Design and construction of a Laplace and wettability gradient field for efficient water collection.

A hydrophilic-hydrophobic hybrid surface with a vein-like pattern was prepared on a copper substrate using 3D printing technology and laser scanning technology. Under the action of the Laplace pressure gradient and wettability gradient, the superhydrophilic (SHL) vein-like pattern on the superhydrophobic (SHB) surface aided the directional transport of water droplets. The presented scheme combined with the wettability and surface pattern could achieve a water-collection efficiency of 4258.59 mg cm-2 h-1.

Mussel-Inspired Robust Peony-like Cu3(PO4)2 Composite Switchable Superhydrophobic Surfaces for Bidirectional Efficient Oil/Water Separation.

To alleviate the economic and environmental damage caused by industrial discharges of oily wastewater, materials applied for efficient oil/water separation are receiving significant attention from researchers and engineers. Among others, switchable wettable materials for bidirectional oil/water separation show great potential for practical applications. Inspired by mussels, we utilized a simple immersion method to construct a polydopamine (PDA) coating on a peony-like copper phosphate surface. Then, TiO2 was deposited on the PDA coating surface to build a micro-nano hierarchical structure, which was modified with octadecanethiol (ODT) to obtain a switchable wettable peony-like superhydrophobic surface. The water contact angle of the obtained superhydrophobic surface reached 153.5°, and the separation efficiency was as high as 99.84% with a flux greater than 15,100 L/(m2·h) after 10 separation cycles for a variety of heavy oil/water mixtures. Notably, the modified membranes have a unique photoresponsiveness, transforming to superhydrophilic upon ultraviolet irradiation, achieving separation efficiencies of up to 99.83% and separation fluxes greater than 32,200 L/(m2·h) after 10 separation cycles for a variety of light oil/water mixtures. More importantly, this switch behavior is reversible, and the high hydrophobicity can be restored after heating to achieve efficient separation of heavy oil/water mixtures. In addition, the prepared membranes can maintain high hydrophobicity under acid-base conditions and after 30 sandpaper abrasion cycles, and damaged membranes can be restored to superhydrophobicity after a brief modification in the ODT solution. This simple-to-prepare, easy-to-repair, robust membrane with switchable wettability shows great potential in the field of oil/water separation.

Tinware-Inspired Aerobic Surface-Initiated Controlled Radical Polymerization (SI-Sn0CRP) for Biocompatible Surface Engineering.

Surface anchored polymer brushes prepared by surface-initiated controlled radical polymerization (SI-CRP) have raised considerable interest in biomaterials and bioengineering. However, undesired residues of noxious transition metal catalysts critically restrain their widespread biomedical applications. Herein, we present a robust and biocompatible surface-initiated controlled radical polymerization catalyzed by a Sn(0) sheet (SI-Sn0CRP) under ambient conditions. Through this approach, microliter volumes of vinyl monomers with diverse functions (heterocyclic, ionic, hydrophilic, and hydrophobic) could be efficiently converted to homogeneous polymer brushes. The excellent controllability of SI-Sn0CRP strategy is further demonstrated by the exquisite fabrication of predetermined block and patterned polymer brushes through chain extension and photolithography, respectively. Additionally, in virtue of intrinsic biocompatibility of Sn, the resultant polymer brushes present transcendent affinity toward blood and cell, in marked contrast to those of copper-based approaches. This strategy could provide an avenue for the controllable fabrication of biocompatible polymer brushes toward biological applications.

Transport and collection of water droplets interacting with bioinspired fibers.

Inspired by natural creatures, such as spider silk, scientists have designed various bionic materials with special wettability. Compared with two-dimensional and three-dimensional materials, one-dimensional materials, such as fiber, with special wettability can dynamically transport or manipulate liquid droplets, attracting widespread attention. This paper reviews the latest developments of bioinspired fibers in the directional steering and transportation of droplets. Firstly, some fundamental theories of droplet's directional motion are reviewed. The movement of liquid droplets on the fiber is usually affected by several factors/features of the artificial fibers. Then the advantages and disadvantages of four representative methods for preparing bioinspired fibers with different features are reviewed. Subsequently, this paper continues to analyze the influencing factors of bioinspired fibers for efficient water collection and droplet driving direction, and the advantages of different structural combinations. Specifically, a section was dedicated to discuss droplets detachment from fibers. Finally, we provide some improved ideas and outlooks for developing of one-dimensional bioinspired fibers.

Bioinspired surfaces with special micro-structures and wettability for drag reduction: which surface design will be a better choice?

