Self-Repairing Humidity-Adjustable Anisotropic Adhesion Switch for Smart Manipulation.

Stimuli-responsive surface adhesion regulation is widely used in automated assembly systems, intelligent pick-up and placement systems, and soft crawling robots. However, in the actual separation process, it tends to produce separation residue or excessive adhesion. Therefore, how to regulate surface adhesion on demand is a significant challenge. Herein, inspired by the anisotropic adhesion behavior of butterflies and the controlled adhesion behavior of octopuses, based on molecular conformational rearrangement and anisotropic structures, a humidity-responsive PES-PI/PDMS composite surface is achieved to meet the needs of controllable adhesion orientation and strength, which could be used for an intelligent transfer system (grasping and releasing and anisotropic transporting). Humidity can effectively tune the hydrogen bonding and the interaction between polymers, resulting in excellent self-healing and durability properties of the composite surface. Moreover, humidity could adjust the surface transmittance as well, making it possible to be used in humidity sensing and in a detection and encryption/decryption system to enhance environmental monitoring and information protection capabilities. This work not only establishes a method for the fabrication of innovative "high-flexibility" adhesive materials but also provides approaches for the design and development of intelligent response devices.

Curvature Adjustable Liquid Transport on Anisotropic Microstructured Elastic Film.

Directional liquid transport is expected via adjusting chemical components, surface morphology, and external stimuli and is critical for practical applications. Although many studies have been conducted, there are still challenges to achieving real-time transformation of liquid transport direction on the material surface. Herein, we demonstrate a strategy to achieve curvature responsive anisotropic wetting on the elastic film with V-shaped prism microarray (VPM) microstructure, which can be used to control the direction of liquid transport. The results reveal that the curvature change of an elastic film can adjust the arrangement of V-shaped prisms on the elastic film. Correspondingly, the liquid wetting trend will change and even the moving direction reverses with varying arrangements of the V-shaped prisms on the elastic film. Meanwhile, surface hydrophobicity of the VPM elastic film also affects the liquid wetting trend and even shows the opposite transport direction of the liquid, which is up to the water wetting state on the VPM elastic film. Based on these results, the VPM elastic film can serve as a valve to control the liquid transport direction and is promising in the application of liquid directional harvest, chemical reaction, microfluidic, etc.

Ultrastable Super-Hydrophobic Surface with an Ordered Scaly Structure for Decompression and Guiding Liquid Manipulation.

Directional droplet manipulation is very crucial in microfluidics, intelligent liquid management, etc. However, excessive liquid pressure tends to destroy the solid-gas-liquid (SAL) composite interface, creating a highly adhesive surface, which is not conducive to liquid transport. Herein, we propose a strategy to enhance the surface durability, in which the surface cannot withstand liquid pressure only by "blocking" but must instead guide liquid transport for "decompression". Learning from the water resistance of water strider legs and the drag reduction of shark skin, we present a continuous integrated system to obtain an ultrastable super-hydrophobic surface with a highly ordered scaly structure via a liquid flow-induced alignment method for lossless unidirectional liquid transport. The nonwetting scaly structure can both buffer liquid pressure and drive droplet motion to further reduce the vertical pressure of the liquid. Moreover, droplets can be manipulated unidirectionally using a voice. This work could aid in manufacturing scalable anisotropic micro-nanostructure surfaces, which inspires efforts in realizing lossless continuous liquid control on demand and related microfluidic applications.

Gradient monolayered porous membrane for liquid manipulation: from fabrication to application.

The controlled transport of liquid on a smart material surface has important applications in the fields of microreactors, mass and heat transfer, water collection, microfluidic devices and so on. Porous membranes with special wettability have attracted extensive attention due to their unique unidirectional transport behavior, that is, liquid can easily penetrate in one direction while reverse transport is prevented, which shows great potential in functional textiles, fog collection, oil/water separation, sensors, etc. However, many porous membranes are synthesized from multilayer structural materials with poor mechanical properties and are currently prone to delamination, which limits their stability. While a monolayered porous membrane, especially for gradient structure, is an efficient, stable and durable material owing to its good durability and difficult stratification. Therefore, it is of great significance to fabricate a monolayered porous membrane for controllable liquid manipulation. In this minireview, we briefly introduce the classification and fabrication of typical monolayered porous membranes. And the applications of monolayered porous membranes in unidirectional penetration, selective separation and intelligent response are further emphasized and discussed. Finally, the controllable preparation and potential applications of porous membranes are featured and their prospects discussed on the basis of their current development.

