that small disturbances on the interface may accelerate the marangoni flow and affect the critical top layer thickness at the onset of dewetting.
This Marangoni flow ultimately may lead to dewetting of the top layer, even for cases at which the surface tension of the top layer is lower than that of the bottom layer.
Here, we will focus on modelling a new type of artificial microswimmers where propulsion is achieved by Marangoni flow
Sufactant adsorbtion and Marangoni flow
in liquid jets.
This is understood by inspection of Figure 18, which shows that a phase-shift occurs between the film thickness and the surfactant surface concentration that results in a situation wherein the concentration is larger downstream of the wave peak than upstream; this drives the retarding Marangoni flow.
Surfactants lower the liquid surface tension, which promotes wave formation but they also give rise to surface tension gradient-driven or Marangoni flow.
The degree of BLRO depends on competing flows--surface-tension-gradient Marangoni flow increases BLRO while pressure-gradient flow decreases BLRO.
In Marangoni flow the time rate of change in film thickness depends on the film thickness squared
Hence, leveling dominates over Marangoni flow for thick films.
Since the velocity of Marangoni flow is inversely proportional to viscosity (Eq 10).