Human beings learn from creatures in nature and imitate them to solve challenges in daily life. Thus, the use of bioinspired surfaces for drag reduction has attracted extensive attention in recent years due to their important applications in many fields, such as pipeline systems, maritime transportation, and military weapons. Herein, we introduce some typical plants and animals with low drag surfaces that exist in nature, focusing on their drag reduction patterns. There are two main mechanisms to explain how surfaces reduce frictional drag, where one is to design a suitable surface geometry to change the flow distribution of surrounding fluid and the other is to introduce a low friction lubricating layer (usually air or non-toxic silicone oil) to partially or completely replace the solid-liquid interface. Hence, by mimicking these organisms, some surfaces have been fabricated to reduce frictional drag, including riblets, superhydrophobic surfaces, and slippery liquid-infused porous surfaces. With the increasing research on drag-reducing surfaces, the drag reduction rate of different types of surface designs has greatly improved in recent years. This review provides a holistic overview that facilitates direct comparisons between these surface types. To select an optimal surface for drag reduction in practical applications, the merits and deficiencies of different surface designs are analysed and compared. Finally, based on the current challenges, we present some future prospects for the application of bioinspired surfaces in drag reduction.

New insights into unusual droplets: from mediating the wettability to manipulating the locomotion modes.

The ability to manipulate droplets can be utilized to develop various smart sensors or actuators, endowing them with fascinating applications for drug delivery, detection of target analytes, environmental monitoring, intelligent control, and so on. However, the stimuli-responsive superhydrophobic/superhydrophilic materials for normal water droplets cannot satisfy the requirements from some certain circumstances, i.e., liquid lenses and biosensors (detection of various additives in water/blood droplets). Stimuli-responsive wetting/dewetting behaviors of exceptional droplets are open issues and are attracting much attention from across the world. In this perspective article, the unconventional droplets are divided into three categories: ionic or surfactant additives in water droplets, oil droplets, and bubble droplets. We first introduce several classical wettability models of droplets and some methods to achieve wettability transition. The unusual droplet motion is also introduced in detail. There are four main types of locomotion modes, which are vertical rebound motion, lateral motion, self-propulsion motion, and anisotropic wettability controlled sliding behavior. The driving mechanism for the droplet motion is briefly introduced as well. Some approaches to achieve this manipulation goal, such as light irradiation, electronic, magnetic, acid-base, thermal, and mechanical ways will be taken into consideration. Finally, the current researches on unconventional droplets extending to polymer droplets and liquid metal droplets on the surface of special wettability materials are summarized and the prospect of unconventional droplet research directions in the field of on-demand transport application will be proposed.

Integration of bubble phobicity, gas sensing and friction alleviation into a versatile MoS2/SnO2/CNF heterostructure by an impressive, simple and effective method.

The engineering of composite surfaces and interfaces of materials at the micro/nano-hierarchical level with multiple functionalities is attracting increasing attention due to their biomimetic technological applications, especially the self-cleaning with gas bubbles, gas sensing and sustainable anti-friction performances. Herein, the ternary MoS2/SnO2/CNF (CNF: carbon nanofiber) was designed and assembled by an in situ facile method. Interestingly, its microstructure exhibits a necklace-like morphology. The MoS2/SnO2/CNF shows desirable bubble phobicity under water and in a PAO4 environment on various substrates, an acceptable gas-sensing ability to target gas with a detection limit of 5 ppm and fascinating tribological performances for additives in different kinds of base/lubricating oils. These results demonstrate that the necklace-like ternary MoS2/SnO2/CNF structure could have numerous applications in one system and may provide a new perspective in composite surface and interface materials engineering.

Bionic smart recycled paper endowed with amphiphobic, photochromic, and UV rewritable properties.

The single-use of large volumes of paper has become a serious issue which is depleting our resources and damaging the environment. It is of great significance and challenging to adopt simple, reasonable and practical methods to prepare functional recyclable paper. In this article, inspired by pleochromatic creatures and plant leaves' special wettability, a series of photochromic amphiphobic recycled paper (PAR i ) products was successfully prepared by adding gourd-like modified tungsten trioxide (MTT) to waste paper pulp. The results show that PAR2-7 has excellent lyophobic performance and amazing photochromic properties. It is worth noting that PAR7 has an impressive amphiphobic behavior, and its surface water contact angle (WCA) and oil contact angle (OCA) are 146 ± 1° and 137 ± 1°, respectively. It can withstand continuous ultraviolet light irradiation for 60 h, indicating excellent resistance to ultraviolet radiation. Most importantly, the reversible photochromic properties of PAR7 make it possible to write repeatedly on the surface by using ultraviolet light. In short, the performance of the prepared PAR is stable and superior, which can not only alleviate paper waste, but also means it has great potential in the fields of decoration, packaging, and banknote anti-counterfeiting technology.

