Difference In Wettability Research Articles

Towards stable sodium metal battery with high voltage output through dual electrolyte design

The application of sodium metal batteries (SMBs) is hindered by the notable challenges of side reactions between electrolyte and Na as well as the growth of Na dendrites. Herein, we report that a unique design of dual electrolytes within double separators, namely lean diglyme-based electrolyte hosted by the polypropylene separator together with sulfolane-based electrolyte hosted by the glass fiber separator (denoted as D-e@PP/S-e@GF), can effectively prevent Na dendrite growth and suppress side reactions. D-e@PP/S-e@GF ingeniously combines the advantages of D-e and S-e by using their wettability difference on separators. Finite element method (FEM) simulations and in-situ optical microscopy reveal that the D-e@PP layer promotes uniform deposition and significantly reduces side reactions. The S-e@GF layer can be paired with high voltage cathodes. D-e@PP/S-e@GF enables a high CE of Na plating/stripping as high as 97.22% over 560 cycles at 0.5 mAh cm−2 and ultra-long cycle life of more than 1900 h at 1 mAh cm−2 in Na||Na symmetric cell. Furthermore, this design also demonstrates excellent cycling stability of full cells using Na3V2(PO4) (NVP) and Prussian Blue (PB) as cathodes. The unique design of dual electrolytes within double separators provides a new and promising avenue to develop high-performance SMBs.

A Direct Writing Approach for Organic Semiconductor Single-Crystal Patterns with Unique Orientation.

Organic semiconductor single-crystal (OSSC) patterns with precisely controlled orientation are of great significance to the integrated fabrication of devices with high and uniform performance. However, it is still challenging to achieve purely oriented OSSC patterns due to the complex nucleation and growth process of OSSCs. Here, a general direct writing approach is presented to readily obtain high-quality OSSC patterns with unique orientation. In specific, a direct writing method is demonstrated wherein the microscale meniscus is manipulated, which makes it possible to precisely control the nucleation and growth process of the OSSC because of its comparable size to the crystal nuclei. The resulting OSSC patterns are highly crystalline and purely oriented, in which each ribbon crystal shows a deviation angle of 33° to the printing direction. The mechanism of orientation purification is revealed experimentally and theoretically, and the results show that the TCL deformation caused by the difference in wettability and adhesive force, as well as the asymmetry of fluid concentration distribution, are the key factors leading to the selective deposition and unique orientation. Moreover, organic field-effect transistors (OFETs) and polarization-sensitive photodetectors are prepared based on the OSSC patterns with unique orientation, which exhibit higher device performance compared to the non-purely oriented crystal-based OFETs.

A Multifunctional Janus Electrospun Nanofiber Dressing with Biofluid Draining, Monitoring, and Antibacterial Properties for Wound Healing.

Wound healing greatly affects patients' health and produces medical burden. Therefore, we developed a multifunctional electrospun nanofiber dressing, which can inhibit methicillin-resistant Staphylococcus aureus (MRSA), drain excessive biofluid to promote wound healing, and simultaneously monitor wound pH level. The polyoxometalate (α-K6P2W18O62·14H2O, P2W18) and oxacillin (OXA) are encapsulated in hydrophobic polylactide (PLA) nanofiber to synergistically inhibit MRSA. The phenol red (PSP) is encapsulated in hydrophilic polyacrylonitrile (PAN) nanofiber to sensitively indicate wound pH in situ. The PSP/PAN nanofiber is directly electrospun on the patterning OXA/P2W18/PLA nanofiber layer to form a Janus dressing. By taking advantage of the wettability difference between the two layers, the excess biofluid can be drained away from the wound. In addition, the Janus dressing exhibits good biocompatibility and accelerates wound healing via its antimicrobial activity and skin repairing function. This multifunctional Janus electrospun nanofiber dressing would be beneficial for wound management and treatment.

Evaporation Patterns of Dextran-Poly(Ethylene Glycol) Droplets with Changes in Wettability and Compatibility.

