3.9 Article

Effect of Surfactant Dynamics on Flow Patterns Inside Drops Moving in Rectangular Microfluidic Channels

Journal

COLLOIDS AND INTERFACES
Volume 5, Issue 3, Pages -

Publisher

MDPI
DOI: 10.3390/colloids5030040

Keywords

multiphase flow; drop microfluidics; rectangular channel; flow pattern; corner flow; surfactant dynamics; aqueous/oil interface; Langmuir isotherm parameters; characteristic adsorption time

Funding

  1. Engineering and Physical Sciences Research Council, UK, through the PREMIERE Programme Grant [EP/T000414/1]
  2. EPSRC [EP/T000414/1] Funding Source: UKRI

Ask authors/readers for more resources

Experimental study shows that the influence of surfactants on moving droplets in a microfluidic channel depends on the characteristic adsorption time, which can significantly change the flow patterns inside the droplets.
Drops contained in an immiscible liquid phase are attractive as microreactors, enabling sound statistical analysis of reactions performed on ensembles of samples in a microfluidic device. Many applications have specific requirements for the values of local shear stress inside the drops and, thus, knowledge of the flow field is required. This is complicated in commonly used rectangular channels by the flow of the continuous phase in the corners, which also affects the flow inside the drops. In addition, a number of chemical species are present inside the drops, of which some may be surface-active. This work presents a novel experimental study of the flow fields of drops moving in a rectangular microfluidic channel when a surfactant is added to the dispersed phase. Four surfactants with different surface activities are used. Flow fields are measured using Ghost Particle Velocimetry, carried out at different channel depths to account for the 3-D flow structure. It is shown that the effect of the surfactant depends on the characteristic adsorption time. For fast-equilibrating surfactants with a characteristic time scale of adsorption that is much smaller than the characteristic time of surface deformation, this effect is related only to the decrease in interfacial tension, and can be accounted for by the change in capillary number. For slowly equilibrating surfactants, Marangoni stresses accelerate the corner flow, which changes the flow patterns inside the drop considerably.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

3.9
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available