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The fundamental understanding of the icephobic performance of two model superhydrophobic surfaces (lotus and petal surfaces) is important for many industrial applications. The effect of wettability and surface energy on ice adhesion has recently received attention. However, the verification of icephobicity is typically carried out with a single observation method. For this study, rough modified rod-coated surfaces, structured polymer surfaces and nine smooth surfaces with tunable wettability were fabricated. Combining several observation techniques of icephobicity indicate that petal and lotus surfaces lose their superhydrophobicity, being less useful for ice repellency due to poor humidity tolerance in condensation conditions. The ice adhesion of rough surfaces enhanced with increasing hydrophobicity. The increased interface area leads to a reduction of the icephobic performance. The stress concentrator on the lotus surface was better than on the petal surface. In addition, the role of dynamic wettability on ice adhesion was checked. Smooth hydrophobic surfaces were found to be better icephobic materials compared to rough surfaces. The intrinsic surface energy of smooth surfaces is significantly linear with the ice adhesion. High freezing delay times were found for smooth low-density polyethylene resin and fluorinated surfaces.

Icephobic/anti-icing materials have received growing attentions due to their great potential in reducing energy consumption. The aim of this presented work is to propose a superhydrophobic surface with microblock-nanohair hierarchical structures, and verify its water repellence and icephobic capacity. The hierarchical structures were fabricated by means of a combined method of electrochemical etching and hydrothermal treatment. Following this, the fluoridation modification was performed to obtain the superhydrophobicity with the water contact angle reaching 164° and the sliding angle of 1.5°. The dynamic droplet impacting on the hierarchical structure surface can rapidly rebounce off with the shorter contact time of 9.8 ms, displaying the robust dynamic water repellency. Comparing with the untreated substrate, the resultant superhydrophobic surface exhibited higher anti-icing property with the freezing time of a 4 μL reference droplet increasing from 11.3 s to ∼1700 s at −10 °C, and the ice adhesion force reducing to ∼35 kPa. Furthermore, the comparative studies with the other single-tier structure (i.e., microblock and nanohair structure) surfaces provided the necessary assistance to reveal the underlying action mechanism that the hierarchical micro-nanostructure induced more air pockets underneath droplets to produce the higher hydrophobicity and icephobic capacity.

Although the superhydrophobic surfaces are preferable for passive anti-icing systems, as they provide water shedding before initiation of ice nucleation, their practical usage is still under debate. This is so, as the superhydrophobic materials are not necessarily icephobic and most of the synthesis techniques are characterized with low fabrication scalability. Here, we describe a rational strategy for the atmospheric icing prevention, based on chemically functionalized carbon soot, suitable for large-scale fabrication of superhydrophobic coatings that exhibit and retain icephobicity in harsh operational conditions. This is achieved through a secondary treatment with ethanol and aqueous fluorocarbon solution, which improves the coating’s mechanical strength without altering its water repellency. Subsequent experimental analyses on the impact dynamics of icy water droplets on soot coated aluminum and steel sheets show that these surfaces remain icephobic in condensate environments and substrate temperatures down to −35 °C. Furthermore, the soot’s icephobicity and non-wettability are retained in multiple icing/de-icing cycles and upon compressed air scavenging, spinning and water jetting with impact velocity of ∼25 m/s. Finally, on frosted soot surfaces, the droplets freeze in a spherical shape and are entirely detached by adding small amount of thermal energy, indicating lower ice adhesion compared to the uncoated metal substrates.

Four polydimethylsiloxane (PDMS) coatings with different surface free energies have been prepared and applied to smooth and roughened aluminum plates to form hydrophobic and superhydrophobic surfaces. Their surface wettability in terms of water contact angle (CA), sliding angle (SA) and water droplet impact dynamics was studied under an ambient (50% relative humidity, RH at 25 °C) and three different condensing environments (low, highly and extremely condensing, i.e. 30%, 60% and 90% RH at −10 °C). In addition, the surface ice adhesion was investigated under the extremely condensing condition. Different PDMS coatings on either smooth or roughened surfaces displayed a very similar impact to static and dynamic wettability under the ambient environment. However, the water impact behavior and ice adhesion under the extremely condensing condition between the hydrophobic and superhydrophobic surfaces are significantly different. One of the superhydrophobic surfaces (R2180) demonstrated an excellent water repelling capability to retard ice accumulation, and reduced ice adhesion strength even under the extremely condensing condition, and thus will be a good candidate for ice-phobic applications. This excellent ice-phobic property is attributed to the low surface free energy of the coating, which effectively prevents the water condensation inside the cavities of the hierarchical superhydrophobic structures and thus maintains “air cushion” on the solid/water interface, indicated by a very low solid-liquid contact area increase after surface is exposed to this condensing weather condition. This result demonstrates that the “air cushion” in a superhydrophobic surface could be maintained even under an extremely condensing condition by carefully selection of coating composition with a very low surface free energy.