The dextran–PEG system is one of the most famous systems exhibiting phase separation. Various phase behaviors, including the evaporation process of the dextran–PEG system, have been studied in order to understand the physicochemical mechanism of intracellular phase separation and the effect of condensation on the origin of life. However, there have been few studies in dilute regime. In this study, we focused on such regimes and analyzed the pattern formation by evaporation. The specificity of this regime is the slow onset of phase separation due to low initial concentration, and the separated phases can have contrasting wettability to the substrate as evaporation progresses. When the polymer concentration is rather low (<5 wt%), the dextran–PEG droplets form a phase-separated pattern, consisting of PEG at the center and dextran ring of multiple strings pulling from the ring. This pattern formation is explained from the difference in wettability and compatibility between dextran and PEG upon condensation. At the initial dilute stage, the dextran-rich phase with higher wettability accumulates at the contact line of the droplet to form a ring pattern, and then forms multiple domains due to density fluctuation. The less wettable PEG phase recedes and pulls the dextran domains, causing them to deform into strings. Further condensation leads to phase separation, and the condensed PEG with improved wettability stops receding and prevents a formed circular pattern. These findings suggest that evaporation patterns of polymer blend droplets can be manipulated through changes in wettability and compatibility between polymers due to condensation, thus providing the basis to explore origins of life that are unique to the process of condensate formation from dilute systems.

Superwetting patterned PDMS/PMMA materials by facile one-step electro-spraying for signal expression and liquid transportation

• Patterned PDMS/PMMA coating with asymmetrical wettability has been constructed by electro-spraying technique. • Membrane filters with high wetting contrast demonstrate high separation efficiency and good cycling ability. • Patterned surfaces with anisotropic adhesion show promising on-demand droplet manipulation ability. • Real-time liquid signal expression is realized on such wetting-patterned membrane with high efficiency. Superwetting materials with multiple functions have drawn heightened attention due to their delicately adjustable surface wettability. However, realizing the full potential of diversified functions is often hampered by the usually symmetrical wetting state. Herein, we introduce a versatile electro-spraying technique to construct a patterned PDMS/PMMA coating with asymmetrical wettability. The tunable superwetting patterns are able to achieve the required functional diversity. The as-prepared superhydrophobic fabric can act as a separation filter with a high separation efficiency and satisfactory cycling ability. With the wettability difference, such patterned surfaces can also manipulate the successive drops motions, and relation between the surface patterns and the controllable movement is demonstrated. In addition, the patterned surface can serve as a smart signal-expression membrane, thereby enabling real-time variable liquid signal expression with alterable signals. The exciting results have paved the way for expanding the application foreground of smart superwetting materials in microfluidics and signal-detection.

Fabrication of textured surface with controllable wettability via laser-thermal hybrid processing

Controlling the wettability of metallic surface would be beneficial for many industrial and commercial applications. In this paper, controllable surface wettability was achieved by a facile laser-thermal hybrid processing technique. Either superhydrophobicity or superhydrophilicity was achieved on the laser textured surface through regulating heat treatment temperature. Surface morphology analysis indicated that micro-bumps were created via direct laser texturing with nanoparticles covered on top. In addition, contact angle measurements exhibited the wettability difference for the laser textured surfaces subject to heat treatment at different temperatures. Moreover, surface chemistry was analyzed to elucidate the underlying mechanism for the thermal-induced wettability difference. This study provides a simple and low-cost method for surface wettability control, which is expected to render more practical applications.

Superresolution microscopy of nanotubes and strongly curved membrane segments formed by giant vesicles exposed to molecular condensates

Cell mimetic systems like giant unilamellar vesicles (GUVs) encapsulating macromolecules (polyethylene-glycol and dextran) represent an excellent tool to study membrane transformations associated with molecular crowding and protein condensation. Upon liquid-liquid phase separation as in living cells, these GUVs exhibit highly curved structures such as internal nanotubes and the membrane of GUVs form apparent kinks at the contact line of the interface between the two encapsulated aqueous phases. These membrane structures of high curvature have dimensions below conventional optical resolution and if resolved, can provide quantitative information on membrane spontaneous curvature and the intrinsic contact angle describing the wettability difference of the encapsulated phases to the membrane.

Infiltration characteristics of nanochannels composed of graphene sheets in different directions

