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

Bionic Ring Grooves Design and Experiment of the Suction Cup Applied in Oil-Immersed Substrate

The vacuum suction cup is often used as an end effector and widely used in wall-climbing operations. However, there are few vacuum suction cup designs and applications for oil-immersed substrates. Inspired by the surface morphology of the octopus sucker, bionic suction cups with different numbers, diameters, and spacings of the ring grooves were designed. Their normal adsorption force was evaluated on the untreated and polished steel plate in oil. The test results showed that ring grooves positively affected the adsorption force. The bionic suction cup with a groove number of 3, a diameter of 0.5 mm, and a spacing of 3 mm was the most excellent in the test. It achieved normal adsorption forces of 54.83 ± 0.48 N and 43.89 ± 0.69 N on the untreated and polished steel plate. Compared with the standard suction cup, it increased by 32.31% and 12.28% on the untreated and polished steel plate. The regression model between the normal adsorption force and design factors was established based on the adsorption force test results, and the influence law of the ring groove structure parameters on the adsorption force of suction cups on oil-immersed substrates was analyzed. The order of significant effects of groove design parameters on normal adsorption forces was groove diameters, spacings, and numbers. The finite element analysis (FEA) results show that the ring grooves could significantly increase the contact pressure, frictional stress, and sliding distance between the suction cup and the substrate. The ring groove structure effectively improves the adsorption force of the suction cup on the oil-immersed surface by forming a more effective seal and increasing the friction force and adsorption area. This study could provide a reference for developing the actuator of the oil-immersed or lubricated climbing machine

Advanced Bionic Attachment Equipment Inspired by the Attachment Performance of Aquatic Organisms: A Review

In nature, aquatic organisms have evolved various attachment systems, and their attachment ability has become a specific and mysterious survival skill for them. Therefore, it is significant to study and use their unique attachment surfaces and outstanding attachment characteristics for reference and develop new attachment equipment with excellent performance. Based on this, in this review, the unique non-smooth surface morphologies of their suction cups are classified and the key roles of these special surface morphologies in the attachment process are introduced in detail. The recent research on the attachment capacity of aquatic suction cups and other related attachment studies are described. Emphatically, the research progress of advanced bionic attachment equipment and technology in recent years, including attachment robots, flexible grasping manipulators, suction cup accessories, micro-suction cup patches, etc., is summarized. Finally, the existing problems and challenges in the field of biomimetic attachment are analyzed, and the focus and direction of biomimetic attachment research in the future are pointed out

Effect of Groove Texture on Deformation and Sealing Performance of Engine Piston Ring

During the present study, a double groove texture was designed on the surface of a piston ring to improve the sealing performance between the piston ring and cylinder liner. The experimental design method was used to fabricate the test plan according to the groove width, depth, and spacing. By using the thermal–structural coupling analysis method, the finite element analysis of the standard piston ring and the textured piston ring was carried out to simulate the deformation state of the cylinder liner system of the piston ring group during the working stroke. The piston rings with different parameters designed by the test scheme were manufactured by wire electrical discharge machining, and the self-made experiment device carried out the sealing test. The results showed that the groove texture could improve the sealing performance of the piston ring, and the analyzed results demonstrated that the groove texture had little effect on the maximum deformation of the piston ring. Still, it could significantly reduce the minimum deformation of the piston ring group. A piston ring with groove texture would improve the sealing performance and reduce the deformation during the work stroke. During the test, the average deformation of the No.7 piston ring group, with a groove depth of 1 mm, a groove width of 0.5 mm, and a groove spacing of 0.1 mm, was the smallest, about 29.6% lower than that of the standard piston ring group. The sealing performance of the No.7 piston ring group was the best, and the reduction rate of the top gas leakage rate was 52.18%. During the present study, the sealing performance of the piston ring was improved by designing the grooved structure on the piston ring surface, thereby improving the fuel economy and power performance of the engine. The present study could provide a reference for the engineering field to design a piston ring with high sealing performance

Formation mechanism of freezing interface strain and effect of different factors on freezing interface strain

Changes in the freezing interface during the freezing process were studied to explain the ice-adhesion mechanism. The formation and variation of the freezing interface strain for different volumes of water on an aluminum alloy at different ambient temperatures were tested. The experimental results showed that the interface strain had the same formation and variation law despite the volume of water and ambient temperature. The freezing interface strain formation process could be separated into decreasing, rapidly increasing, and stable stages. The freezing interface strain gradually increased with lower ambient temperatures or an increase in the volume of water. Combined with the freezing process, the freezing time of the attached water and the formation time of the swelling force were reduced with decreasing ambient temperatures. The ice-adhesion area was small, so the freezing interface strain increased. When the volume of water increased, although the contact area between the ice and the substrate increased, so did the internal energy in the water, leading to an increase in the swelling force, increasing the interface strain. This study helped analyze the ice-adhesion formation process and its strength (based on its mechanical properties) to lay a theoretical foundation for developing process-intervention anti/de-icing technology

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

Effects of Discontinuous Thermal Conductivity of a Substrate Surface on Ice Adhesion Strength

