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Inspired by “Lotus effect” and “Petal effect” from nature, superhydrophobic materials have become a hot spot in recent years. However, the researches on these materials still face great challenges. Herein, the superhydrophobic material with transition between “Lotus effect” and “Petal effect” is fabricated via a facile strategy. In the preparation, the organosilicon polymer acts as the matrix, while modified nano-CaCO₃ (M-CaCO${}_3)$ and hydrophobic nano-SiO₂ (H-SiO${}_2)$ act as the dispersed phase, to construct the superhydrophobic material (OSiP–Ca–Si). Through regulating the ratio of M-CaCO₃ and H-SiO₂, the wetting properties of materials can be controlled for the transition between “Lotus effect” and “Petal effect”. For the materials with different effects, both of the water contact angles (WCAs) are above $150^{\circ }$C, while the slide angles (SAs) are $4^{\circ }$C and $180^{\circ }$C, respectively. The transition mechanism can be explained by the distinct microstructures and the roughness they caused due to the different compositions. It is demonstrated that the material with “Lotus effect” possesses an outstanding self-cleaning function, and the material with “Petal effect” can well be applied in water harvesting. Therefore, this work provides a facile strategy for designing the superhydrophobic material with transition between “Lotus effect” and “Petal effect”, and endows them with different applications, thus exhibiting great significance in the advancement of superhydrophobic materials.

Hydrophilic–hydrophobic hybrid wettability structures, inspired by desert beetles, have been widely designed to enhance the dewdrops’ migration under subcooled or/and high-humidity environment. However, it is still a challenge to regulate the graded distribution of the hydrophilic micro-regions for condensation applications. In this paper, we design a simple spray method to prepare the superamphiphilic–superamphiphobic hybrid wettability coatings by controlling the mass ratio (MR) of superamphiphobic SiO₂ nano-powder and superamphiphilic gypsum micro-powder. We compare the macroscopical wettability, condensation heat transfer efficiency, frosting delayed time and water harvesting rate to demonstrate the unique advantage of hybrid wettability structures. The results show that the condensation heat transfer efficiency, frosting delayed time and water harvesting rate can be respectively promoted to about 131.50% $(\mathrm{\text{MR}}=1\text{:}0.5)$, 134.74% $(\mathrm{\text{MR}}=1\text{:}0.5)$ and 135.62% $(\mathrm{\text{MR}}=1\text{:}1)$, although their macroscopical wettability will gradually reduce with the MR increase. This work will provide substantial insights into the fabrication of efficient superhydrophilic–superhydrophobic hybrid wettability surfaces for condensation heat transfer, anti-frosting and water harvesting applications.

The scarcity of water facing the world is one of the biggest challenges of this century. This challenge requires research plans in the field of water desalination that is not suitable for human use or the harvesting of water from the air. In this work, the performance of the water harvesting unit from the ambient air is studied. For this purpose, a vapor compression system is designed and built, a 372W reciprocating compressor is selected depending on the use of a small family consisting of four persons. The components of the vapor compression system are designed depending on the compressor power. The unit evaporator is modified to condensate the water vapor associated with the air instead of cooling the air. The effect of volume flow rate of air across the evaporator is studied. The range of air volume flow rate is from 224 to 244m³/h, as well as the operation mode of the unit which either continues to condensate or freeze the water vapor on the evaporator is also studied. The result showed that the water harvesting unit can work at a relative humidity as low as about 20%. The maximum water production for the unit is 7.9l/day with a power consumption of 1.76kW-h/l at the volume flow rate of air is 230m³/h. When an evaporative cooler is turned on in the test chamber, the amount of water production increases to about 13.11l/day with a power consumption of 1.068kW-h/l, for the same volume flow rate of air mentioned above.

Sustainable cropping patterns and a systems approach in farming are crucial for the conservation of natural resources and the long-term livelihood of farmers. Achieving agricultural sustainability goals relies on adopting a comprehensive system approach involving developing a comprehensive model for optimal crop and allied enterprise planning. In this study, a multi-objective crop and livestock allocation model (MOCLAM) was devised and evaluated with a case study of the semi-arid and drought-prone Bundelkhand region of Central India. The primary aims of the model were to enhance input efficiency, maximize income and self-sufficiency and minimize water usage and other environmental impacts. The uniqueness of the proposed model lies in three key aspects: First, the model adopts a systemic view of agriculture by simultaneous optimization of both crops and livestock, second, MOCLAM introduces a quasi-dynamic framework and third, the model comprehensively incorporates water considerations from both surface and groundwater sources. The findings of the case study demonstrated that optimal resource allocation can significantly increase farmers’ net economic margins, conserve water and effectively utilize vast monsoon-season (locally termed as kharif) fallow lands in the region. By adopting microirrigation techniques and improved sowing methods, water savings can be more than doubled without compromising economic margins. Compensating farmers for potential lower yields of sesame, a low-water-requiring and stray-cattle-resistant crop, would encourage the adoption of these water-saving practices. Increasing water availability by 24% through water harvesting can boost farmers’ returns by up to 62%. This study suggests that farmers may be reluctant to adopt agroforestry practices, such as integrating trees with field crops, unless they are incentivized for the social benefits these systems provide. It also requires the development of an adequate timber marketing mechanism that is crucial for wider adoption.

The long-standing dream of scientists to be able to link molecules together into crystalline, extended (infinite) 2D and 3D structures is now realized by the establishment of reticular chemistry through the discovery and development of metal-organic frameworks and covalent organic frameworks. The architectural, thermal, and chemical stability of such frameworks allowed study of their ultra-high porosity, reactivity and many applications including carbon capture and conversion to fuels, and water harvesting from desert air.

Addressing the three major stresses facing our planet, clean air, clean energy, and clean water, is within our reach. At present, new materials such as metal-organic frameworks and covalent organic frameworks, produced by reticular chemistry, are at the forefront of efforts to capture carbon dioxide from air and harvest water from air. We envision that the products of these two capture processes (carbon dioxide and water) can be fed into a conversion cycle in which they are used to produce fuels and chemicals via artificial photosynthesis. The use of air as a nonpolluting, cyclable, and sustainable resource for carbon and water can be powered by sunlight. We describe how the scientific basis for realizing this vision is either already achieved or being established, and that in the fullness of time this paradigm may lead to new global industries and a thriving “air economy.”