This super waterproof coating also features efficient material loading and powerful self-cleaning properties!

After the duck came ashore from the river, it was found that its feathers did not have any traces of water contact.

After the rain in summer, there will be rows of small water droplets on the lotus leaf.

That's the magic of super-repulsive surfaces! Super-repellent surfaces are a class of surfaces with non-wetting/non-staining properties that have a wide range of applications where reduced drag, low contamination, enhanced cargo loading and/or controlled liquid transport are required

According to the principle of "biomimicry" of nature, Dr.

The related work was published in Advanced Science as "Exploiting Molecular Dynamics in Composite Coatings to Design Robust Super-Repellent Surfaces"

 # POSS - Preparation of Adhesive Coatings

The team used a two-component coating system containing a polymerizable binder (ethyl cyanoacrylate, ECA) that exhibits high levels of binding affinity

As a precursor, POSS has low energy and can also act as a nucleating agent, forming a porous structure with rough layers, which helps to maintain the air layer on the surface of the coating, which contributes to the super-repulsion

Fig.

 # Physicochemical properties of POSS-adhesive coatings

and hyperexclusion

After coating with the POSS-binder composite, the roughness of the smooth mica substrate (≈0.
1 nm) was significantly increased by a factor of about 1000, and this phase separation contributed to the formation of repelling surfaces (i.
e.
, the air capture)
.
Based on the principle of minimum free surface energy, a small amount of low-energy modification can significantly reduce the surface energy of the entire composite
.
The total surface energy of the composite decreases with the increase of POSS content, and its minimum surface energy is about 10 mJ m−2 when the POSS content is >10 wt%
.

Furthermore, the annealing treatment at 200 °C did not alter the surface of the binder or the surface of the composite, indicating their potential application at high temperatures
.
In conclusion, the cohesive properties of the binder and the low-energy properties of the POSS jointly determine the super-repellent properties of the coating
.

Fig.
2 Planar composite coating (20% POSS) and its interface properties

Our spray-on POSS binder composites can form a uniform layered coating on the wire surface without clogging the inter-fiber spacing, allowing pores to reduce solid-liquid contact
.
The coated surface was able to resist the continuous impingement of ethanol droplets released at a distance of about 7 mm from the surface without liquid penetration (or wetting), indicating that it is also super-repellent to ultra-low surface tension liquids (ethanol)
.
Furthermore, the ultra-low contact angle hysteresis and roll-off angle together demonstrate ultra-low solid-liquid interactions in both vertical and lateral directions
.

Fig.
3 Spraying super-repellent POSS-binder paint

 #POSS - Adhesive Coating Stability

and robustness

The stability and robustness of hyperrepulsive surfaces are an important factor leading to practical applications
.
The breakthrough pressure (Pb, the minimum hydraulic pressure from non-wetting to wetting) is a measure of the robustness of the non-wetting state, and the Pb of the coating depends largely on the surface tension of the probe fluid, i.
e.
, Pb is maximum in water ( ≈1000 Pa), the lowest in pure ethanol (≈90 Pa), Pb can also be adjusted by the fiber spacing of the grid substrate, the smaller the spacing, the larger the Pb
.

Ultra-repellent coatings are also resistant to aggressive liquids, including concentrated acids and bases
.
In addition, POSS has excellent thermal stability, and the composite coating is also stable at high temperatures up to 150°C
.
In addition, there is no obvious chemical leaching after treatment with 10 kinds of chemical reagents, UV-O3, peeling test, etc.
, and it has excellent chemical stability and mechanical stability
.
Moreover, after 10 min incubation in the fluorescent solution, there was no obvious staining of the super-repellent coating, which further confirmed the robustness of the super-repellent coating
.

Figure 4 Stability of super-repellent coatings

 # Cargo Loading Application

The team further investigated the hyperrepulsive properties of the coated grid substrates when external forces were applied either statically or during motion
.
It turns out that the superspray-resistant coating has the potential to protect marine vehicles operating in harsh conditions, such as oil spill waterways, or the exploration of hydrocarbon lakes on Titan
.
In addition, the super-repellent property, loading capacity, and sliding motion on the liquid surface of the coating make it promising for drag reduction applications
.

Figure 5 Cargo Loading Application of Super Repellent Coating - Floating, Loading and Movement on Liquid Surface

summary

In conclusion, the team developed an engineered anti-spray coating and surface coating route using a universal binder and a low-energy precursor.
This two-component coating system combines the beneficial properties of both precursors and is a A promising approach to achieve durable hyperrepulsion on substrates such as stainless steel, copper, silicon, and mica
.
This work not only holds promise for chemical shielding, heat transfer, and liquid handling, but also provides a simple and reliable route for engineering advanced coatings by effectively combining the excellent properties of each component
.