Study on the surface energy of graphene by contact angle measurements

Correlation of surface properties with dissolution behavior of amorphous solid dispersion of Riluzole and its pharmacodynamic evaluation

Formulation of amorphous solid dispersion (ASD) of any poorly water-soluble drug is among the most promising techniques to increase the dissolution profile of drug and hence its bioavailability. Various literatures give evidences of the role of drug-polymer interactions in the ASD systems, very little information is available about the surface properties of the drug molecule and their ASDs which contributes to a higher dissolution profile. Current work focuses on exploring the surface behavior of a poorly water-soluble drug Riluzole (RLZ) and its ASDs prepared with two highly hydrophilic polymers, polyacrylic acid (PAA), and polyvinylpyrrolidone vinyl acetate (PVP VA). Initial characterization using X-ray diffraction (XRD) revealed about the weight fraction of drug required to prepare a single-phase homogenous system with both the polymers. The saturation solubility and the dissolution studies showed an increase in RLZ solubility as well as the dissolution profile due to the presence of polymers. The role of polymers in changing the surface properties in terms of wettability and polarity were explored using contact angle method and X-ray photon spectroscopy (XPS). Additionally, the neuroprotective efficacy and dose dependent hepatotoxicity were also evaluated in male wistar rats. These studies confirmed the increase in the surface polarity and hence the enhanced ability of ASD formulations to interact with water. The in vivo studies indicated that at the current recommended dose the efficacy as well as toxicity is increased for the ASD formulation. Hence, this formulation can be given at a lower dose to achieve same therapeutic effect with lower toxicity.

Enhancing biofilm resistance and preserving optical translucency of 3D printed clear aligners through carboxybetaine-copolymer surface treatment

OBJECTIVES

This study aimed to use a carboxybetaine methacrylate (CBMA) copolymer solution to surface treat 3D printed clear aligners at different fabrication stages, to impart antifouling properties, and assess the surface treatment at various fabrication stages' impact on physico-mechanical characteristics.

METHODS

Surface treatments using a blend of 2-hydroxyethyl methacrylate (HEMA) and CBMA, termed CCS, were performed at various stages of 3D printed clear aligner fabrication. Experimental groups, CB1, CB2, and CB3, were determined by the stage of surface treatment during post-processing. CB1, CB2, and CB3 received treatment before post-curing, after post-curing, and after post-processing, respectively. Untreated samples served as controls. Physical and mechanical properties were assessed through tensile testing, Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and UV-Vis spectroscopy. The surface was further characterized through scanning electron microscopy and contact angle measurements. The cytotoxicity was assessed with 7-day elution and agar diffusion assays. Lastly, bacterial biofilm resistance was evaluated using confocal laser scanning microscopy. Crystal violet assay was performed using Streptococcus mutans.

RESULTS

Surface treatment during CB1 stage exerted the most significantly unfavorable influence on properties of the 3D printed aligner resin. CB2 samples showed the maximum preservation of translucency even after 7-day aging. CB2 and CB3 phases showed enhanced hydrophilicity of sample surfaces with reduced adhesion of multispecies biofilm and S. mutans.

SIGNIFICANCE

Application of CCS surface treatment immediately after post-curing (CB2) can enhance the biofilm resistance of 3D printed clear aligners while maintaining high fidelity to optical translucency and constituent mechanical properties.

Electrochemical performance and structural evolution of spray pyrolyzed Mn3O4 thin films in different aqueous electrolytes: effect of anions and cations

This work presents the impact of cycling in different cationic and anionic aqueous electrolytes on the electrochemical storage performance of the Mn3O4 thin film electrode prepared using the chemical pyrolysis method. Studies on the as-deposited electrode confirmed the formation of Mn3O4 phase. Extensive electrochemical analysis was performed using Na2SO4, NaCl, Li2SO4, K2SO4, and MgSO4 electrolytes to examine the influence of cations and anions on charge storage behaviour. Considerable changes were observed in the specific capacitances owing to different ionic sizes as well as hydrated ionic radius of the electrolyte ions. Accordingly, the electrode unveiled a good performance showing a specific capacitance of around 187 F g-1 at 0.5 A g-1 in K2SO4 electrolyte. Further, the electrode properties are examined after 500 CV cycles to trace the changes in the structural and morphological properties. X-ray diffraction (XRD) and Raman spectroscopic studies illustrate a partial phase transformation of electrodes from Mn3O4 to MnO2 irrespective of the electrolytes. These results are further corroborated with X-ray photoelectron spectroscopic (XPS) analysis where there was an increment in the oxidation state of manganese. It has been observed that the surface properties were significantly changed with cycling, as manifested by the wettability studies of the electrodes. The obtained results brings out the significance of electrolyte ions on the charge storage characteristics of Mn3O4 thin film electrodes in light of their possible application in electrochemical capacitors.

Trade-off between sulfidated zero-valent iron reactivity and air stability: Regulation of iron sulfides by ammonium dihydrogen phosphate

The reactivity and stability of zero-valent iron (ZVI) and sulfidated zero-valent iron (S-ZVI) are inherently contradictory. Iron sulfides (FeSX) on the S-ZVI surface play multiple roles, including electrostatic adsorption and catalyzing reduction. We proposed to balance the reactivity and air stability of S-ZVI by regulating FeSX. Benefiting from the superior coordination and accelerate electron transport capabilities of phosphate, herein, eco-friendly ammonium dihydrogen phosphate (ADP) was employed to synthesize N, P, and S-incorporated ZVI (NPS-ZVI) and regulate the FeSX. Raman, FTIR, XPS, and density functional theory (DFT) calculations were combined to reveal that HPO42- acts as the main P species on the Fe surface. The superior reactivity of NPS-ZVI was quantified by kobs, kSA, and kM of Cr(VI), which were 210.77, 27.44, and 211.17-fold than ZVI, respectively. NPS-ZVI demonstrated excellent reusability, with no risk of secondary pollution. Critically, NPS-ZVI could effectively maintain FeSX stability under the combination of diffusion limitation and surface protection mechanisms of ADP. The superior reactivity of NPS-ZVI was attributed to the fact that ADP maintains FeSX stability and accelerates electron transport. This study provides a novel strategy in balancing the reactivity and air stability of S-ZVI and offers theoretical support for material modification.

A Spironolactone-Based Prototype of an Innovative Biomedical Patch for Wound Dressing Applications

The electrospinning process is an effective technique for creating micro- and nanofibers from synthetic and natural polymers, with significant potential for biomedical applications and drug delivery systems due to their high drug-loading capacity, large surface area, and tunable release times. Poly(L-lactic acid) (PLLA) stands out for its excellent thermo-mechanical properties, biodegradability, and bioabsorbability. Electrospun PLLA nanofibrous structures have been extensively investigated as wound dressings, sutures, drug delivery carriers, and tissue engineering scaffolds. This study aims to create and characterize electrospun PLLA membranes loaded with spironolactone (SP), mimicking active compounds of Ganoderma lucidum (GL), to develop a biodegradable patch for topical wound-healing applications. GL, a medicinal mushroom, enhances dermal wound healing with its bioactive compounds, such as polysaccharides and ganoderic acids. Focusing on GL extracts-obtained through green extraction methods-and innovative drug delivery, we created new fibers for wound-healing potential applications. To integrate complex mixtures of bioactive compounds into the fibers, we developed a prototype using a single pure substance representing the extract mixture. This painstaking work presents the results of the fabricating, wetting, moisture properties, material resilience, and full characterization of the product, providing a robust rationale for the fabrication of fibers imbued with more complex extracts.