Switchable smart porous surface for controllable liquid transportation.

Controllable liquid transportation through a smart porous membrane is realized by manipulating the surface wetting properties and external stimuli, and has been intensively studied. However, the liquid transportation, e.g., permeation and moving process, at the interface is generally uninterrupted, i.e., the opening and closing of the interface is irreversible. Herein, we present a new strategy to achieve magnetic adaptive switchable surfaces, i.e., liquid-infused micro-nanostructured porous composite film surfaces, for controllable liquid transportation, via modulation of the magnetic field. The liquid transportation process can be interrupted and restarted on the porous composite film because its pore structure can be quickly closed and opened owing to the adaptive morphological transformation of the magnetic liquid with a varying magnetic field. That is, the liquid permeation process occurs due to the open pore structure of the composite film when the external magnetic field is added, while the permeation process can be interrupted owing to the self-repairing closure of the pore when the magnetic field is removed, and the moving process can be achieved. Thus a magnetic field induced switchable porous composite film can serve as a valve to control liquid permeation based transportation, which opens new avenues for artificial liquid gating devices for flow, smart separation, and droplet microfluidics.

Stretch-Enhanced Anisotropic Wetting on Transparent Elastomer Film for Controlled Liquid Transport.

Direction-controlled wetting surfaces, special for lubricating oil infused anisotropic surfaces, have attracted great research interest in directional liquid collection, expelling, transfer, and separation. Nonetheless, there are still existing difficulties in achieving directional and continuous liquid transport. Herein, we present a strategy to achieve directional liquid transport on transparent lubricating oil infused elastomer film with V-shaped prisms microarray (VPM). The results reveal that the water wetting direction in the parallel and staggered arrangement of the VPM structure surface with lubricating oil infusion is the opposite, which is completely different from the wetting direction on the usual VPM surface in air. Moreover, asymmetric stretching can enhance or weaken the directional water wetting tendency on the lubricating oil infused VPM elastomer film and even can reverse the droplet wetting direction. In a closed moist environment, tiny droplets gradually coalesce and then slip away from the lubricating oil infused VPM surface to keep the surface transparent, due to the cooperation of imbalanced Laplace pressure, resulting from the anisotropic geometric structures, varying VPMs spacing, and gravity. Thus, this work provides a paradigm to design and fabricate a type of surface engineering material in the application fields of directional expelling, liquid collection, anti-biofouling, anti-icing, drag reduction, anticorrosion, etc.

Meta-analysis of the effect of sodium-glucose cotransporter 2 inhibitors on hepatic fibrosis in patients with type 2 diabetes mellitus complicated with non-alcoholic fatty liver disease.

