Retarding spreading of surfactant drops on solid surfaces: Interplay between the Marangoni effect and capillary flows

Cellulose Nanocrystal Laden Oil–Water Interfaces: Interfacial Viscoelasticity, Emulsion Stability, and the Dynamics of Three-Phase Contact-Lines

“…This regime is transitioned into a viscous dominated regime with an apparent exponent of ∼0.8, finally reaching the late-time Tanner regime at ∼7 s. The delay in the initial fast motion of three-phase contact lines in the presence of surfactants (sodium dodecyl sulfate) has been previously characterized . It is reported that the nonuniform distribution of surfactants at the oil–water interface can generate Marangoni flows, which can consequently slow down the drainage of the oil thin film, thus delaying the fast spread of the drop on the solid …”

“…We capture the images from the bottom of the glass surface, measure the spreading area, and calculate the spreading radius ( r ( t )). The details of the experimental setup are discussed elsewhere. , We use DI water, CTAB 0.5 CMC solution, and CNC 1.00 wt %–CTAB 0.5 CMC dispersion as the drop phase. We first present the spreading dynamics of DI water and surfactant drops (CTAB 0.5 CMC) and then show the effect of adding CNC particles in the spreading of CNC-CTAB drop (CNC 1.00 wt %–CTAB 0.5 CMC).…”

“…The spreading dynamics is characterized by a power-law function as r ( t ) ∼ t α , where α = dlog­( r )/dlog­( t ) is plotted in Figure b. For the DI-water drop (γ eq = 42 mN/m, θ eq = 78°), there is an initial fast dynamic with an apparent exponent 0.8 ≤ α ≤ 1, known as the viscous dominated regime, − which reaches the late-time Tanner regime with a characteristic exponent of 0.1 at about ∼0.6 s. − For the CTAB drop (γ eq = 9 mN/m, θ eq = 74°), there is an initial retardation regime that lasts 140 ms with a characteristic exponent of ∼0.3. This regime is transitioned into a viscous dominated regime with an apparent exponent of ∼0.8, finally reaching the late-time Tanner regime at ∼7 s. The delay in the initial fast motion of three-phase contact lines in the presence of surfactants (sodium dodecyl sulfate) has been previously characterized .…”

“…For the DI-water drop (γ eq = 42 mN/m, θ eq = 78°), there is an initial fast dynamic with an apparent exponent 0.8 ≤ α ≤ 1, known as the viscous dominated regime, − which reaches the late-time Tanner regime with a characteristic exponent of 0.1 at about ∼0.6 s. − For the CTAB drop (γ eq = 9 mN/m, θ eq = 74°), there is an initial retardation regime that lasts 140 ms with a characteristic exponent of ∼0.3. This regime is transitioned into a viscous dominated regime with an apparent exponent of ∼0.8, finally reaching the late-time Tanner regime at ∼7 s. The delay in the initial fast motion of three-phase contact lines in the presence of surfactants (sodium dodecyl sulfate) has been previously characterized . It is reported that the nonuniform distribution of surfactants at the oil–water interface can generate Marangoni flows, which can consequently slow down the drainage of the oil thin film, thus delaying the fast spread of the drop on the solid …”

How molecular effects affect solutal Marangoni convection

“…It is a powerful effect, requiring only small interfacial tension gradients to create strong convective flows. Such gradients arise naturally by the addition of a surfactant at a liquid interface, as has been studied in various configurations using both experiments [3] and continuum fluid dynamics simulations [4]. This solutal Marangoni effect plays a role in many phenomena, in particular foam and emulsion formation and evolution [5].…”