Conductive PEDOT-Dominant Surface of Transparent Electrode Patch via Selective Phase Transfer for Efficient Flexible Photoelectronic Devices

In this study, a conductive patch for a flexible organic optoelectronic device is proposed and implemented using a poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) polymer electrode based on a transfer process to achieve its high conductivity with an efficient conductive pathway. This PEDOT-dominant surface is induced by phase inversion during the transfer process owing to the solvent affinity of the PSS phase. The PEDOT:PSS patch formed by the transfer process minimizes the power loss in a flexible optoelectronic device due to the improved charge collection and suppressed leakage current responses. In addition, the bending stability of the flexible photoelectronic device is also enhanced by maintaining performance for 1000 bending cycles. Therefore, in the fabrication of a transparent flexible conductive PEDOT:PSS patch, the transfer process of a conducting polymer constitutes an effective strategy that can improve conductivity and embellished morphology.

Measuring surface energy of solid surfaces using centrifugal adhesion balance

The standard way to evaluate the solid surface energy using probe liquids relies on contact angle measurements. The measured contact angles rely on visible means and are different from their nanoscopic thermodynamic values. This compromises the surface-energy predictions so much that the surface energy-values can be hundreds of percentages higher than expected based on comparisons with different methods as reported in several studies. We consider the Owen-Wendt approach, which breaks the surface energy to polar and dispersive components, and present a technique for measuring surface energy of solids using probe liquids. Our method avoids the need to measure contact angles; instead, it uses solid-liquid work of adhesion measurements which are performed using a centrifugal adhesion balance. In agreement with the studies mentioned above, we found that indeed, the surface energies of the measured solids are significantly lower than those based on contact angle measurements. More importantly we found that our method results in a reasonable breakdown of the surface energy to polar and dispersive components with a higher polar component for more polar solids. This is in contrast with the surface energy based on contact angle measurements for which the breakdown did not make sense, i.e., the measurements reflected higher polar components of the surface energy for less polar solids.

Hybrid Zinc Phthalocyanine/PVDF-HFP System for Reducing Biofouling in Water Desalination: DFT Theoretical and MolDock Investigations

Fouling and biofouling remain significant challenges in seawater desalination plants. One practical approach to address these issues is to develop anti-biofouling membranes. Therefore, novel hybrid zinc phthalocyanine/polyvinylidene fluoride-co-hexafluoropropylene (Zn(4-PPOx)4Pc/PVDF-HFP) membranes were prepared by electrospinning to evaluate their properties against biofouling. The hybrid nanofiber membrane was characterized by atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle measurements. The theoretical calculations of PVDF-HFP, Zn(4-PPOx)4Pc), and Zn(4-PPOx)4Pc/PVDF-HFP nanofibers were performed using a hybrid functional RB3LYP and the 6-31 G (d,p) basis set, employing Gaussian 09. DFT calculations illustrated that the calculated physical and electronic parameters ensured the feasibility of the interaction of PVDF-HFP with Zn(4-PPOx)4Pc via a halogen-hydrogen bond, resulting in a highly stable and remarkably reactive structure. Moreover, molecular electrostatic potential (MEP) maps were drawn to identify the reactive regions of the Zn(4-PPOx)4Pc and PVDF-HFP/Zn(4-PPOx)4Pc nanofibers. Molecular docking analysis revealed that Zn(4-PPOx)4Pc has highest binding affinity (-8.56 kcal/mol) with protein from S. aureus (1N67) mainly with ten amino acids (ASP405, LYS374, GLU446, ASN406, ALA441, TYR372, LYS371, TYR448, LYS374, and ALA442). These findings highlight the promising potential of Zn(4-PPOx) 4Pc/PVDF-HFP nanocomposite membranes in improving the efficiency of water desalination by reducing biofouling and providing antibacterial properties.

Reliable Determination of Contact Angle from the Liquid Fence

Traditional methods of measuring contact angles often face difficulties in precisely defining the three-phase contact points. A novel method for accurately defining three-phase contact points based on liquid fences is proposed in this article. The tested liquid is placed in a cubic liquid fence composed of a pair of narrow strips of the tested solid and a pair of transparent wide strips. The transparent wide strip serves as the measurement window, and the surface tension of the liquid on it can be almost ignored. In experimental measurements, the horizontal coordinates of the end points of the liquid profile are fixed by the liquid fence, thus determining the horizontal coordinates of the three-phase contact points, which helps to accurately survey the contact angle. Additionally, since the parameters of the liquid fence are known, the size of the contact angle can also be calculated by measuring the height of the liquid level dome inside the liquid fence. Using the electric wetting effect as an example, we experimentally extracted a series of liquid contour maps with circular tops and square columns under varying voltages. The relationship curve between contact angle and voltage variation was obtained using the above methods, and a contact angle variation tendency seemed to agree well with the theoretical value.

An integrated design strategy coupling additive manufacturing and matrix-assisted pulsed laser evaporation (MAPLE) towards the development of a new concept 3D scaffold with improved properties for tissue regeneration

Bioinspired strategies for scaffold design and optimization were improved by the introduction of Additive Manufacturing (AM), thus allowing for replicating and reproducing complex shapes and structures in a reliable manner, adopting different kinds of polymeric and nanocomposite materials properly combined according to the features of the natural host tissues. Benefiting from recent findings in AM, a Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique was employed for obtaining graphene-like material (GL) uniform coatings on 3D scaffolds for tissue repair strategies, towards the development of a new concept 3D scaffold with controlled morphological/architectural and surface features and mechanical and biological properties. The effect of the material-design combination through an integrated technological approach (i.e., MAPLE deposition of GL on 3D AM PCL scaffolds) was assessed through scanning electron microscopy, atomic force microscopy, contact angle measurements, mechanical measurements and biological analyses (cell viability assay and alkaline phosphatase activity) in conjunction with confocal laser scanning microscopy. The differentiation of hMSCs towards the osteoblast phenotype was also investigated analysing the gene expression profile. The obtained findings provided a further insight into the development of improved strategies for the functionalization or combination of GL with other materials and 3D structures in a hybrid fashion for ensuring a tighter adhesion onto the substrates, improving cell fate over time, without negatively altering the mechanical properties and behaviour of the neat constructs. In particular, the results provided interesting information, making 3D AM GL-coated scaffolds potential candidates for bone tissue engineering.