AIM: This study aimed to analyze the effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors on the indexes of liver fibrosis in patients with type 2 diabetes mellitus complicated with non-alcoholic fatty liver disease, and also to observe the effects on liver enzymes and liver fat. METHODS: This meta-analysis was performed using RevMan 5.3 statistical software. RESULTS: SGLT2 inhibitors could significantly reduce the level of hepatic fibrosis index: fibrosis-4 (mean difference [MD] 0.25, 95% CI -0.39 to -0.11, p = 0.0007); serum type â…£ collagen 7s (MD 0.32, 95% CI -0.59 to -0.04, p = 0.02); and ferritin (MD 26.7, 95% CI 50.64, 2.76, p = 0.03). SGLT2 inhibitors could significantly reduce the level of liver enzymes: alanine aminotransferase (MD 3.49, 95% CI -5.1 to 1.58, p < 0.0001); aspartate aminotransferase (MD 3.64, 95% CI -5.10 to -2.18, p < 0.00001); and glutamate aminotransferase (MD 7.13, 95% CI -12.95 to -1.32, p = 0.02). SGLT2 inhibitors could significantly reduce the level of liver fat: liver-to-spleen attenuation ratio (MD 0.16, 95% CI 0.10-0.22, p < 0.00001); magnetic resonance imaging proton density fat fraction (MD 1.97, 95% CI -3.49 to -0.45, p = 0.01); liver controlled attenuation parameter (MD 0.29, 95% CI -26.95 to -13.64, p < 0.00001); liver fat score (MD 0.55, 95% CI 1.04 to -0.05, p = 0.03); and liver fat index (MD 11.21, 95% CI -16.53 to -5.89, p < 0.0001). CONCLUSION: SGLT2 inhibitors could improve liver fibrosis, liver enzymes, liver fat, and metabolic indexes in patients with type 2 diabetes mellitus complicated with non-alcoholic fatty liver disease.

Molecular-Structure-Induced Under-Liquid Dual Superlyophobic Surfaces.

Surfaces with under-water superoleophobicity or under-oil superhydrophobicity have attractive features due to their widespread applications. However, it is difficult to achieve under-liquid dual superlyophobic surfaces, that is, under-oil superhydrophobicity and under-water superoleophobicity coexistence, due to the thermodynamic contradiction. Herein, we report an approach to obtain the under-liquid dual superlyophobic surface through conformational transitions of surface self-assembled molecules. Preferential exposure of either hydrophobic or hydrophilic moieties of the hydroxythiol (HS(CH2)nOH, where n is the number of methylene groups) self-assembled monolayers to the surrounding solvent (water or oil) can be used to manipulate macroscopic wettability. In water, the surfaces modified with different hydroxythiols exhibit under-water superoleophobicity because of the exposure of hydroxyl groups. In contrast, surface wettability to water is affected by molecular orientation in oil, and the surface transits from under-oil superhydrophilicity to superhydrophobicity when n ≥ 4. This surface design can amplify the molecular-level conformational transition to the change of macroscopic surface wettability. Furthermore, on-demand oil/water separation relying on the under-liquid dual superlyophobicity is successfully demonstrated. This work may be useful in developing the materials with opposite superwettability.

Switchable Wettability and Adhesion of Micro/Nanostructured Elastomer Surface via Electric Field for Dynamic Liquid Droplet Manipulation.

Dynamic control of liquid wetting behavior on smart surfaces has attracted considerable concern owing to their important applications in directional motion, confined wetting and selective separation. Despite much progress in this regard, there still remains challenges in dynamic liquid droplet manipulation with fast response, no loss and anti-contamination. Herein, a strategy to achieve dynamic droplet manipulation and transportation on the electric field adaptive superhydrophobic elastomer surface is demonstrated. The superhydrophobic elastomer surface is fabricated by combining the micro/nanostructured clusters of hydrophobic TiO2 nanoparticles with the elastomer film, on which the micro/nanostructure can be dynamically and reversibly tuned by electric field due to the electric field adaptive deformation of elastomer film. Accordingly, fast and reversible transition of wetting state between Cassie state and Wenzel state and tunable adhesion on the surface via electric field induced morphology transformation can be obtained. Moreover, the motion states of the surface droplets can be controlled dynamically and precisely, such as jumping and pinning, catching and releasing, and controllable liquid transfer without loss and contamination. Thus this work would open the avenue for dynamic liquid manipulation and transportation, and gear up the broad application prospects in liquid transfer, selective separation, anti-fog, anti-ice, microfluidics devices, etc.

Highly Flexible Monolayered Porous Membrane with Superhydrophilicity-Hydrophilicity for Unidirectional Liquid Penetration.