A facile and durable biomimetic slippery anti-icing coating was prepared by infusing nontoxic and inexpensive lubricating silicone oil into superhydrophobic dual-scale micro/nano-structured (MNS) aluminum surfaces. Superhydrophobic surfaces were fabricated via the combination of simple chemical etching and anodization, followed by surface modification with poly(dimethylsiloxane) (PDMS). Compared to superhydrophobic coatings, silicone oil-infused polydimethylsiloxane (SOIP) coating displays a low ice-adhesion strength of 22 ± 5 kPa on the structured surface. Moreover, the SOIP coating sustained low ice-adhesion strength (35 ± 15 kPa) even when the temperature was lowered to −25 °C. The MNS-surface exhibits excellent durability, showing a low ice-adhesion (108 kPa) after 20 icing/de-icing cycles and long-term icephobicity (55 ± 13 kPa) after four months' exposure in ambient environment. We also examined the influence of surface morphology on ice-adhesion strength, the SOIP modified MNS-surface displays better anti-icing properties compared to a nano-structured (NS) surface under harsh conditions; icing/deicing and abrasion cycles. The MNS-surface act as reservoir to hold the excess amount of oil, thus reducing the loss of lubricant during icing/deicing cycles. The proposed technique is very simple and cost-effective, and most importantly it can be applied for production of durable and scalable anti-icing coatings for various practical applications.

This article studies the anti-ice performance of several micro/nano-rough hydrophobic coatings with different surface chemistry and topography. The coatings were prepared by spin-coating or dip coating and used organosilane, fluoropolymer or silicone rubber as a top layer. Artificially created glaze ice, similar to the naturally accreted one, was deposited on the nanostructured surfaces by spraying supercooled water microdroplets (average size ∼80 μm) in a wind tunnel at subzero temperature (−10 °C). The ice adhesion strength was evaluated by spinning the samples in a centrifuge at constantly increasing speed until ice delamination occurred. The results show that the anti-icing properties of the tested materials deteriorate, as their surface asperities seem to be gradually broken during icing/de-icing cycles. Therefore, the durability of anti-icing properties appears to be an important point for further research. It is also shown that the anti-icing efficiency of the tested superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top and between surface asperities takes place, leading to high values of ice adhesion strength. This implies that superhydrophobic surfaces may not always be ice-phobic in the presence of humidity, which can limit their wide use as anti-icing materials.

Fluoropolymer, because of the extremely low surface energy, could be non-stick to water and thus could be a good candidate as anti-icing materials. In this paper, the icephobic properties of a series of fluoropolymer materials including pristine PTFE plates (P-PTFE), sandblasted PTFE plates (SB-PTFE), two PTFE coatings (SNF-1 and SNF-CO1), a fluorinated room-temperature vulcanized silicone rubber coating (F-RTV) and a fluorinated polyurethane coating (F-PU) have been investigated by using SEM, XPS, ice adhesion strength (tensile and shear) tests, and static and dynamic water contact angle analysis. Results show that the fluoropolymer material with a smooth surface can significantly reduce ice adhesion strength but do not show obvious effect in reducing ice accretion at −8 °C. Fluoropolymers with sub-micron surface structures can improve the hydrophobicity at normal temperature. It leads to an efficient reduction in the ice accretion on the surface at −8 °C, due to the superhydrophobicity of the materials. But the hydrophobicity of this surface descends at a low temperature with high humidity. Consequently, once ice layer formed on the surface, the ice adhesion strength enhanced rapidly due to the existence of the sub-micron structures. Ice adhesion strength of fluoropolymers is highly correlated to CA reduction observed when the temperature was changed from 20 °C to −8 °C. This property is associated with the submicron structure on the surface, which allows water condensed in the interspace between the sub-micron protrudes at a low temperature, and leads to a reduced contact angle, as well as a significantly increased ice adhesion strength.

The aim of this study is to investigate the effects of surface roughness and surface energy on ice adhesion strength. Sandblasting technique was used to prepare samples with high roughness. Silicon-doped hydrocarbon and fluorinated-carbon thin films were employed to alter the surface energy of the samples. Silicon-doped hydrocarbon films were deposited by plasma-enhanced chemical vapor deposition, while fluorinated-carbon films were produced using deep reactive ion etching equipment by only activating the passivation step. Surface topographies were characterized using scanning electron microscopy and a stylus profilometer. The surface wetting properties were characterized by a video-based contact angle measurement system. The adhesion strength of ice formed from a water droplet on these surfaces was studied using a custom-built shear force test apparatus. It was found that the ice adhesion strength is correlated to the water contact angles of the samples only for surfaces with similar roughness: the ice adhesion strength decreases with the increase in water contact angle. The study also shows that smoother as-received sample surfaces have lower ice adhesion strength than the much rougher sandblasted surfaces.

In this study, ice adhesion strength on flat hydrophobic and rough super-hydrophobic coatings with similar surface chemistry (based on same fluoropolymer) is compared. Glaze ice, similar to naturally accreted, was prepared on the surfaces by spraying super-cooled water microdroplets at subzero temperature. Ice adhesion was evaluated by spinning the samples at constantly increasing speed until ice delamination occurred. Super-hydrophobic surfaces with different contact angle hysteresis were tested, clearly showing that the latter, along with the contact angle, also influences the ice–solid adhesion strength.