Preparation and Evaluation of Inhalable Microparticles with Improved Aerodynamic Performance and Dispersibility Using L-Leucine and Hot-Melt Extrusion

Dry-powder inhalers (DPIs) are valued for their stability but formulating them is challenging due to powder aggregation and limited flowability, which affects drug delivery and uniformity. In this study, the incorporation of L-leucine (LEU) into hot-melt extrusion (HME) was proposed to enhance dispersibility while simultaneously maintaining the high aerodynamic performance of inhalable microparticles. This study explored using LEU in HME to improve dispersibility and maintain the high aerodynamic performance of inhalable microparticles. Formulations with crystalline itraconazole (ITZ) and LEU were made via co-jet milling and HME followed by jet milling. The LEU ratio varied, comparing solubility, homogenization, and aerodynamic performance enhancements. In HME, ITZ solubility increased, and crystallinity decreased. Higher LEU ratios in HME formulations reduced the contact angle, enhancing mass median aerodynamic diameter (MMAD) size and aerodynamic performance synergistically. Achieving a maximum extra fine particle fraction of 33.68 ± 1.31% enabled stable deep lung delivery. This study shows that HME combined with LEU effectively produces inhalable particles, which is promising for improved drug dispersion and delivery.

Study on Confined Water in Flexible Graphene/GO Nanochannels

The structural evolution of flexible nanochannels within a 2D material membrane, influenced by the ingress of water molecules, plays a crucial role in the membrane's filtration and structural stability. However, the experimental observation of nanoscale water is challenging, and current studies mostly focus on rigid nanochannels. Further investigation on the nanoconfined water is urgently needed, considering the flexibility and deformation of the channel. In this work, MD simulations and theoretical analyses are conducted to investigate the water structure and thermodynamic properties when confined within both rigid and flexible graphene/graphene oxide (GO) nanochannels. In free rigid graphene nanochannels, the interlayer distance exhibits a quantized increase with the number of water molecules, along with sudden changes in entropy, potential energy, and free energy of the water molecules. Meanwhile, in flexible graphene nanochannels, the average interlayer space increases linearly with the number of water molecules. In free rigid GO nanochannels, with the increase of oxidation concentration, the quantized increase in the interlayer space gradually diminishes, accompanied by a decrease in both potential energy and free energy. This work provides insights into the configurational evolution of flexible nanochannels within water, offering guidance in fields such as desalination and mass transport of 2D material membranes.

Chemisorption-Induced Robust and Homogeneous Tungsten Disulfide Interlayer Enables Stable PEDOT-Free Organic Solar Cells with Over 19% Efficiency

Construction of a high-quality charge transport layer (CTL) with intimate contact with the substrate via tailored interface engineering is crucial to increase the overall charge transfer kinetics and stability for a bulk-heterojunction (BHJ) organic solar cell (OSC). Here, we demonstrate a surface chemistry strategy to achieve a homogeneous composite hole transport layer (C-HTL) with robust substrate contact by self-assembling two-dimensional tungsten disulfide (WS2) nanosheets on a thin molybdenum oxide (MoO3) film-evaporated indium tin oxide (ITO) substrate. It is found that over such a well-defined C-HTL, WS2 is homogeneously tethered on the ITO/MoO3 substrate stemming from the strong electronic coupling interaction between the building blocks, which enables a favorable interfacial configuration in terms of uniformity. As a result, the D18:L8-BO-based OSC with C-HTL exhibits a power conversion efficiency (PCE) of 19.23%, an 11% improvement over the WS2-based control device, and the highest efficiency among single-junction PEDOT-free binary BHJ OSCs.

Assembling 99% MOFs into Bioinspired Rigid-Flexible Coupled Membrane with Significant Permeability: The Impacts of Defects

Assembling metal-organic frameworks (MOFs) into high-performance macroscopic membranes is crucial but still challenging. MOF-containing hybrid membranes can effectively integrate the advantages of flexible guest materials and MOFs. Nevertheless, the inherent limitations in fully harnessing the distinct characteristics of MOFs persist due to the substantial guest material content necessitated in membrane fabrication. Herein, inspired by the rigid and flexible structures in biological systems, rigid MIP-202(Zr) and defective MIP-202(Zr) (D-MIP-202(Zr)) modified flexible graphene oxide (GO) sheets are synthesized in situ and then assembled into a rigid-flexible coupled MOF-based membrane. The defects in D-MIP-202(Zr) are introduced by using acetic acid as the modulation agent. The obtained GO@MIP-202(Zr) membrane possesses a hierarchical porous structure with a 99 wt% MOF proportion, which is higher than the GO@D-MIP-202(Zr) (75 wt%) membrane with a compact bulge-structured surface. The water permeability of the GO@MIP-202(Zr) membrane attains remarkedly 5762.92 L h-1 m-2 bar-1 , which is 960 and 2.6 times higher than that of the GO membrane and GO@D-MIP-202(Zr) membrane. Additionally, benefiting from the superhydrophilicity and underwater superoleophobicity, the resultant membrane not only demonstrates high rejection for oil-water emulsions but also exhibits exceptional recyclability and anti-fouling ability. These findings provide valuable insights into the assembly of MOFs into high-performance membranes.

Flowing Liquid-Based Triboelectric Nanogenerator Performance Enhancement with Functionalized Polyvinylidene Fluoride Membrane for Self-Powered Pulsating Flow Sensing Application

Pulsating flow, a common term in industrial and medical contexts, necessitates precise water flow measurement for evaluating hydrodynamic system performance. Addressing challenges in measurement technologies, particularly for pulsating flow, we propose a flowing liquid-based triboelectric nanogenerator (FL-TENG). To generate sufficient energy for a self-powered device, we employed a fluorinated functionalized technique on a polyvinylidene fluoride (PVDF) membrane to enhance the performance of FL-TENG. The results attained a maximum instantaneous power density of 50.6 µW/cm2, and the energy output proved adequate to illuminate 10 white LEDs. Regression analysis depicting the dependence of the output electrical signals on water flow revealed a strong linear relationship between the voltage and flow rate with high sensitivity. A high correlation coefficient R2 within the range from 0.951 to 0.998 indicates precise measurement accuracy for the proposed FL-TENG. Furthermore, the measured time interval between two voltage peaks precisely corresponds to the period of pulsating flow, demonstrating that the output voltage can effectively sense pulsating flow based on voltage and the time interval between two voltage peaks. This work highlights the utility of FL-TENG as a self-powered pulsating flow rate sensor.

