Spherical-micelle-driven deposition of high-speed impacting water droplets on superhydrophobic surfaces

Abstract

Controlling the deposition and spread of high-speed impacting water droplets on superhydrophobic surfaces is crucial in numerous applications. Modulating self-assembled surfactant structures has been recently proved to be an efficient strategy. However, small spherical micelles, as a more straightforward encapsulation system, could not show this performance, as reported previously. Herein, a small spherical micelle of sodium dodecyl sulfate (SDS), upon micellar surface modification by branched organic cations (TAAB-n), enables high-speed impacting water droplets to completely deposit and spread on a superhydrophobic surface. The complete deposition and spread require that the micelles show stronger interaction with the micro/nanostructures of the superhydrophobic surface, higher surface activity, and more rapid molecular diffusion. Otherwise, the water droplets will rebound or splash off the superhydrophobic surface if the micelles exhibit faster molecular diffusion but cannot closely interact with the newly impact-created liquid/solid interface, or if the micelles grow into large spherical aggregates due to enhanced hydrophobic interaction among the SDS and TAAB-n molecules and thereby limit the molecular diffusion and replenishment to the liquid/solid interface. This work opens a way to utilize modified small spherical micelles to inhibit the rebound and splash of high-speed impacting droplets on superhydrophobic surfaces.