Solvent-free synthesis of superhydrophobic materials with self-regenerative and drag reduction properties

Abstract

Despite many exquisite properties, the use of superhydrophobic materials have been limited due issues with long-term durability, and use of solvents and chemicals. In present work, cost effective, and solvent-free approach was used to fabricate flexible superhydrophobic composite materials with self-regenerative and low-drag characteristics. Variation in reinforced particle’s fraction directly influenced the morphology, de-wettability and mechanical stability. The increase in particle concentration (polytetrafluoroethylene (PTFE)) resulted in decrease in surface skewness and kurtosis indicating formation of plateau-type morphology. De-wetting and adhesion showed a non-linear trend with minimum values observed for composite with 60 vol% reinforced particles. The composition was optimized based on high de-wetting, low adhesion and high mechanical strength. The optimized composite composition consisted of homogenous globular morphology with advancing and receding angles in excess of 150°, low tilting (5°) angle and lowest adhesion of ∼ 20 µN (more than ten times lower than PTFE). The high de-wetting of the composite was due to presence of stable Cassie state resisting the liquid impalement even against lower surface tension liquids and increased normal loads on droplets. The composite demonstrated both chemical and physical self-regeneration capability in real time during long-term abrasion, maintaining contact angles in excess of 150° and 5° tilting angle. The superhydrophobic material also showed extremely low drag (100 times lower than polydimethylsiloxane) to droplet mobility with friction forces around 5–12 µN, depending upon droplet size. Owing to sustainable nature, the synthesized functional composite can be used in multiple engineering systems.