PVA-Based Films with Strontium Titanate Nanoparticles Dedicated to Wound Dressing Application

Bioactive materials may be applied in tissue regeneration, and an example of such materials are wound dressings, which are used to accelerate skin healing, especially after trauma. Here, we proposed a novel dressing enriched by a bioactive component. The aim of our study was to prepare and characterize poly(vinyl alcohol) films modified with strontium titanate nanoparticles. The physicochemical properties of films were studied, such as surface free energy and surface roughness, as well as the mechanical properties of materials. Moreover, different biological studies were carried out, like in vitro hemo- and cyto-compatibility, biocidal activity, and anti-biofilm formation. Also, the degradation of the materials' utilization possibilities and enzymatic activity in compost were checked. The decrease of surface free energy, increase of roughness, and improvement of mechanical strength were found after the addition of nanoparticles. All developed films were cyto-compatible, and did not induce a hemolytic effect on the human erythrocytes. The PVA films containing the highest concentration of STO (20%) reduced the proliferation of Eschericha coli, Pseudomonas aeruginosa, and Staphylococcus aureus significantly. Also, all films were characterized by surface anti-biofilm activity, as they significantly lowered the bacterial biofilm abundance and its dehydrogenase activity. The films were degraded by the compost microorganism. However, PVA with the addition of 20%STO was more difficult to degrade. Based on our results, for wound dressing application, we suggest using bioactive films based on PVA + 20%STO, as they were characterized by high antibacterial properties, favorable physicochemical characteristics, and good biocompatibility with human cells.

Improved electrochemical performance of bio-derived plasticized starch/ reduced graphene oxide/ molybdenum disulfide ternary nanocomposite for flexible energy storage applications

A ternary nanocomposite of plasticized starch (PS), reduced graphene oxide (rGO), and molybdenum disulfide (MoS2) was prepared via a solution casting process, with MoS2 concentrations ranging from 0.25 to 1.00 wt%. The structural, surface morphological, optical, and electrochemical properties of the nanocomposites were studied. FTIR analysis reveals the formation of new chemical bonds between PS, rGO, and MoS2, indicating strong interactions among them. The XRD analysis showed a reduction in the crystallinity of the nanocomposite from 40 to 21% due to the incorporation of nanofiller. FESEM micrograph showed an increment of the surface roughness due to the incorporation of rGO-MoS2 layers. UV-vis spectroscopy demonstrated a reduction of optical bandgap from 4.71 to 2.90 eV, resulting from enhanced charge transfer between the layers and defect states due to the addition of nanofillers. The incorporation of MoS2 increase the specific capacitance of the PS from 2.78 to 124.98 F g-1 at a current density of 0.10 mA g-1. The EIS analysis revealed that the nanofiller significantly reduces the charge transfer resistance from 4574 to 0 Ω, facilitating the ion transportation between the layers. The PS/rGO/MoS2 nanocomposite also exhibited excellent stability, retaining about 85% of its capacitance up to 10,000 charging-discharging cycles. These biocompatible polymer-based nanocomposites with improved electrochemical performance synthesized from an easy and economical route may offer a promising direction to fabricate a nature-friendly electrode material for energy storage applications.

Corrosion-Resistant Hydrophobic Thermal Barrier Composite Coating on Metal Strip: A New Dimension to Steel Strips for Roofing Segment

This study demonstrates a cost-effective, thin, multifunctional composite coating system with outstanding thermal insulation for thermal management and heat shield applications, such as roofs, as well as outstanding resistance to corrosion. The hydrophobic multifunctional epoxy composite coating systems were designed with surface-modified fillers to impart both reduced heat conduction and high infrared reflectance in a thin coating with a 65-100 μm dry film thickness (DFT). With a judicial combination of hollow microspheres (HMS) activated and modified with silica (sHMS) and stearic acid-modified TiO2 (sMO), the developed composite coating attained the highest thermal insulation property with a temperature drop of 21-31 °C at different distances below the coated panel, which is superior to the values of temperature drop reported earlier. The high solar reflectance of the composite coating in the near-infrared (NIR) region exceeds 72% with a low thermal conductivity of 0.178 W m-1 K-1. After 720 h of exposure in a 3.5 wt % NaCl solution, the composite coating revealed a corrosion protection efficiency of 99%. The work demonstrates that high solar reflectivity and low thermal conductivity must be active simultaneously to achieve superior thermal shielding in a thin coating on a metal. A careful selection of fillers and appropriate surface modifications ensures hydrophobicity and proper distribution of the fillers in the coating for a high barrier effect to prevent environmental deterioration. With these superior performance parameters, the developed composite coatings make an essential contribution to energy sustainability and the protection against environmental degradation.

Overcoming Water Diffusion Limitations in Hydrogels via Microtubular Graphene Networks for Soft Actuators

Hydrogel-based soft actuators can operate in sensitive environments, bridging the gap of rigid machines interacting with soft matter. However, while stimuli-responsive hydrogels can undergo extreme reversible volume changes of up to ≈90%, water transport in hydrogel actuators is in general limited by their poroelastic behavior. For poly(N-isopropylacrylamide) (PNIPAM) the actuation performance is even further compromised by the formation of a dense skin layer. Here it is shown, that incorporating a bioinspired microtube graphene network into a PNIPAM matrix with a total porosity of only 5.4% dramatically enhances actuation dynamics by up to ≈400% and actuation stress by ≈4000% without sacrificing the mechanical stability, overcoming the water transport limitations. The graphene network provides both untethered light-controlled and electrically powered actuation. It is anticipated that the concept provides a versatile platform for enhancing the functionality of soft matter by combining responsive and 2D materials, paving the way toward designing soft intelligent matter.

Graphene-Based Physically Unclonable Functions with Dual Source of Randomness

There is growing interest in systems with randomized responses for generating physically unclonable functions (PUFs) in anticounterfeiting and authentication applications. Atomic-level control over its thickness and unique Raman spectrum make graphene an attractive material for PUF applications. Herein, we report graphene PUFs that emerge from two independent stochastic processes. Randomized variations in the shape and number of graphene adlayers were achieved by exploiting and improving the mechanistic understanding of the chemical vapor deposition of graphene. The randomized positioning of the graphene domains was then facilitated by dewetting the polymer film, followed by oxygen plasma etching. This approach yielded surfaces with randomly positioned and shaped graphene islands with varied numbers of layers and, therefore, Raman spectra. Raman mapping of surfaces resulted in multicolor images with a high encoding capacity. Advanced feature-matching algorithms were employed for the authentication of multicolor images. The use of two independent stochastic processes on a two-dimensional nanomaterial platform enables the creation of unique and complex surfaces that excessively challenge clonability.

Experimental determination of surface energy for high-energy surface: A review

The experimental determination of surface free energy is of great importance for engineering applications. However, there is no universal, reliable, and convenient measurement means to achieve experimental determination of solid surface energy for high-energy surface. In this work, the existing techniques for experimental determination of surface energy of solids, including indirect (4 kinds) and direct methods (3 kinds), were critically reviewed. In the indirect methods: the explicit interfacial bonding characteristics are required for the multiphase equilibrium technique and for the determination method from crystal equilibrium shape; the critical surface energy technique does not satisfy Zisman's hypothesis that the solid-liquid interface tension is zero (or close to zero), and the parameters fitted by empirical equations cannot have definite physical meaning; the derivation based on the surface tension in the liquid state can only obtain the surface energy of the solid phase near the melting point, and is limited to the prediction of the surface energy of elemental metal. Among the direct determination methods, except for the zero-creep method, are based on generalized determination technologies. All determined results are strongly influenced by the accuracy of the particle (grain) size, scale effect, the atmosphere, etc. This leads to the fact that the errors are still huge regardless of the determination method used, and it is difficult to achieve uniformity of the data. All methods rely to some extent on specific assumptions or theoretical models.