The ability to allow microliquid to penetrate in one direction but block in the opposite direction plays an irreplaceable role in intelligent liquid management. Despite much progress toward facilitating directional transport by multilayer porous membranes with opposite wettability, it remains difficult to achieve a highly multifunctional flexible membrane for highly efficient unidirectional liquid transport in different situations. Herein, a superhydrophilic-hydrophilic self-supported monolayered porous poly(ether sulfone) (PES) membrane with special nano- and micropores at opposite surfaces is demonstrated, which can be used for unidirectional liquid transport. The results reveal that the competition of liquid spreading and permeation is critical to achieve directional liquid transport. The porous PES membrane, transformed with 70 vol % of ethanol in water (E/W-PES-70%), exhibits continuous unidirectional liquid penetration and antigravity unidirectional ascendant in a large range of pH values and can be used as "liquid diode" for moisture wicking. Moreover, the PES membrane can be prepared in a large area with excellent flexibility at room and liquid nitrogen temperature, indicating great promise in harsh environments. This work will provide an avenue for designing porous materials and smart dehumidification materials, which have promising applications in biomedical materials, advanced functional textiles, engineered desiccant materials, etc.

Switchable Direction of Liquid Transport via an Anisotropic Microarray Surface and Thermal Stimuli.

Design and construction of special surface microstructures has made many amazing breakthroughs in directional liquid transport. Despite much progress in this field, challenges still remain in on-demand switchable direction transport of liquid in situ and real-time via transforming the arrangement of the surface microstructure and external stimuli. Herein, we demonstrate a strategy to achieve switchable direction transport of liquid via a tunable anisotropic microarray surface, that is, assembling a V-shaped prism microarray (VPM) surface, which can also be intelligently manipulated by thermal stimuli. By transforming the parallel and staggered prism microstructure arrangement of the VPM, switchable direction transport of a liquid can be successfully achieved on the VPM surface. Flow direction switching among unidirectional transport, bidirectional transport, and reverse unidirectional transport is also achieved on the temperature-adaptive VPM surface by thermal stimuli, which can be used for on-demand liquid transport according to the paths of the microfluidic channels. The work provides a way for precise liquid manipulation in desired liquid transport, which may be utilized in nonpower conveying systems, autolubrication, life fluid medical instruments, and other microfluidic devices.

Multifunctional Magnetocontrollable Superwettable-Microcilia Surface for Directional Droplet Manipulation.

In nature, fluid manipulations are ubiquitous in organisms, and they are crucial for many of their vital activities. Therefore, this process has also attracted widescale research attention. However, despite significant advances in fluid transportation research over the past few decades, it is still hugely challenging to achieve efficient and nondestructive droplet transportation owing to contamination effects and controllability problems in liquid transportation applications. To this end, inspired by the motile microcilia of micro-organisms, the superhydrophobicity of lotus leaves, the underwater superoleophobicity of filefish skin, and pigeons' migration behavior, a novel manipulation strategy is developed for droplets motion. Specifically, herein, a superwettable magnetic microcilia array surface with a structure that is switchable by an external magnetic field is constructed for droplet manipulation. It is found that under external magnetic fields, the superhydrophobic magnetic microcilia array surface can continuously and directionally manipulate the water droplets in air and that the underwater superoleophobic magnetic microcilia array surface can control the oil droplets underwater. This work demonstrates that the nondestructive droplet transportation mechanism can be used for liquid transportation, droplet reactions, and micropipeline transmission, thus opening up an avenue for practical applications of droplet manipulation using intelligent microstructure surfaces.

Identification of microRNAs involved in drought stress responses in early-maturing cotton by high-throughput sequencing.

Drought stress is one of the most important abiotic stresses. Cotton is classified as drought tolerant crop but the regulatory mechanism is unknown. MicroRNAs (miRNAs) have been implicated important roles in stress responses in many plants. However, the study of miRNAs in cotton responsive to drought stress is limited, especially in early-maturing cotton. In this study, we performed deep sequencing of small RNAs to identify known and novel miRNAs involved in the regulation of drought stress and understand the expression profile of miRNAs in early-maturing cotton. Three cotton small RNA libraries: non-stressed Shizao1 (early-maturing cotton variety) library (NSS), drought-stressed Shizao1 library (DSS) and non-stressed Jimian958 (medium-maturing cotton variety) library (NSJ) were constructed for deep sequencing. As a result, we identified a total of 64 known and 67 novel miRNAs in the 3 libraries and 88 of them were dramatically differentially expressed (greater than twofold) during drought stress. In addition, we found the expression of 41 miRNAs increased or reduced more than twofold in early-maturing cotton variety compared with that in medium-maturing cotton variety. Our results significantly increased the number of miRNAs in cotton and revealed for the first time the expression profile of miRNAs for early-maturing cotton.