The infiltration of water droplets in nanochannels is of great importance in microfluidics. In this paper, two types of graphene nanochannels with different wall structures are constructed based on the experimentally reported graphene structure, and the infiltrations of water nanodroplet in the two nanochannels are investigated by performing all-atom molecular dynamics simulation. It is found that the two nanochannels with the same size, composed of different graphene arrays, exhibit completely different infiltration properties: water droplets cannot infiltrate into the multilayer stacked channels, but can wet the vertical array channels spontaneously and completely. By analyzing the structures of the two nanochannels, the novel phenomenon is mainly attributed to the difference in wettability between the inner surface and the outer surface of the nanochannel. From the perspective of energy, the potential energy of water droplets in the multilayer stacked channels is higher than that outside the channels, while the potential energy of water droplets in the vertical array channels is lower than that outside the channels. Therefore, water droplets can spontaneously infiltrate into the latter ones. The van der Waals interaction between the droplet and the channels and the Coulomb interaction inside the droplet play a dominant role in spontaneously infiltrating the water droplets, while the van der Waals interaction inside the droplet has little effect on the infiltration behavior. In addition, through a series of simulations of water droplets wetting the nanochannels with identical inner surface and outer surface, the wettability phase diagram of water droplets infiltration into nanochannels is established, which represents the general law of water droplet infiltration into nanochannels.

Wettability and Passive Film Difference Investigation of Variant Feedstock Sizes Fe-Based Amorphous Coatings

Wettability and Passive Film Difference Investigation of Variant Feedstock Sizes Fe-Based Amorphous Coatings

Quadruple Anti‐Counterfeiting Retroreflective Structural Color Films

AbstractWhile structural color materials are widely exploited in anti‐counterfeiting applications, it still remains a challenge to develop advanced and multifunctional structural colors for new anti‐counterfeiting technologies. Herein, a novel patterned retroreflective structural color film (PRSCF) with quadruple anti‐counterfeiting capacities is reported based on the changes in iridescent and non‐iridescent colors due to total internal reflection and interference mechanisms, reversible thermal‐responsive patterns owing to the shape memory effect, and reversible decryption and encryption of the patterns due to the surface wettability difference. This quadruple anti‐counterfeiting PRSCF greatly improves the security level and may find important potentials in precious artworks and displays.

Dual Optical Information‐Encrypted/Decrypted Invisible Photonic Patterns based on Controlled Wettability

AbstractInvisible photonic patterns based on responsive photonic crystals show great potential in structural‐color encryption. However, single inherent information (structural color) encryption/decryption means and the incomplete invisibility in normal conditions greatly limit further development in high‐precision encryption. Here, a novel invisible photonic pattern encrypted/decrypted by dual optical information (structural color and brightness) is reported. It is prepared by engineering an extremely large wettability difference into the patterned and unpatterned regions of a vapor‐responsive inverse opal film. The same optical properties and the distinct wettability difference between the two regions not only ensure that the pattern encrypted by structural color and brightness in the normal state can be entirely hidden under the microscope, but also ensure that it can be decoded by large color contrast (Δλ = 26–32 nm) and brightness contrast (ΔB = 48–57.6) under flowing water vapor state. The unique invisible photonic pattern, reported for the first time, can inject new life into structural color‐based encryption.

Recycling of electrode materials from spent lithium-ion battery by pyrolysis-assisted flotation

In this study, the flotation technology is used for the separation and purification of cathode and anode material after removing organics by pyrolysis. Effects of surface microscopic properties on the flotation efficiency of spent electrode materials are investigated, and on this basis, surface analysis combined with flotation foundation tests are conducted to reveal pyrolysis-assisted surface modification mechanism. Residual electrolyte and organic binders decrease the difference in wettability of cathode and anode material, and hinder the interaction between electrode particles and collecting agent. Organics and their pyrolysis products can be adequately removed at the optimum pyrolysis temperature of 550 °C. After pyrolysis, the change of Zeta potential and surface free energy demonstrates that hydrophilic components of cathode material increase while the hydrophobic components of the anode material increase. The induction time of cathode material rises from 190 ms to 650 ms while the induction time of the anode material decrease from 145 ms to 37 ms. Collector adsorption capacity of anode material is obviously improved and anode material is easy to incorporate with bubbles and will be collected in the froth product. After one stage flotation, the recovery rate of cathode material is 83.75% with a high grade of 94.72%.

Multifuctional Janus Materials for Rapid One-Way Water Transportation and Fog Collection.

A novel micronano wire channels Janus membrane (WCJM) was fabricated by a convenience spraying method. We prepared a series of samples with different (super)hydrophobic energy barriers and studied the effects of WCJMs on one-way transportation and fog collection. The droplets can be one-way transported from the (super)hydrophobic side to the superhydrophilic side, forming a transport channel when they contact the superhydrophilic micronano wire under hydrostatic pressure. In the experiment, when droplets touch the exposed micronano wires, they will be rapidly absorbed by the superhydrophilic side. However, when the superhydrophobic energy barrier is thick and the superhydrophobic layer completely covers the micronano wires on the substrate surface, the droplets cannot achieve one way transport behavior. Besides, we observed three different fog collection modes. They have a significant difference in fog collection efficiency. In WCJM-3, the superhydrophobic side collects fog in a dropwise condensation mode, and then transported to the superhydrophilic side through the micronano wire channels for storage, with the highest fog collection efficiency (1.1 g/cm2·h). The results show that the WCJM surface not only makes full use of the difference in wettability and micronano wire structure to promote the droplets one-way transportation, but also improves the fog collection performance by accelerating surface regeneration, which has potential application value in fog collection, droplet treatment and related engineering.