Anion Intercalation into Graphite Drives Surface Wetting

The unique layered structure of graphite with its tunable interlayer distance establishes almost ideal conditions for the accommodation of ions into its structure. The smooth and chemically inert nature of the graphite surface also means that it is an ideal substrate for electrowetting. Here, we combine these two unique properties of this material by demonstrating the significant effect of anion intercalation on the electrowetting response of graphitic surfaces in contact with concentrated aqueous and organic electrolytes as well as ionic liquids. The structural changes during intercalation/deintercalation were probed using in situ Raman spectroscopy, and the results were used to provide insights into the influence of intercalation staging on the rate and reversibility of electrowetting. We show, by tuning the size of the intercalant and the stage of intercalation, that a fully reversible electrowetting response can be attained. The approach is extended to the development of biphasic (oil/water) systems that exhibit a fully reproducible electrowetting response with a near-zero voltage threshold and unprecedented contact angle variations of more than 120° within a potential window of less than 2 V.

Selective-Area Growth Mechanism of GaN Microrods on a Plateau Patterned Substrate

This study provides experimental evidence regarding the mechanism of gallium nitride (GaN) selective-area growth (SAG) on a polished plateau-patterned sapphire substrate (PP-PSS), on which aluminum nitride (AlN) buffer layers are deposited under the same deposition conditions. The SAG of GaN was only observed on the plateau region of the PP-PSS, irrespective of the number of growth cycles. Indirect samples deposited on the bare c-plane substrate were prepared to determine the difference between the AlN buffer layers in the plateau region and silicon oxide (SiO2). The AlN buffer layer in the plateau region exhibited a higher surface energy, and its crystal orientation is indicated by AlN [001]. In contrast, regions other than the plateau region did not exhibit crystallinity and presented lower surface energies. The direct analysis results of PP-PSS using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) are similar to the results of the indirect samples. Therefore, under the same conditions, the GaN SAG of the deposited layer is related to crystallinity, crystal orientation, and surface energy.

Determination of Hydrophobic Dispersive Surface Free Energy of Activated Carbon Fibers Measured by Inverse Gas Chromatographic Technique

Activated carbon fibers (ACFs) as one of the most important porous carbon materials are widely used in many applications that involve rapid adsorption and low-pressure loss, including air purification, water treatment, and electrochemical applications. For designing such fibers for the adsorption bed in gas and aqueous phases, in-depth comprehension of the surface components is crucial. However, achieving reliable values remains a major challenge due to the high adsorption affinity of ACFs. To overcome this problem, we propose a novel approach to determine London dispersive components (γSL) of the surface free energy of ACFs by inverse gas chromatography (IGC) technique at an infinite dilution. Our data reveal the γSL values at 298 K for bare carbon fibers (CFs) and the ACFs to be 97 and 260-285 mJ·m^-2, respectively, which lie in the regime of secondary bonding of physical adsorption. Our analysis indicates that these are impacted by micropores and defects on the carbon surfaces. Comparing the γSL obtained by the traditional Gray's method, our method is concluded as the most accurate and reliable value for the hydrophobic dispersive surface component of porous carbonaceous materials. As such, it could serve as a valuable tool in designing interface engineering in adsorption-related applications.

Precise quantification of nanoparticle surface free energy via colloidal probe atomic force microscopy

Interfacial interactions of nanoparticles (NPs) in colloids are greatly influenced by the NP surface free energy (SFE). Due to the intrinsic physical and chemical heterogeneity of the NP surface, measuring SFE is nontrivial. The use of direct force measurement methods, such as colloidal probe atomic force microscopy (CP-AFM), have been proven to be effective for the determination of SFE on relatively smooth surfaces, but fail to provide reliable measurements for rough surfaces generated by NPs. Here, we developed a reliable approach to determine the SFE of NPs by adopting Persson's contact theory to include the effect of surface roughness on the measurements in CP-AFM experiments. We obtain the SFE for a range of materials varying in surface roughness and surface chemistry. The reliability of the proposed method is verified by the SFE determination of polystyrene. Subsequently, the SFE of bare and functionalized silica, graphene oxide, and reduced graphene oxide were quantified and validity of the results was demonstrated. The presented method unlocks the potential of CP-AFM as a robust and reliable method of the SFE determination of nanoparticles with a heterogeneous surface, which is challenging to obtain with conventionally implemented experimental techniques.

Architecturally simple organic photodiodes with highly competitive figures of merit via a facile self-assembly strategy

Photodetectors (PDs) based on organic materials exhibit potential advantages such as low-temperature processing, and superior mechanical properties and form factors. They have seen rapid strides toward achieving performance metrics comparable to inorganic counterparts. Here, a simplified device architecture is employed to realize stable and high-performance organic PDs (OPDs) while further easing the device fabrication process. In contrast to the sequential deposition of the hole blocking layer (HBL) and active layer (conventional 'two-step' processing), the proposed strategy forms a self-assembled HBL and active layer in a 'single-step' process. A high-performance UV-Vis-NIR OPD based on the PM6:BTP-eC9 system is demonstrated using this cost-effective processing strategy. The green solvent processed proof-of-concept device exhibits remarkable responsivity of ∼0.5 A W^-1, lower noise current than conventional two-step OPD, ultrafast rise/fall times of 1.4/1.6 μs (comparable to commercial silicon diode), and a broad linear dynamic range of 140 dB. Importantly, highly stable (light and heat) devices compared to those processed by the conventional method are realized. The broad application potential of this elegant strategy is proven by demonstrating the concept in three representative systems with broadband sensing competence.

Surface characterization of alkane viral anchoring films prepared by titanate-assisted organosilanization

Studies of virus adsorption on surfaces with optimized properties have attracted a lot of interest, mainly due to the influence of the surface in the retention, orientation and stability of the viral capsids. Besides, viruses in whole or in parts can be used as cages or vectors in different areas, such as biomedicine and materials science. A key requirement for virus nanocage application is their physical properties, i.e. their mechanical response and the distribution of surface charge, which determine virus-substrate interactions and stability. In the present work we show two examples of viruses exhibiting strong surface interactions on homogeneous hydrophobic surfaces. The surfaces were prepared by titanate assisted organosilanization, a sol-gel spin coating process, followed by a mild annealing step. We show by surface and interface spectroscopies that the process allows trapping triethoxy-octylsilane (OCTS) molecules, exhibiting a hydrophobic alkane rich surface finishing. Furthermore, the surfaces remain flat and behave as more efficient sorptive surfaces for virus particles than mica or graphite (HOPG). Also, we determine by atomic force microscopy (AFM) the mechanical properties of two types of viruses (human adenovirus and reovirus) and compare the results obtained on the OCTS functionalized surfaces with those obtained on mica and HOPG. Finally, the TIPT+OCTS surfaces were validated as platforms for the morphological and mechanical characterization of virus particles by using adenovirus as initial model and using HOPG and mica as standard control surfaces. Then, the same characteristics were determined on reovirus using TIPT+OCTS and HOPG, as an original contribution to the catalogue of physical properties of viral particles.