An Integrated Janus Mesh: Underwater Bubble Antibuoyancy Unidirectional Penetration.

Gas bubbles are a powerful tool with applications in particle visualization, spacers, actuation pistons, and pressure sensors. Controlling the transportation of bubbles in the liquid phase is a challenge that needs to be solved in many industrial processes, such as in the pipe transportation of fluids, the corrosion of ocean vessels, and the control of foaming processes. There are few existing materials capable of the antibuoyancy unidirectional transportation of bubbles. Here, a Janus superwetting mesh is fabricated by integrating aerophilic (AL) and superaerophobic (SAB) surfaces. The resulting composite mesh achieves underwater bubble antibuoyancy unidirectional penetration. In aqueous solution, bubbles pass through the mesh from the SAB side to the AL side, but are blocked from passing through in the opposite direction. This Janus mesh can be considered to be a bubble diode, so is convenient for use in underwater bubble unidirectional transportation. This work may promote the development of advanced materials for gas bubble directional transportation and separation in aqueous media.

External-Field-Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface.

External-field-responsive liquid transport has received extensive research interest owing to its important applications in microfluidic devices, biological medical, liquid printing, separation, and so forth. To realize different levels of liquid transport on surfaces, the balance of the dynamic competing processes of gradient wetting and dewetting should be controlled to achieve good directionality, confined range, and selectivity of liquid wetting. Here, the recent progress in external-field-induced gradient wetting is summarized for controllable liquid transport from movement on the surface to penetration into the surface, particularly for liquid motion on, patterned wetting into, and permeation through films on superwetting surfaces with external field cooperation (e.g., light, electric fields, magnetic fields, temperature, pH, gas, solvent, and their combinations). The selected topics of external-field-induced liquid transport on the different levels of surfaces include directional liquid motion on the surface based on the wettability gradient under an external field, partial entry of a liquid into the surface to achieve patterned surface wettability for printing, and liquid-selective permeation of the film for separation. The future prospects of external-field-responsive liquid transport are also discussed.

Closed Pore Structured NiCo2O4-Coated Nickel Foams for Stable and Effective Oil/Water Separation.

To solve the serious problem caused by oily wastewater pollution, unique interface designs, for example, membranes with superwetting properties such as superhydrophobicity/superoleophilicity and superhydrophilicity/underwater superoleophobicity, provide a good way to achieve oil/water separation. Here, inspired by the liquid storage property of the honeycomb structure, we propose a strategy to fabricate NiCo2O4-coated nickel foams for stable and efficient oil/water separation. NiCo2O4 with a closed-pore structure was formed by assembling nanoflakes with a micro/nanoscale hierarchical structure. Compared with nickel foam coated by NiCo2O4 with an open-pore structure (NiCo2O4 nanowires), the enclosed nanostructure of NiCo2O4 nanoflakes can firmly hold water for a more stable superhydrophilic/underwater superoleophobic interface. As a consequence, the NiCo2O4-nanoflake-coated nickel foam has a larger oil breakthrough pressure than the NiCo2O4-nanowire-coated nickel foam because of a slightly larger oil advancing angle and a lower underwater oil adhesion force, which makes it more stable and efficient for oil/water separation. Moreover, the NiCo2O4-coated nickel foams have excellent chemical and mechanical stability, and they are reusable for oil-water separation. This work will be beneficial for the design and development of stable underwater superoleophobic self-cleaning materials and related device applications, such as oil/water separation.

Fish Gill Inspired Crossflow for Efficient and Continuous Collection of Spilled Oil.