EFFECT OF CHITOSAN FILM SURFACE STRUCTURE ON THE CONTACT ANGLE

The aim of this study was to evaluate the influence of the surface microstructure of chitosan films on the contact angle. Films without plasticising additives made of chitosan or regenerated chitosan were selected for the tests. A sessile drop method based on the European Pharmacopoeia was used to determine the contact angle. Due to the method of film production, the contact angle measurements were made on both the top and bottom surfaces of the film. For chitosan or regenerated chitosan films, the method of preparation slightly affected the difference in wettability between the top and bottom of the films, as confirmed by scanning electron microscopy. On the other hand, the wettability of the top and bottom of cellulose films varied greatly depending on the side of the film. Both chitosan and cellulose films had a homogeneous structure. There were differences in the microstructure between the top and the bottom of the sample in the cellulose film, a factor that affected the contact angle and thus the wettability of the surface.

Relationship between structure and some physico-chemical properties of funori from red seaweed Gloiopeltis

The relationship between structural characteristics and some physico-chemical properties of ma-funori and fukuro-funori was elucidated. Ma-funori and fukuro-funori were extracted from red seaweeds which was harvested in Japan. The structure of ma-funori and fukuro-funori extracted from Gloiopeltis tenax and Gloiopeltis furcata , respectively, was characterized through FT-IR and NMR spectroscopy. The assignment of signals for ma-funori showed that structure of ma-funori was relatively regular with repeating unit (1,3)-β- D -galactopyranose 6-sulfated linking to (1,4)-3,6-anhydro-α- L -galactopyranose. In contrast, the structure of fukuro-funori was complex with substitute groups such as pyruvate acetal, sulfate ester and methyl ether groups interspersing in polysaccharide chain. The physico-chemical properties of two kinds of funori which are important to restoration and conservation of artistic heritage were characterized. The solubility of fukuro-funori in water was higher than that of ma-funori. The wettability of fukuro-funori solution was better than that of ma-funori solution, whereas ma-funori solution was higher in viscosity than fukuro-funori. The structural characteristic was the main factor to determine the difference in solubility, wettability, and viscosity of two kinds of funori.

Rheology of Immiscible Two-phase Flow in Mixed Wet Porous Media: Dynamic Pore Network Model and Capillary Fiber Bundle Model Results

Immiscible two-phase flow in porous media with mixed wet conditions was examined using a capillary fiber bundle model, which is analytically solvable, and a dynamic pore network model. The mixed wettability was implemented in the models by allowing each tube or link to have a different wetting angle chosen randomly from a given distribution. Both models showed that mixed wettability can have significant influence on the rheology in terms of the dependence of the global volumetric flow rate on the global pressure drop. In the capillary fiber bundle model, for small pressure drops when only a small fraction of the tubes were open, it was found that the volumetric flow rate depended on the excess pressure drop as a power law with an exponent equal to 3/2 or 2 depending on the minimum pressure drop necessary for flow. When all the tubes were open due to a high pressure drop, the volumetric flow rate depended linearly on the pressure drop, independent of the wettability. In the transition region in between where most of the tubes opened, the volumetric flow depended more sensitively on the wetting angle distribution function and was in general not a simple power law. The dynamic pore network model results also showed a linear dependence of the flow rate on the pressure drop when the pressure drop is large. However, out of this limit the dynamic pore network model demonstrated a more complicated behavior that depended on the mixed wettability condition and the saturation. In particular, the exponent relating volumetric flow rate to the excess pressure drop could take on values anywhere between 1.0 and 1.8. The values of the exponent were highest for saturations approaching 0.5, also, the exponent generally increased when the difference in wettability of the two fluids were larger and when this difference was present for a larger fraction of the porous network.