The Surface Energy of Hydrogenated and Fluorinated Graphene

The surface energy of graphene and its chemical derivatives governs fundamental interfacial interactions like molecular assembly, wetting, and doping. However, quantifying the surface energy of supported two-dimensional (2D) materials, such as graphene, is difficult because (1) they are so thin that electrostatic interactions emanating from the underlying substrate are not completely screened, (2) the contribution from the monolayer is sensitive to its exact chemical state, and (3) the adsorption of airborne contaminants, as well as contaminants introduced during transfer processing, screens the electrostatic interactions from the monolayer and underlying substrate, changing the determined surface energy. Here, we determine the polar and dispersive surface energy of bare, fluorinated, and hydrogenated graphene through contact angle measurements with water and diiodomethane. We accounted for many contributing factors, including substrate surface energies and combating adsorption of airborne contaminants. Hydrogenating graphene raises its polar surface energy with little effect on its dispersive surface energy. Fluorinating graphene lowers its dispersive surface energy with a substrate-dependent effect on its polar surface energy. These results unravel how changing the chemical structure of graphene modifies its surface energy, with applications for hybrid nanomaterials, bioadhesion, biosensing, and thin-film assembly.

Interfacial Liquid Water on Graphite, Graphene, and 2D Materials

The optical, electronic, and mechanical properties of graphite, few-layer, and two-dimensional (2D) materials have prompted a considerable number of applications. Biosensing, energy storage, and water desalination illustrate applications that require a molecular-scale understanding of the interfacial water structure on 2D materials. This review introduces the most recent experimental and theoretical advances on the structure of interfacial liquid water on graphite-like and 2D materials surfaces. On pristine conditions, atomic-scale resolution experiments revealed the existence of 1-3 hydration layers. Those layers were separated by ∼0.3 nm. The experimental data were supported by molecular dynamics simulations. However, under standard working conditions, atomic-scale resolution experiments revealed the presence of 2-3 hydrocarbon layers. Those layers were separated by ∼0.5 nm. Linear alkanes were the dominant molecular specie within the hydrocarbon layers. Paradoxically, the interface of an aged 2D material surface immersed in water does not have water molecules on its vicinity. Free-energy considerations favored the replacement of water by alkanes.

Gold Nanoparticles-MWCNT Based Aptasensor for Early Diagnosis of Prostate Cancer

Prostate cancer is one of the most frequently diagnosed male malignancies and can be detected by prostate-specific antigen (PSA) as a biomarker. To detect PSA, several studies have proposed using antibodies, which are not economical and require a long reaction time. In this study, we propose to use self-assembled thiolated single-strand DNA on electrodes functionalized by multi-walled carbon nanotubes (MWCNT) modified with gold nanoparticles (AuNPs) to realize a low-cost label-free electrochemical biosensor. In this regard, the PSA aptamer was immobilized via electrostatic adsorption on the surface of a screen-printed MWCNT/AuNPs electrode. The immobilization process was enhanced due to the presence of Au nanoparticles on the surface of the electrode. Surface characterization of the electrode at different stages of modification was performed by electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) and contact angle for surface tension properties. The results showed an increase in surface roughness due to the absorbance of the aptamer on the electrode surfaces. The developed sensor has an extended linear range of 1-100 ng/mL, and a very low limit of detection down to 1 pg/mL. In addition, the reaction has a binding time of only five minutes on the developed electrodes. Investigations of the biosensor selectivity against several substances revealed an efficient selectivity for PSA detection. With this approach, low-cost biosensors with high sensitivity can be realized which have a wide linearity range and a low limit of detection, which are necessary for the early detection of prostate cancer.

Machine Learning-Based Rapid Detection of Volatile Organic Compounds in a Graphene Electronic Nose

Rapid detection of volatile organic compounds (VOCs) is growing in importance in many sectors. Noninvasive medical diagnoses may be based upon particular combinations of VOCs in human breath; detecting VOCs emitted from environmental hazards such as fungal growth could prevent illness; and waste could be reduced through monitoring of gases produced during food storage. Electronic noses have been applied to such problems, however, a common limitation is in improving selectivity. Graphene is an adaptable material that can be functionalized with many chemical receptors. Here, we use this versatility to demonstrate selective and rapid detection of multiple VOCs at varying concentrations with graphene-based variable capacitor (varactor) arrays. Each array contains 108 sensors functionalized with 36 chemical receptors for cross-selectivity. Multiplexer data acquisition from 108 sensors is accomplished in tens of seconds. While this rapid measurement reduces the signal magnitude, classification using supervised machine learning (Bootstrap Aggregated Random Forest) shows excellent results of 98% accuracy between 5 analytes (ethanol, hexanal, methyl ethyl ketone, toluene, and octane) at 4 concentrations each. With the addition of 1-octene, an analyte highly similar in structure to octane, an accuracy of 89% is achieved. These results demonstrate the important role of the choice of analysis method, particularly in the presence of noisy data. This is an important step toward fully utilizing graphene-based sensor arrays for rapid gas sensing applications from environmental monitoring to disease detection in human breath.

Which Surface Is More Scaling Resistant? A Closer Look at Nucleation Theories for Heterogeneous Gypsum Nucleation in Aqueous Solutions

Developing engineered surfaces with scaling resistance is an effective means to inhibit surface-mediated mineral scaling in various industries including desalination. However, contrasting results have been reported on the relationship between scaling potential and surface hydrophilicity. In this study, we combine a theoretical analysis with experimental investigation to clarify the effect of surface wetting property on heterogeneous gypsum (CaSO₄·2H₂O) formation on surfaces immersed in aqueous solutions. Theoretical prediction derived from classical nucleation theory (CNT) indicates that an increase of surface hydrophobicity reduces scaling potential, which contrasts our experimental results that more hydrophilic surfaces are less prone to gypsum scaling. We further consider the possibility of nonclassical pathway of gypsum nucleation, which proceeds by the aggregation of precursor clusters of CaSO₄. Accordingly, we investigate the affinity of CaSO₄ to substrate surfaces of varied wetting properties via calculating the total free energy of interaction, with the results perfectly predicting experimental observations of surface scaling propensity. This indicates that the interactions between precursor clusters of CaSO₄ and substrate surfaces might play an important role in regulating heterogeneous gypsum formation. Our findings provide evidence that CNT might not be applicable to describing gypsum scaling in aqueous solutions. The fundamental insights we reveal on gypsum scaling mechanisms have the potential to guide rational design of scaling-resistant engineered surfaces.