Developing an effective system to clean up large-scale oil spills is of great significance due to their contribution to severe environmental pollution and destruction. Superwetting membranes have been widely studied for oil/water separation. The separation, however, adopts a gravity-driven approach that is inefficient and discontinuous due to quick fouling of the membrane by oil. Herein, inspired by the crossflow filtration behavior in fish gills, we propose a crossflow approach via a hydrophilic, tilted gradient membrane for spilled oil collection. In crossflow collection, as the oil/water flows parallel to the hydrophilic membrane surface, water is gradually filtered through the pores, while oil is repelled, transported, and finally collected for storage. Owing to the selective gating behavior of the water-sealed gradient membrane, the large pores at the bottom with high water flux favor fast water filtration, while the small pores at the top with strong oil repellency allow easy oil transportation. In addition, the gradient membrane exhibits excellent antifouling properties due to the protection of the water layer. Therefore, this bioinspired crossflow approach enables highly efficient and continuous spilled oil collection, which is very promising for the cleanup of large-scale oil spills.

Magnetic field actuated manipulation and transfer of oil droplets on a stable underwater superoleophobic surface.

The transport of fluids at functional interfaces, driven by the external stimuli, is well established. The lossless transport of oil-based fluids under water remains a challenge, however, due to their high stickiness towards the surface. Here, a superhydrophilic and underwater superoleophobic tri-phase water/oil/solid nanoarray surface has been designed and prepared. The unique tri-phase surface exhibits underwater superoleophobic properties with an extremely low stickiness towards oil-based fluids. The magnetic-field-driven manipulation and transport of oil-based magnetic fluids are demonstrated under water, which opens up a new pathway to design flexible and smart devices for the control and transfer of liquid droplets by using tri-phase systems.

Fast Responsive and Controllable Liquid Transport on a Magnetic Fluid/Nanoarray Composite Interface.

Controllable liquid transport on surface is expected to occur by manipulating the gradient of surface tension/Laplace pressure and external stimuli, which has been intensively studied on solid or liquid interface. However, it still faces challenges of slow response rate, and uncontrollable transport speed and direction. Here, we demonstrate fast responsive and controllable liquid transport on a smart magnetic fluid/nanoarray interface, i.e., a composite interface, via modulation of an external magnetic field. The wettability of the composite interface to water instantaneously responds to gradient magnetic field due to the magnetically driven composite interface gradient roughness transition that takes place within a millisecond, which is at least 1 order of magnitude faster than that of other responsive surfaces. A water droplet can follow the motion of the gradient composite interface structure as it responds to the gradient magnetic field motion. Moreover, the water droplet transport direction can be controlled by modulating the motion direction of the gradient magnetic field. The composite interface can be used as a pump for the transport of immiscible liquids and other objects in the microchannel, which suggests a way to design smart interface materials and microfluidic devices.

Underwater self-cleaning scaly fabric membrane for oily water separation.

Oily wastewater is always a threat to biological and human safety, and it is a worldwide challenge to solve the problem of disposing of it. The development of interface science brings hope of solving this serious problem, however. Inspired by the capacity for capturing water of natural fabrics and by the underwater superoleophobic self-cleaning property of fish scales, a strategy is proposed to design and fabricate micro/nanoscale hierarchical-structured fabric membranes with superhydrophilicity and underwater superoleophobicity, by coating scaly titanium oxide nanostructures onto fabric microstructures, which can separate oil/water mixtures efficiently. The microstructures of the fabrics are beneficial for achieving high water-holding capacity of the membranes. More importantly, the special scaly titanium oxide nanostructures are critical for achieving the desired superwetting property toward water of the membranes, which means that air bubbles cannot exist on them in water and there is ultralow underwater-oil adhesion. The cooperative effects of the microscale and nanoscale structures result in the formation of a stable oil/water/solid triphase interface with a robust underwater superoleophobic self-cleaning property. Furthermore, the fabrics are common, commercially cheap, and environmentally friendly materials with flexible but robust mechanical properties, which make the fabric membranes a good candidate for oil/water separation even under strong water flow. This work would also be helpful for developing new underwater superoleophobic self-cleaning materials and related devices.