ABSTRACT
Ice accumulation on surfaces significantly jeopardizes the operational security and economic effectiveness of equipment. As one of the efficient anti-icing strategies, fracture-induced ice detachment strategy can realize low ice adhesion strength and is feasible for large-area anti-icing, but its application in harsh environment is restrained by mechanical robustness deterioration due to ultralow elastic moduli. It is still a challenge for fracture-promoted interfaces to reach ultralow ice adhesion and maintain strong mechanical robustness. Drawing inspiration from subcutaneous tissue, we propose a multiscale interpenetrating reinforcing method to develop a fracture-promoted ultraslippery ice detachment interface. Our approach minimizes elastic deformation and the stress threshold of fracture initiation during ice detachment, ensuring fast and noninjurious ice detachment on the interface. At the same time, this method reinforces the mechanical robustness of the fracture-promoted ultraslippery interface, making it possible to ensure long-term operation under harsh conditions. The superiority is revealed by ultralow ice adhesion strength below 20 kPa at -30 °C even after 200 continuous abrasion cycles, as well as efficient ice shedding during dynamic anti-icing tests, which is clarified by theoretical prediction and experimental verification. This work is expected to enlighten the design of next-generation durable anti-icing interface.
ABSTRACT
Inspired by a cactus spine and pitcher plant slippery surface, a strategy is proposed to design a superhydrophobic-hydrophilic conical copper needle (SHB-HL CCN) and hydrophilic slippery rough surface (SRS) integrative system. In this strategy, the SHB-HL CCN was inserted vertically on the hydrophilic SRS, and such a hydrophilic SRS + SHB-HL CCN system exhibited a high-efficiency cycle in droplet capture-coalescence (supply)-transport during the fog collection process. Even with a single SHB-HL CCN or hydrophilic SRS, the water collection rate is much higher than that of the usual materials (original copper needle, superhydrophobic substrate, hydrophobic SRS, etc.). It is demonstrated that a newly enhanced fog harvesting mechanism and higher fog collection rate can be realized due to the synergy between the Laplace pressure difference from the conical needle, wettability force of wettability difference in the conical copper needles, and released surface energy in droplet coalescence in addition to the attracting force from water bridges formed between needles and substrate. Compared with a single SHB-HL CCN and hydrophilic SRS, the water collection rate of the hydrophilic SRS + SHB-HL CCN system increased by approximately 328 and 152%, respectively. This fog collector provides direction to design water harvesting systems, which has important promotion significance for water collection application engineering in industry, aerospace, and other fields.
ABSTRACT
Lubricant-infused surfaces have attracted widespread attention due to their excellent liquid and organic solution repellency. On account of their high condensation heat transfer coefficient and low nucleation energy barrier, many lubricant-infused surfaces have been applied in water collection. However, they have a number of shortcomings, such as an unstable lubricating layer, poor mechanical/chemical stability and hard shedding, which severely limit the application of slippery surfaces. In this work, the silicone oil was infused into a superhydrophobic monomer (SHM) to form a flexible lubricant-infused monomer (FLIM) with outstanding sliding ability and omniphobicity for low surface energy liquids. Because the silicone oil is similar to the base molecule, there is a strong interacting force to hold the lubricant layer to the surface of the SHM. In addition, the high viscosity of the silicone oil further strengthens the lubricant layer adhesion. Therefore, the FLIM could resist hot liquid and high shear stress (up to 5000 rpm). In addition, the FLIM substrate possessed a self-similar low surface energy structure, which could endure various physical and chemical damages, such as abrasion, scratching, stretching, strong acid and alkali. Finally, pinned droplets could coalesce into large droplets to slide down its surface, resulting from the strain/release due to the high degree of deformation of the surface, which highly enhanced water/liquid coalescence and collection. The preparation of the FLIM was green and the chemicals involved were inexpensive and environmentally friendly, and thus it can be applied for large-scale water collection.