The composition and structure of the ubiquitous hydrocarbon contamination on van der Waals materials

The behavior of single layer van der Waals (vdW) materials is profoundly influenced by the immediate atomic environment at their surface, a prime example being the myriad of emergent properties in artificial heterostructures. Equally significant are adsorbates deposited onto their surface from ambient. While vdW interfaces are well understood, our knowledge regarding atmospheric contamination is severely limited. Here we show that the common ambient contamination on the surface of: graphene, graphite, hBN and MoS₂ is composed of a self-organized molecular layer, which forms during a few days of ambient exposure. Using low-temperature STM measurements we image the atomic structure of this adlayer and in combination with infrared spectroscopy identify the contaminant molecules as normal alkanes with lengths of 20-26 carbon atoms. Through its ability to self-organize, the alkane layer displaces the manifold other airborne contaminant species, capping the surface of vdW materials and possibly dominating their interaction with the environment.

Here, the authors attribute the ambient surface contamination of van der Waals materials to a self-organized molecular layer of normal alkanes with lengths of 20-26 carbon atoms. The alkane adlayer displaces the manifold other airborne contaminant species, capping the surface of graphene, graphite, hBN and MoS₂.

Non-Supported and PET-Supported Chitosan Membranes for Pervaporation: Production, Characterization, and Performance

The objective of this study was to develop non-supported and PET-supported chitosan membranes that were cross-linked with glutaraldehyde, then evaluate their physical-chemical, morphological, and mechanical properties, and evaluate their performance in the separation of ethanol/water and limonene/linalool synthetic mixtures by hydrophilic and target-organophilic pervaporation, respectively. The presence of a PET layer did not affect most of the physical-chemical parameters of the membranes, but the mechanical properties were enhanced, especially the Young modulus (76 MPa to 398 MPa), tensile strength (16 MPa to 27 MPa), and elongation at break (7% to 26%), rendering the supported membrane more resistant. Regarding the pervaporation tests, no permeate was obtained in target-organophilic pervaporation tests, regardless of membrane type. The support layer influenced the hydrophilic pervaporation parameters of the supported membrane, especially in reducing transmembrane flux (0.397 kg∙m-2∙h-1 to 0.121 kg∙m-2∙h-1) and increasing membrane selectivity (611 to 1974). However, the pervaporation separation index has not differed between membranes (228 for the non-supported and 218 for the PET-supported membrane), indicating that, overall, both membranes had a similar performance. Thus, the applicability of each membrane is linked to specific applications that require a more resistant membrane, greater transmembrane fluxes, and higher selectivity.

Controlled synthesis of solid-shelled non-spherical and faceted microbubbles

The ability to control the shape of hollow particles (e.g., capsules or bubbles) holds great promise for enhancing the encapsulation efficiency and mechanical/optical properties. However, conventional preparation methods suffer from a low yield, difficulty in controlling the shape, and a tedious production process, limiting their widespread application. Here, we present a method for fabricating polyhedral graphene oxide (GO)-shelled microbubbles with sharp edges and vertices, which is based on the microfluidic generation of spherical compound bubbles followed by shell deformation. Sphere-to-polytope deformation is a result of the shell instability due to gradual outward gas transport, which is dictated by Laplace pressure across the shell. The shape-variant behaviours of the bubbles can also be attributed to the compositional heterogeneity of the shells. In particular, the high degree of control of microfluidic systems enables the formation of non-spherical bubbles with various shapes; the structural motifs of the bubbles are easily controlled by varying the size and thickness of the mid-shell in compound bubbles, ranging from tetrahedra to octahedra. The strategy presented in this study provides a new route for fabricating 3D structured solid bubbles, which is particularly advantageous for the development of high-performance mechanical or thermal material applications.

Revisiting the Surface Energy Parameters of Standard Test Liquids with a Corrected Contact Angle Method over Rough Surfaces

Interfacial free energy is a quantitative basis for explaining and predicting interfacial behavior that is ubiquitous in nature. The contact angle (CA) method can determine the surface free energy (γ) as well as Lifshitz-van der Waals (γ^LW) and Lewis acid/base (γ⁺/γ^-) components of a solid material from its CAs with a set of known test liquids according to the extended Young-Dupré equation. However, the reliability of the "known" parameters of the test liquids is questioned due to the long-neglected surface roughness effect during calibration of the liquids. This study proposed a simple and practicable two-step approach to correct the energy parameters of several test liquids by incorporating Wenzel's surface roughness relationship into CA measurement. Step 1: water and two apolar liquids (diiodomethane and α-bromonaphthalene) were used as benchmarks to calibrate the surface roughness and energy parameters of two reference solids [apolar poly(tetrafluoroethylene) and monopolar poly(methyl methacrylate)], and step 2: the reference solids were used to calibrate any other test liquids by solving the energy parameters from their CAs in the extended Young-Dupré-Wenzel model. Monte Carlo simulation was used to evaluate error transmission and robustness of the model solutions. The obtained energy parameters (γ^LW/γ⁺/γ^-) of four test liquids (dimethyl sulfoxide, formamide, ethylene glycol, and glycerol) are 28.01/13.68/4.67, 34.95/3.53/37.62, 26.26/7.51/15.74, and 32.99/9.24/26.02 mJ/m², respectively, and different from the literature values. The liquids were applied to characterize an example solid surface with true γ^LW/γ⁺/γ^- values of 28.00/1.00/8.00 mJ/m² and a roughness index (r) of 1.60. Without correction of the liquid parameters, the calculated surface energy, hydration energy, and hydrophobic attraction energy of the solid sample can deviate by 50, 13, and 27%, respectively. This proves the necessity of correcting parameters of the test liquids before they can be used in CA and interfacial energy studies in the presence of surface roughness.

Photocatalytic effect-assisted antimicrobial activities of acrylic resin incorporating zinc oxide nanoflakes

To overcome the deficiency of the antimicrobial effect of polymer, zinc oxide nanoparticles have been widely utilized as advanced nanofillers due to their antimicrobial and photocatalytic activity. However, the underlying antimicrobial mechanism has not been fully understood apart from topological and physical characteristics. In this study, we prepared zinc oxide nanoparticles-based acrylic resin to explore its antimicrobial mechanism under controlled mechanophysical conditions by using silane-treated zinc oxide nanoflakes (S-ZnNFs). S-ZnNFs incorporated acrylic resin (poly(methyl methacrylate), PMMA) composites up to 2 wt% were selected based on comparable mechanophysical properties (e.g., roughness, wettability, strength and hardness), possibly affecting antimicrobial properties beyond the zinc oxide nanoparticle effect, to bare PMMA. Antimicrobial adhesion results were still observed in 2 wt% S-ZnNFs incorporated PMMA using Candida albicans (C. albicans), one of the fungal infection species. In order to confirm the antimicrobial effects by photocatalysis, we pre-exposed the UV light on 2 wt% S-ZnNF composites before cell seeding, revealing synergetic antimicrobial effect via additional reactive oxygen species (ROS) generation to C. albicans over zinc oxide nanoparticle-induced one. RNA-seq analysis revealed distinguished cellular responses between zinc oxide nanoparticles and UV-mediated photocatalytic effect, but both linked to generation of intracellular ROS. Thus, the above data suggest that induction of high intracellular ROS of C. albicans was the main antimicrobial mechanism under controlled mechanophysical parameters and synergetic ROS accumulation can be induced by photocatalysis, recapitulating a promising use of a S-ZnNFs or possibly zinc oxide nanoparticles as intracellular-ROS-generating antimicrobial nanofillers in acrylic composite for biomedical applications.