Wettability of complex Long-Chain alkanes droplets on Pillar-type surfaces

To reveal the difference in wettability of long-chain alkane and simple molecular materials on the structural surfaces, we employ long-time molecular dynamics simulation to study the wettability of complex alkane droplets on flat and pillar-type surfaces by comparing the contact angle and the transition of the wetting state. The results showed that the transition of the wetting state depended on the joint action of potential coefficient, pillar spacing, and pillar height, and the wetting state of droplets could transform into each other among Wenzel state, Cross state, and Cassie state. The accurate ranges of the predicted values of the Cassie formula were the weaker fluid–solid attraction and smaller pillar spacing. In contrast, the accurate ranges of the predicted values of the Wenzel formula were the stronger fluid–solid attraction and smaller roughness. When the fluid–solid attraction was strong and the pillar spacing was small, both the Wenzel and Cassie formula could accurately predict the corresponding contact angle. By giving the corresponding conditions of the Cross state and revealing the differences in alkane droplets with variable chain lengths in the transition of the wetting state, it could serve as a reliable reference for subsequent simulations of complex materials on nanostructure surfaces.

Wettability Difference Induced Out-of-Plane Unidirectional Droplet Transport for Efficient Fog Harvesting.

Securing freshwater resources is a global issue for ensuring sustainable development. Fog harvesting is attracting great attention as a method to collect water without any energy input. Previous reports that were inspired by insects and plants have given insights such as the effectiveness of in-plane wettability and structural differences for droplet transport, which might enhance artificial water harvesting efficiency. However, further efforts to transfer droplets while maintaining performance are needed because droplet motion owing to these effects is limited to the in-plane direction. In this study, we report droplet transport between three-dimensional copper wire structures with nanostructured hydrophobic and superhydrophilic features. This mechanism enhanced the fog harvesting capability by more than 20% compared with the cumulative value of individual wires. In addition, the relationship between the droplet height and spacing of wires affected the performance. Our results show the importance of out-of-plane directional droplet transport from the wire surface assisted by differences in wire wettability, which minimizes limiting factors of fog harvesting including clogging and droplet shedding. Furthermore, the proposed arrangement reduces the overall system width compared with that of a two-dimensional arrangement while maintaining the amount of harvested water. These results provide a promising approach to designing large-scale and highly efficient fog harvesters.

SERS substrate with wettability difference for molecular self-concentrating detection

The surface-enhanced Raman spectroscopy (SERS) has attracted much attention due to the powerful capability of quantificational analysis. Nowadays, most of the enhancement effect by SERS substrate is provided by the ‘hot spots’ occupying relatively small space. When the amount of analyte is too low, it is difficult to ensure that all the probe molecules can be placed into the ‘hot spots’, which is a headache in SERS quatification. In order to solve this problem, we have developed a structure of CuO nanowires/Ag nanoparticles with wettability capacity difference, which can aggregate molecules in water and oil simultaneously under two different mechanisms. The limit of detection and enhancement factor of this structure are estimated as 10−15 M and 1.55 × 1011 respectively (for rhodamine 6G, R6G). In a proof-in-principle experiment of sewage detection, it successfully achieved the aggregation and additional enhancement of both the R6G molecules in aqueous solution and thiuram molecules in toluene, realizing efficient and accurate Raman detection.

Femtosecond and picosecond laser fabrication for long-term superhydrophilic metal surfaces

This paper reports the femtosecond (fs) laser and picosecond (ps) laser fabrications to create superhydrophilic surfaces. Subsequently, investigations of the surface morphologies and the surface chemistry using EDS, XRD, and FTIR-spectroscopy are carried out. Due to significant variations in the formation of micro-nano structure and molecular compositions, fs laser and ps laser fabricated surfaces exhibited a noteworthy difference in surface wettability by controlling the laser parameters. It is evident from experimental results that ps laser structured surfaces show efficient superhydrophilic nature (0° contact angle with 300 ± 18 ms spreading time) than the fs laser (0° contact angle with 400 ± 18 ms spreading time) due to higher surface roughness factor and surface energy resulted from laser-induced thermalization. Nevertheless, all fabricated surfaces convert from superhydrophilic to superhydrophobic due to chemisorbed hydroxyl (–OH) and C–C(H) functional group contamination. An eco-friendly zeolite (Na-based ZSM-5) coating is used on such ultrafast laser fabricated surfaces to maintain the superhydrophilic property for more than 14 months. The proposed investigation provides an innovative approach for producing long-term stable superhydrophilic metal surfaces, which are useful for water treatment, microfluidics, and heat transfer applications.