ABSTRACT
As water shortages increase in semi-arid deserts and inland areas, the collection of fog has attracted tremendous attention in recent years. Different types of fog collectors have been widely reported in the past decade. Inspired by the creatures, a micro/nano-structured hybrid hydrophobic-hydrophilic surface was prepared via a simple hydrothermal method. In addition, the Janus performance was obtained using photocatalytic reaction. This hybrid hydrophobic-hydrophilic surface and Janus copper foam integrative system (HB-HL + JCF) may be of research significance because the preparation methods are environmentally friendly and economical. Next, special attention is paid to the systematic physical mechanisms of unidirectional transport and fog collection. In addition to these, the collection process of fog is analyzed in detail, and the optimal conditions for fog collection were selected by changing the sizes and tilt angles of the as-prepared copper foam. Compared to the original copper foam, the HB-HL + JCF exhibits a highly efficient fog collection (about 209% enhancement). Moreover, the experimental results showed that the HB-HL + JCF had excellent stability, and the wettability changes little under long-time ultraviolet light irradiation or multiple heating/cooling cycles. This work may provide insight into the fabrication of new fog harvesting materials and certain reference value for the development of advanced fog collectors for various purposes.
ABSTRACT
It is worth noting that the multifunctional surfaces are highly desirable for water collection applications on droplet nucleation and removal. Although the superhydrophobic surfaces is beneficial to water collection due to easily shed liquid drops and favorable heat-transfer performance, the pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation severely limit the water collection efficiency. Recently, the liquid-infused surfaces have been significant for condensation heat transfer and droplet nucleation but have poor durability. In this work, under the UV light, polydimethylsiloxane was grafted onto ZnO nanorods (through Zn-O-Si bond), and the residual unbonded silicone oil was used as the lubricant, so that it form a hierarchical lubricant-impregnated surfaces. Because of high viscosity of silicone oil and strong intermolecular force between silicone oil and PDMS brush, the lubricant can be firmly fixed in micronanostructure to form a durable lubricant layer. For example, the LISs have outstanding properties such as boiling water repellency, omniphobicity of various liquid, and hot water resistance. Under a self-made hot vapor collection device, the surface can maintain good water collection capacity and there is no obvious change in the lubrication layer. After exposing in sunlight for 7 days and subjecting them to 25 times heating/cooling cycles (heating at 150 °C), the LISs exhibit excellent water collection and repairability. After measurement, the oil content in the water is 43 mg/L, which is harmless to the human body. Through the high-water collection efficiency and durable lubricant layer, the LISs can be applied on a large scale in the water collection industry.
ABSTRACT
Slippery liquid-infused surfaces that imitate the microstructure of carnivorous Nepenthes have attracted widespread attention due to their excellent liquid and various organic solution repellency, associated with broad applications in various fields. However, the complicated preparation processes and poor oil lock ability of slippery liquid-infused surfaces severely restrict their practical application. Herein, lubricant-immobilized slippery surfaces (LISS) were fabricated by grafting polydimethylsiloxane onto ZnO nanorods under ultraviolet light, with residual non-bound silicone oil acting as a lubricant. In addition, the entire reaction is green, and the chemicals involved are inexpensive and environmentally friendly. Moreover, due to the strong intermolecular forces between the non-bound silicone oil and grafted polydimethylsiloxane, silicone oil is firmly locked to the zinc oxide surface, serving as a lubricant layer with a sliding angle of less than 3°. The LISS not only exhibited superior omniphobicity at room-temperature but also retained excellent sliding ability for high-temperature liquids such as hot water and oleic oil. When subjected to a boiling and high temperature test for 15 min, the liquids still slid on the surface with the tilt angles below 4° due to the presence of a uniform lubricant layer. In addition, under extreme operating conditions, such as high shear rate of up to 7000 rpm, long-term immersion for 400 h and strong acid/alkali, the LISS exhibited outstanding slippery stability. Furthermore, its properties of corrosion resistance, anti-icing and anti-fouling are of great significance for extending the practical application of LISS. Therefore, due to their excellent boiling water/hot liquid repellency and long-term slippery stability, the LISS may be promoted on a large scale and are a breakthrough for traditional slippery surface preparation.
