Designing Self-Healing Superhydrophobic Surfaces with Exceptional Mechanical Durability

Abstract

The past decade saw a drastic increase in the understanding and applications of superhydrophobic surfaces (SHSs). Water beads up and effortlessly rolls off a SHS due to its combination of low surface energy and texture. Whether being used for drag reduction, stain repellency, self-cleaning, fog harvesting, or heat transfer applications (to name a few), the durability of a SHS is critically important. Although a handful of purportedly durable SHSs have been reported, there are still no criteria available for systematically designing a durable SHS. In the first part of this work, we discuss two new design parameters that can be used to develop mechanically durable SHSs via the spray coating of different binders and fillers. These parameters aid in the rational selection of material components and allow one to predict the capillary resistance to wetting of any SHS from a simple topographical analysis. We show that not all combinations of sprayable components generate SHSs, and mechanically durable components do not necessarily generate mechanically durable SHSs. Moreover, even the most durable SHSs can eventually become damaged. In the second part, utilizing our new parameters, we design and fabricate physically and chemically self-healing SHSs. The most promising surface is fabricated from a fluorinated polyurethane elastomer (FPU) and the extremely hydrophobic small molecule 1H,1H,2H,2H-heptadecafluorodecyl polyhedral oligomeric silsesquioxane (F-POSS). A sprayed FPU/F-POSS surface can recover its superhydrophobicity even after being abraded, scratched, burned, plasma-cleaned, flattened, sonicated, and chemically attacked.

Rapid and Repeatable Self‐Healing Superoleophobic Porous Aluminum Surface Using Infiltrated Liquid Healing Agent

“…Self‐healing superoleophobic surfaces have been reported recently . Zhou et al and Wang et al reported the self‐healing superhydrophobic and superoleophobic properties of fabric coatings prepared from a mixture of fluorinated decyl polyhedral oligomeric silsesquioxane and hydrolyzed fluorinated alkylsilane or by an easily available material system consisting of poly(vinylidene fluoride‐ co ‐hexafluoropropylene), fluoroalkylsilane, and modified silica nanoparticles.…”

Superomniphobic Surfaces with Improved Mechanical Durability: Synergy of Hierarchical Texture and Mechanical Interlocking

“…During one abrasion cycle, the surface moved back and forth on the sandpaper with a total travel distance of 5 cm. Since both the superomniphobic surface and the sandpaper are textured, we anticipate that the local shear stress experienced by the superomniphobic surface is much higher than 1 kPa . Our results indicate that the apparent contact angles decrease ( Figure a) and roll‐off angles increase (Figure b) with the increasing abrasion cycles for both water and n ‐hexadecane.…”

Facile Design and Fabrication of Superwetting Surfaces with Excellent Wear-Resistance

“…Self-repair with the aid of external stimuluses allows periodically renewable non-wettability even if repeated wear occurs on topography, but suffers from low regeneration rates or laborious procedures. 27,29,35,[57][58][59][60] Wear-induced wettability regeneration as previously described is available to the superhydrophilic surfaces, but it has been little resultful for the renovation of superhydrophobic surfaces, on which more rigid patterns are required for the water/gas/solid three-phase system. Some studies reveal that superimposed roughness can be renewed through wear without degeneration of superhydrophobicity, nevertheless not accessible at significant wear.…”

“…For superhydrophilic surfaces, compression/tensile measurements, 18,19 approach force, 18 nanoindentation, 20 sand grain impact, 19,20 finger wipe, 19 tape peeling 19 and linear abrasion 21 were adopted in a few literatures. More methods in tribology have been concerned and introduced into the durability assessment of superhydrophobic surfaces, including tangential abrasion, [22][23][24][25][26][27][28][29] blade/knife scratching, 22,24,25,[27][28][29] pencil hardness tests, 30,31 finger wiping, 22,24,25 sand grain impact, 30,32 water jet tests, 33,34 laundering tests, 29,35 etc. The linear abrasion test is always recommended as the most principal means for evaluating the mechanical durability of superhydrophobic surfaces against wear.…”