Research Progress of Superhydrophobic Materials in the Field of Anti-/De-Icing and Their Preparation: A Review.

Accumulated ice has brought much damage to engineering and people's lives. The accumulation of ice can affect the flight safety of aircraft and lead to the failure of cables and power generation blades; it can even cause damage to human life. Traditional anti-icing and de-icing strategies have many disadvantages such as high energy consumption, low efficiency, or pollution of the environment. Therefore, inspired by animal communities, researchers have developed new passive anti-icing materials such as superhydrophobic material. In this paper, the solid surface wetting phenomenon and superhydrophobic anti-icing and de-icing mechanism were introduced. The methods of fabrication of superhydrophobic surfaces were summarized. The research progress of wear-resistant superhydrophobic coatings, self-healing/self-repairing superhydrophobic coatings, photothermal superhydrophobic coatings, and electrothermal superhydrophobic coatings in the field of anti-icing and de-icing was reviewed. The current problems and challenges were analyzed, and the development trend of superhydrophobic materials was also prospected in the field of anti-icing and de-icing. The practicality of current superhydrophobic materials should continue to be explored in depth.

Modeling of geometry and insertion force of a new lancet medical needle.

Lancet needle is a typical medical treatment device. Its tip consists of two lancet planes and one bevel plane. When the lancet needle is inserted into soft organ tissue, the insertion force may influence the needle cutting direction and treatment effect and increase the pain. One of the main factors affecting this insertion force is the geometry of the needle tip. Based on the research on the shape and processing method of the conventional lancet needle, a new lancet needle tip geometry was obtained by adjusting the relative position of the grinding wheel to the needle. A mathematical model of this new lancet needle was established. The relationship between processing parameters and needle shape was analyzed, and the needle insertion force was predicted. Compared with the conventional lancet needle, the new lancet needle is sharper, and the insertion force on the cutting edge is smaller. However, this change in the grinding position of the needle lancet plane has a great influence on the shape of needle tip near the intersection of the bevel plane and the lancet plane. Some special second bevel angle and rotated angle will cause a large change in the specific force at the intersection place, which is not conducive to reducing the insertion force.

Experimental study on frost-formation characteristics on cold surface of arched copper sample.

The present work investigates the process of frosting formation on arched copper samples with different surface temperatures, calculated the thickness of the frost layer by using the scale method, and analyzed frost lodging, melting, and other phenomena that appeared during the frost-formation process. The results showed that the frosting process on an arched surface can be divided into ice-film formation, rapid growth of the frost layer, and stable growth of the frost layer. Meanwhile, the phenomena of frost-branch breakage, lodging, and melting were observed. The surface temperature had a large effect on the frost formation and thickness of the frost layer, e.g., the formation time of the ice film on a surface at -5°C was the longest (~135 s), the frost layer formed on a surface at -20°C was the thickest (~660 µm). When microscopic observation of the frosting process was accompanied by calculation of the frost-layer thickness, it could be seen that the appearance of the frost branches was affected by the different thermal conductivities of the frost layers, undulating surface of the ice film, and temperature difference between the layers. The changes in the frost branches and the soft surface of the frost layer also affected the growth of the frost layer. The findings of this study are expected to provide guidelines for optimization of conventional defrosting methods.

Hydrophobic durability characteristics of butterfly wing surface after freezing cycles towards the design of nature inspired anti-icing surfaces.

The hydrophobicity and anti-icing performance of the surfaces of some artificial hydrophobic coatings degraded after several icing and de-icing cycles. In this paper, the frost formation on the surfaces of butterfly wings from ten different species was observed, and the contact angles were measured after 0 to 6 frosting/defrosting cycles. The results show that no obvious changes in contact angle for the butterfly wing specimens were not obvious during the frosting/defrosting process. Further, the conclusion was inferred that the topography of the butterfly wing surface forms a special space structure which has a larger space inside that can accommodate more frozen droplets; this behavior prevents destruction of the structure. The findings of this study may provide a basis and new concepts for the design of novel industrially important surfaces to inhibit frost/ice growth, such as durable anti-icing coatings, which may decrease or prevent the socio-economic loss.