The highly-efficient light-emitting diodes based on transition metal dichalcogenides: from architecture to performance.

Transition metal dichalcogenides (TMDCs) with layered architecture and excellent optoelectronic properties have been a hot spot for light-emitting diodes (LED). However, the light-emitting efficiency of TMDC LEDs is still low due to the large size limit of TMDC flakes and the inefficient device architecture. First and foremost, to develop the highly-efficient and reliable few-layer TMDC LEDs, the modulation of the electronic properties of TMDCs and TMDC heterostructures is necessary. In order to create efficient TMDC LEDs with prominent performance, an in-depth understanding of the working mechanism is needed. Besides conventional structures, the electric (or ionic liquid)-induced p-n junction of TMDCs is a useful configuration for multifunctional LED applications. The significant performances are contrasted in the four aspects of color, polarity, and external quantum efficiency. The color of light ranging from infrared to visible light can be acquired from TMDC LEDs by purposeful and selective architecture construction. To date, the maximum of the external quantum efficiency achieved by TMDC LEDs is 12%. In the demand for performance, the material and configuration of the nano device can be chosen according to this review. Moreover, novel electroluminescence devices involving single-photon emitters and alternative pulsed light emitters can expand their application scope. In this review, we provide an overview of the significant investigations that have provided a wealth of detailed information on TMDC electroluminescence devices at the molecular level.

Characteristics of binary WO3@CuO and ternary WO3@PDA@CuO based on impressive sensing acetone odor.

A series of biomimetic electronic nose nanomaterials of WO3, WO3@PDA, WO3@PDA@CuO, WO3@CuO and CuO were prepared by a facile method and their microstructures, surface chemical composition and sensing ability for acetone odor were investigated systematically by a variety of technologies. The WO3@PDA@CuO and WO3@CuO particles are in nano-sized shape, about 20 nm. The sensing ability to different concentrations acetone odor (50, 100 and 200 ppm) is addressed. The effect of different sensitivity definitions (Rg/Ra or |Ra - Rg|/Ra × 100%) on the comparison of experiment results is discussed. The WO3@CuO sensing material shows the best sensing performance of all the sensors, being independent of concentration or sensitivity definitions. These results provide novel insights into the design and preparation of composite electronic nose sensing nanomaterials.

Stable Janus superhydrophilic/hydrophobic nickel foam for directional water transport.

Janus superhydrophilic/hydrophobic macroporous nickel foam for directional water transport has been demonstrated via a simple floating strategy. Water can transport from hydrophobic to superhydrophilic layer through Janus nickel foam, but cannot transfer from superhydrophilic to hydrophobic layer. This "3D water diode" Janus nickel foam shows extremely high transport rate and outstanding stability. After damaged by abrasion, its directional water transport property retains well.

Bio-inspired one-pot route to prepare robust and repairable micro-nanoscale superhydrophobic coatings.

Superhydrophobic (SHP) coatings inspired by lotus have great application prospect for our daily life. Regrettably, three formidable challenges, namely, complex fabrication, weak mechanical stability and large-scale fabrication, have already existed for a long time in this research field. Here, a robust micro-nanoscale P25 (Nano TiO2)/MgO/epoxy resin (ER) SHP coating has been fabricated via facile one-pot route, which can be applied to arbitrary substrates through multiples methods. P25/MgO/ER SHP coating not only displays excellent mechanical stability but also shows unique repairable ability to recover its superhydrophobicity under various damages by extreme environment such as low temperature, strong acid or alkali and this repairable process can be repeated for many times. P25/MgO/ER SHP coating also is easy to large-scale fabrication with very low cost.

Green fabrication of coloured superhydrophobic paper from native cotton cellulose.

Paper is kind of essential materials in our daily life. However, it can be easily destroyed by water owing to its superhydrophilic surface. Here, we reported a simple and green fabrication of coloured superhydrophobic paper via swelling and approximate dissolution of cotton followed by precipitation of cellulose and doping coloured stearates. The obtained paper exhibited uniform colour and superhydrophobicity, of which the colour was consistent with the doped stearates owing to the adhesion of stearate powders to the tiny floc fiber surface and we proved that the superhydrophobicity could not be damaged after abrasion resulting from the inner and outer superhydrophobicity and the increased surface roughness. This coloured superhydrophobic paper would be avoided from moisture damage and may be useful in different fields.

