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Water harvesting mechanisms were learnt from smart creatures. The design of bioinspired materials is an effective way of acquiring fresh water from fog. Different biomimetic materials were designed on large-scale real application. Herein, we reviewed recent advances on materials for water harvesting tasks, which are significant for promising applications on the fog collector.

A robust fogwater harvester with an elastic microstaggered porous superhydrophilic framework (EMSF) has been designed. The EMSF can be fabricated by using polydimethylsiloxane and polyvinyl alcohol (PVA) via an etching method of sugar crystals pile-up cube as a template. The EMSF possesses a high porosity of 76%, of which the saturated fogwater-capturing capacity is 4 times higher than its weight, achieving a high fogwater harvesting rate (e) of 62.7 g/cm3·h. It is attributed to the strong hydrogen bond (H-bond) interaction between hydroxyl groups (-OH) in PVA and water molecules for rapidly harvesting water and storing water in a staggered porous structure by means of a capillary force. The elasticity of EMSF allows to achieve a higher fogwater harvesting rate (e) of 73.2 g/cm3·h via releasing the as-stored water in the EMSF under periodic external pressing. In addition, a durable corrosion resistance is demonstrated on the EMSF. This study offers a way to design novel materials that would further be extended into applications, for example, fog engineering in industry, agriculture, forest, and so forth.

Energy level modulation is an effective strategy of increasing the separation efficiency of the photogenerated electrons and holes of sulfide solid solution. In this work, Mn element was introduced to Zn0.5Cd0.5S sulfide solid solution to modulate energy level of photocatalyst. Compared with pure Zn0.5Cd0.5S, Mn-doped Zn0.5Cd0.5S can effectively improve the separation of photogenerated electrons and holes. As a result, the hydrogen production rate of Mn-doped Zn0.5Cd0.5S photocatalyst is 4 and 12 times than that of Zn0.5Cd0.5S and CdS under visible-light irradiation. This improvement of photocatalytic activity of Mn-doped Zn0.5Cd0.5S is attributed to an emerging impurity band, narrow band gap, and negative conduction band after Mn doping. This work provides a rational doping strategy of catalyst and a deep insight of the enhancement mechanism of doping effect for photocatalytic reactions.

Inspired by the densely covered capillary structure inside a dog's nose, we report an artificial nanostructure, i. e., poly(sodium p-styrenesulfonate)-functionalized reduced graphene oxide nanoscrolls (PGNS), with high structural perfection and efficient gas sensing applications. A facile supramolecular assembly is introduced to functionalize graphene with the functional polymer, combined with the lyophilization technique to massively transform the planar graphene-based nanosheets to nanoscrolls. Detailed characterizations reveal that the bioinspired nanoscrolls exhibit a wide-open tubular morphology with uniform dimensions that is structurally distinct from the previously reported ones. The detailed morphologies of the graphene-based nanosheets in each scrolling stage during lyophilization are monitored by cryo-SEM. This unravels an asymmetric polymer-induced graphene scrolling mechanism including the corresponding scrolling process, which is directly presented by molecular dynamics simulations. The fabricated PGNS sensors exhibit superior gas sensing performance with reliable repeatability, excellent linear sensibility, and, especially, an ultrahigh response ( R

In this study, a graphene-based composite 4HQ-rGO/Cu2+ was prepared via the supramolecular assembly of graphene nanosheets with 4-hydroxyquinoline (4HQ) and copper(II) ions. The as-prepared supramolecular assembly exhibited an excellent and enhanced sensing performance towards acetic acid at room-temperature, which was due to the fact that the D–π–A molecules, i.e. 4HQ, were able to accelerate the charge transfer between the graphene nanosheets and 4HQ molecules when acetic acid was attached. In addition, at room temperature, the copper(II) ions also played a critical role as the main active site for gas adsorption, and thus the as-fabricated sensor exhibited a high response, outstanding selectivity, and ultra-fast response/recovery time. To examine the selectivity of the Cu2+ ions for the supramolecular assembly, various other transition metal ions such as Mn2+, Fe3+, Co2+, Ni2+, Cu2+, and Cd2+ were attached to the 4HQ-rGO assembly, and their acetic sensing performance was determined. Interestingly, the supramolecular assembly with the Cu2+ ions (4HQ-rGO/Cu2+) exhibited the best sensing performance compared to other metal ion-based 4HQ-rGO materials. Compared with the typical acetic acid gas sensors reported in the literature, it is noteworthy to mention that the as-prepared 4HQ-rGO/Cu2+ supramolecular assembly exhibited the shortest gas response time (within 5 s) at room temperature. The presented study demonstrates that the as-prepared supramolecular assembly is a promising material as a room temperature acetic acid gas sensor in practical applications.

Inspired by the superwettability peculiarities of cactus spines and pitcher plants, a unique three-dimensional (3D) superhydrophobic liquid-infused (SHBL) frame is designed by both etching nanospines and infusing liquid lubricant into the nanotextures. On the SHBL frame, the liquid-infused interface could effectively capture the tiny droplet and then accelerate the growth, coalescence and transport of the droplet. Moreover, the presence of the nanospines increases the capillary force, which can effectively lock the lubricant on the SHBL frame. Hence, the 3D SHBL frame achieves the high fog harvesting rate (e) of 15.2 g cm-3h−1 and efficiency (η) of 25.3%, and exhibits the excellent cycling stability of the fog harvesting. This study opens up a way to design the novel materials that would be expended into some application realms, e.g., fog/water harvesting engineering in industry, forest, etc.

Heterostructure rough spindle-knot microfibers (HRSFs) are fabricated via a flexible parallel-nozzle microfluidic method. In this method, the bioinspired HRSF with a roughness gradient between spindle-knots and joints, can be manufactured in large-scale, and with which the size of the spindle-knots and joints can be precisely adjusted by regulating flow rates. The HRSFs, fabricated with chitosan and calcium alginate, have strong mechanical properties and corrosion resistance in acid environment (pH = 5) and alkaline environment (pH = 9), respectively. More attractively, under controlled treatment conditions, the morphology of the spindle-knots on the HRSFs can be effectively managed by changing the composite content of calcium chloride in the fluid. During the water collection process, tiny droplets of moisture can be captured on the surface of the HRSFs, subsequently, the droplets can coalesce and be transported from joint to spindle-knot sections. It is demonstrated that the surface morphology of spindle-knots directly influences the water collection efficiency, where a higher roughness gradient generates higher water collection efficiency. This parallel-nozzle microfluidic technology provides a low-cost and flexible method to manufacture high biocompatibility bioinspired rough spindle-knot microfibers, which has many potential applications in large-scale water collection, sustained drug release, and directional water collection.