This study proposes a novel anti-icing model in which silicone rubber with low thermal conductivity is coated at different positions on a material surface to change the continuity of the thermal conductivity of the surface. During the test, the surfaces of aluminum alloy and polymethyl methacrylate (PMMA) are discontinuously coated with silicone rubber. Repeated experiments are conducted to verify the anti-icing effect of the proposed model. Results showed that compared to the conventional surface ice adhesion strength, the rate of reduction of the ice adhesion strength of the aluminum alloy and PMMA could reach 75.07% and 76.70%, respectively, when the novel method is used. Because of the different levels of thermal conductivity at different positions on the material surface, the water attached to the surface locations without the coated silicone rubber had other freezing times. Combined with the heat and phase change of water during the freezing process, changing the stability of the interface between the ice and substrate could act as an active anti-icing power. The ice adhesion strength on the material surface could then be reduced. Compared with the conventional anti-icing methods, the anti-icing method proposed in this study could significantly increase the active anti-icing characteristics of the material and provide a novel anti-icing method for use in engineering applications

Comprehensive performance evaluation of coordinated development of industrial economy and its air pollution control

Exploring coordinated pathways that can promote not only the sustainable development of the industrial economy but also air quality is of great significance for the prevention and control of air pollution in China. Currently, the joint development pathways of the industrial economy-environment nexus remain unclear and poorly evaluated. In this study, we proposed a comprehensive performance evaluation combining objective and subjective weighting to identify industrial enterprises' economic-environment nexus benefits. It would be one of the most important steps to explore the coordinated pathways. Based on data envelopment analysis (DEA), the proposed method integrated with the index integration was used to evaluate the comprehensive performances of 41 industrial sectors in China's 13th five-year plan (2016–2020). Evaluation results showed that the comprehensive performances of the economy-environment nexus of the industrial sectors varied significantly, with the five-year average comprehensive technical efficiency (TE) of 0.11–1. Overall, the best two performances were realized by the industries of equipment manufacturing and living consumption, whereas the worst one belonged to the industry of bulk raw materials, with average comprehensive TE values of 0.50, 0.43, and 0.19, respectively. The results of the quantitative evaluation were consistent with those of the qualitative analysis in terms of the developmental status of the industrial sectors. According to the analyses of pure technical efficiency and scale effect, the proposed method identified the industrial sectors with the highest developmental value and with the highest need to control air pollution. Compared with those of the original DEA model, the results of the proposed method showed pronounced differences in terms of the performances of industrial sectors with high energy consumption and high particulate matter (PM) emissions and with low energy consumption and low PM emissions. The proposed evaluation method combining the weighting was suitable for identifying the comprehensive performance of the industrial economy-environment nexus and provides the basis for the prevention and control of air pollution

Bionic Ring Grooves Design and Experiment of the Suction Cup Applied in Oil-Immersed Substrate

The vacuum suction cup is often used as an end effector and widely used in wall-climbing operations. However, there are few vacuum suction cup designs and applications for oil-immersed substrates. Inspired by the surface morphology of the octopus sucker, bionic suction cups with different numbers, diameters, and spacings of the ring grooves were designed. Their normal adsorption force was evaluated on the untreated and polished steel plate in oil. The test results showed that ring grooves positively affected the adsorption force. The bionic suction cup with a groove number of 3, a diameter of 0.5 mm, and a spacing of 3 mm was the most excellent in the test. It achieved normal adsorption forces of 54.83 ± 0.48 N and 43.89 ± 0.69 N on the untreated and polished steel plate. Compared with the standard suction cup, it increased by 32.31% and 12.28% on the untreated and polished steel plate. The regression model between the normal adsorption force and design factors was established based on the adsorption force test results, and the influence law of the ring groove structure parameters on the adsorption force of suction cups on oil-immersed substrates was analyzed. The order of significant effects of groove design parameters on normal adsorption forces was groove diameters, spacings, and numbers. The finite element analysis (FEA) results show that the ring grooves could significantly increase the contact pressure, frictional stress, and sliding distance between the suction cup and the substrate. The ring groove structure effectively improves the adsorption force of the suction cup on the oil-immersed surface by forming a more effective seal and increasing the friction force and adsorption area. This study could provide a reference for developing the actuator of the oil-immersed or lubricated climbing machine

A Review of Bioinspired Vibration Control Technology

Due to huge demand in engineering, vibration control technology and related studies have always been at the frontiers of research. Although traditional vibration control methods are stable and reliable, they have obvious shortcomings. Through evolution and natural selection, certain body-parts of animals in the natural world have been cleverly constructed and well designed. This provides a steady stream of inspiration for the design of vibration control equipment. The prime objective of this review is to highlight recent advances in the bionic design of vibration control devices. Current bionic vibration control devices were classified, and their bionic principles were briefly described. One kind was the bionic device based on the brain structure of the woodpecker, which is mostly used to reduce vibration at high frequencies. Another kind of bionic device was based on animal leg structure and showed outstanding performance in low frequency vibration reduction. Finally, we briefly listed the problems that need to be solved in current bionic vibration control technology and gave recommendations for future research direction