High-efficiency water collection on biomimetic material with superwettable patterns.

A superhydrophilic surface with two superhydrophobic circular patterns was fabricated via a simple and rapid route, showing outstanding fog harvesting properties with a water collection rate (WCR) of 1316.9 mg h-1 cm-2. Water collection can be repeated on the sample 10 times without obvious change in the WCR.

Hybrid MWCNTs membrane with well-tunable wettability.

With the development of surface science, surface with special wettability, such as reversible or gradient, gradually becomes the focus of the field of science now. Here, via a facile, green organic solvent-free route, we have fabricated superhydrophobic hybrid MWCNTs membrane on mixed cellulose ester filter with great flexibility and tailorability. Importantly, induced by acetic acid vapour and NH3 vapour without external energy, wettability of it can be reversibly switched between superhydrophobic (low adhesion) to hydrophobic (high adhesion). Furthermore, hybrid MWCNTs membrane can achieve diverse range of gradient wettability. The principle of theory behind phenomenon also has been explained through surface chemical composition and microscopic surface topography by means of Field-emission scanning electron microscope (FESEM) images, X-ray photoelectron spectroscopy (XPS) and Fourier transformer infrared spectra (FTIR) spectroscopy. This work has solved some critical problems in this field. The limitations and potential application of our work also be summarized.

Engineering NiO sensitive materials and its ultra-selective detection of benzaldehyde.

Ongoing interest in oxide semiconductor as components of gas sensing devices is motivated by environmental monitoring and intelligent control. NiO with different precursor solution were synthesized by aqueous chemical deposition and pyrolysis process. Here the method is quite facile, green and free of surfactant. Their morphology, crystal structure and chemical composition have been systemically characterized by various techniques. Interestingly, the microstructures of NiO can be engineered by different nickel salt (nitrate or chloride). These NiO based gas sensors showed substantially enhanced responses to benzaldehyde target analyte and exhibited fast response-recover feature. The observed gas sensing behavior is explained in terms of oxygen ionosorption mechanism.

Tuning SnO2 architectures with unitary or composite microstructure for the application of gas sensors.

Different SnO2 architectures with unitary or binary structure were successfully assembled utilizing the assistance of Polyvinyl pyrrolidone (PVP). The microstructure, surface topography, specific surface area and gas sensing property were investigated with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) and WS-60A gas sensing apparatus, respectively. The sensing amplitude, selectivity, response time and recovery time were carefully studied. The possible mechanism of crystallization and gas sensing behavior were also discussed. The present study could be potentially applied to the ethanol or acetone detection and referenced by other researchers and engineers.

Fabrication of stable and durable superhydrophobic surface on copper substrates for oil-water separation and ice-over delay.

We report a simple and rapid method to fabricate superhydrophobic films on copper substrates via Fe(3+) etching and octadecanethiol (ODT) modification. The etching process can be as short as 5 min and the ODT treatment only takes several seconds. In addition, the whole process is quite flexible in reaction time. The superhydrophobicity of as-prepared surfaces is mechanically durable and chemically stable, which have great performance in oil-water separation and ice-over resistance.

Comparison of the enhanced gas sensing properties of tin dioxide samples doped with different catalytic transition elements.

In this work, non-doped SnO2 samples, and SnO2 samples doped with Zn(II), Cu(II), or Mn(II), having hierarchical microstructures, were prepared using an otherwise identical hydrothermal process, followed by annealing. The morphological and structural characteristics of the samples were systematically characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS). Ten gas sensors were constructed from each material, and compared as to detection of gas-phase ethanol, acetone, glacial acetic acid, methanol, and ammonia. The results indicated, for example, that SnO2 containing 2.91% Mn dopant exhibited a 2.5-fold higher gas detection response toward ethanol at 100 ppm than that of the non-doped material. The fastest response time for 100 ppm ethanol was found for Cu(II)-doped SnO2 (9.7 s), compared with 12.4 s for non-doped SnO2. Graphs of sensor response versus operating temperature for SnO2 containing different types and quantities of dopant exhibited quite different morphologies. The gas-sensing mechanism appears to involve reactions between the detected gases and the various oxygenous ions, such as O, O2(-), and O(2-), present at the surface of the sensor.