Effect of Interaction of Nanoparticles and Surfactants on the Spreading Dynamics of Sessile Droplets

Abstract

While a body of literature on the spreading dynamics of surfactants and a few studies on the spreading dynamics of nanocolloids exist, to the best of the authors' knowledge, there are no reports on the effect of presence of surfactants on the spreading dynamics of nanocolloidal suspensions. For the first time the present study reports an extensive experimental and theoretical study on the effect of surfactant impregnated nanocolloidal complex fluids in modulating the spreading dynamics. A segregation analysis of the effect of surfactants alone, nanoparticle alone, and the combined effect of nanoparticle and surfactants in altering the spreading dynamics have been studied in detail. The spreading dynamics of nanocolloidal solutions alone and of the surfactant impregnated nanocolloidal solutions are found to be grossly different, and particle morphology is found to play a predominant role. For the first time the present study experimentally proves that the classical Tanner's law is disobeyed by the complex fluids in the case of particle alone and combined particle and surfactant case. We also discuss the role of imbibitions across the particle wedge in the precursor film in tuning spreading dynamics. We propose an analytical model to predict the nature of dependency of contact radius on time for the complex colloids. A detailed theoretical examination of the governing factors, the interacting forces at the three phase contact line, and the effects of interplay of surfactants and the nanoparticles at the precursor film in modulating the spreading dynamics has been presented for such complex colloids.

Spreading of Micrometer-Sized Droplets under the Influence of Insoluble and Soluble Surfactants: A Numerical Study

“…They found that a slower surfactant supply from the bulk towards the leading edge leads to a Marangoni flow towards the three phase contact line, resulting in faster spreading. In their case, the surfactant showed the opposite influence on wetting compared to [5].…”

“…However, typical inks show a more complex behavior due to the presence of the pigments and surface active substances, so-called surfactants. Harikrishnan et al [5] studied the spreading of sessile droplets under the influence of nanoparticles and surfactants, focusing on the interaction between surfactants and nanoparticles. For both nanocolloidal systems with and without surfactant present, they found a deviation from Tanner's Law [6] d ∝ t n , where d is the wetted diameter and t stands for time.…”

Superspreading and Drying of Trisiloxane-Laden Quantum Dot Nanofluids on Hydrophobic Surfaces

“…[36][37][38][39] Interactions of nanofluids with solids, however, involve much more complex physical and chemical processes on different length scales behind them if, besides nanoparticles, surfactants are added to a base fluid. 40 Despite a widespread interest and intensive investigations, the information on the surfactant-laden nanosuspension wetting behavior is still quite limited and inconclusive. To the best of authors' knowledge, a recent study on spreading dynamics of nanofluids containing surfactant presented by Harikrishnan et.al.…”

“…To the best of authors' knowledge, a recent study on spreading dynamics of nanofluids containing surfactant presented by Harikrishnan et.al. 40 is still the only work comparing wetting behavior of surfactant-laden nanosuspensions with water-based nanosuspensions and particle-free surfactant solutions. It has been found out that in complex systems consisting of nanoparticles and surfactants, the latter dominate spreading dynamics.…”

“…Conventional SDS and CTAB surfactants were used in their investigation. 40 If the surface energy of solid is low, a major part of commonly used surfactants can only decrease contact angle but do not provide complete wetting of surface. It was shown, for instance, by Dutschk et.al.…”