An Anode-Free Potassium-Metal Battery Enabled by a Directly Grown Graphene-Modulated Aluminum Current Collector

Potassium (K)-metal batteries have emerged as a promising energy-storage device owing to abundant K resources. An anode-free architecture that bypasses the need for anode host materials can deliver an elevated energy density. However, the poor efficiency of K plating/stripping on potassiophobic anode current collectors results in rapid K inventory loss and a short cycle life. Herein, commercial Al foils are decorated with an ultrathin graphene-modified layer (Al@G) through roll-to-roll plasma-enhanced chemical vapor deposition. By harnessing strong adhesion (10.52 N m^-1 ) and a high surface energy (66.6 mJ m^-2 ), the designed Al@G structure ensures a highly smooth and ordered K plating/stripping process. Consequently, during K-metal plating/stripping, Al@G can operate at a current density of up to 4.0 mA cm^-2 and cyclic capacity of up to 4.0 mAh cm^-2 , with an ultralong lifespan of up to 1000 h at 0.5 mA cm^-2 and stable cycling of up to 750 h under periodic current fluctuations of 0.1-2.0 mA cm^-2 . In addition, a novel anode-free K-metal full-cell prototype enabled by Al@G anode current collectors is constructed, demonstrating ameliorative cyclic stability.

Antibacterial and hemostatic capacities of cellulose nanocrystalline-reinforced poly(vinyl alcohol) electrospun mats doped with Tiger 17 and pexiganan peptides for prospective wound healing applications

Infection is a major issue in chronic wound care. Different dressings have been developed to prevent microbial propagation, but an effective, all-in-one (cytocompatible, antimicrobial and promoter of healing) solution is still to be uncovered. In this research, polyvinyl alcohol (PVA) nanofibrous mats reinforced with cellulose nanocrystal (CNC), at 10 and 20% v/v ratios, were produced by electrospinning, crosslinked with glutaraldehyde vapor and doped with specialized peptides. Crosslinking increased the mats' fiber diameters but maintained their bead-free morphology. Miscibility between polymers was confirmed by Fourier-transform infrared spectroscopy and thermal evaluations. Despite the incorporation of CNC having reduced the mats' mechanical performance, it improved the mats' surface energy and its structural stability over time. Pexiganan with an extra cysteine group was functionalized onto the mats via hydroxyl- polyethylene glycol 2-maleimide, while Tiger 17 was physisorbed to preserve its cyclic conformation. Antimicrobial assessments demonstrated the peptide-doped mat's effectiveness against Staphylococcus aureus and Pseudomonas aeruginosa; pexiganan contributed mostly for such outcome. Tiger 17 showed excellent capacity in accelerating clotting. Cytocompatibility evaluations attested to these mats' safety. C90/10 PVA/CNC mats were deemed the most effective from the tested group and, thus, a potentially effective option for chronic wound treatments.

Surface Properties of CVD-Grown Graphene Transferred by Wet and Dry Transfer Processes

Graphene, an atomically thin material, has unique electrical, mechanical, and optical properties that can enhance the performance of thin film-based flexible and transparent devices, including gas sensors. Graphene synthesized on a metallic catalyst must first be transferred onto a target substrate using wet or dry transfer processes; however, the graphene surface is susceptible to chemical modification and mechanical damage during the transfer. Defects on the graphene surface deteriorate its excellent intrinsic properties, thus reducing device performance. In this study, the surface properties of transferred graphene were investigated according to the transfer method (wet vs. dry) and characterized using atomic force microscopy, Raman spectroscopy, and contact angle measurements. After the wet transfer process, the surface properties of graphene exhibited tendencies similar to the poly(methyl methacrylate) residue remaining after solvent etching. The dry-transferred graphene revealed a surface closer to that of pristine graphene, regardless of substrates. These results provide insight into the utilization of wet and dry transfer processes for various graphene applications.

Fundamentals and utilization of solid/ liquid phase boundary interactions on functional surfaces

The affinity of macroscopic solid surfaces or dispersed nano- and bioparticles towards liquids plays a key role in many areas from fluid transport to interactions of the cells with phase boundaries. Forces between solid interfaces in water become especially important when the surface texture or particles are in the colloidal size range. Although, solid-liquid interactions are still prioritized subjects of materials science and therefore are extensively studied, the related literature still lacks in conclusive approaches, which involve as much information on fundamental aspects as on recent experimental findings related to influencing the wetting and other wetting-related properties and applications of different surfaces. The aim of this review is to fill this gap by shedding light on the mechanism-of-action and design principles of different, state-of-the-art functional macroscopic surfaces, ranging from self-cleaning, photoreactive or antimicrobial coatings to emulsion separation membranes, as these surfaces are gaining distinguished attention during the ongoing global environmental and epidemic crises. As there are increasing numbers of examples for stimulus-responsive surfaces and their interactions with liquids in the literature, as well, this overview also covers different external stimulus-responsive systems, regarding their mechanistic principles and application possibilities.

A Simple and Precise Estimation of Water Sliding Angle by Monitoring Image Brightness: A Case Study of the Fluid Repellency of Commercial Face Masks

Fluid repellency of a hydrophobic surface has been typically demonstrated in terms of water sliding angle. A drop shape analysis method with a written computer algorithm monitoring the image brightness was proposed to precisely estimate the sliding angle. A hydrophobic surface coated with silanized silicon dioxide or polytetrafluoroethylene was selected as a known sample for the method validation. Average pixel brightness in an 8-bit grayscale unit rapidly increased after a water drop rolled off the surface, thus removing its black pixels. The resulting sliding angle was then determined as the tilt angle of the sample stage related to the sliding time at the brightness leap. The optimized angular speed of the rotor at 0.1 degrees per frame was chosen to avoid an overestimation of the sliding angle due to the deceleration. The proposed method yielded accurate sliding angles with an error of less than 0.2 degrees. It was then applied to study the fluid resistance of commercial face masks including disposable surgical masks and reusable fabric masks. It was found that the outermost layer of the single-use surgical masks can moderately repel a water drop with a sliding angle of 49.4 degrees. Meanwhile, the pre-coated fabric masks retained high protection efficiency at a sliding angle of less than 45 degrees after about 20 wash cycles. In addition, a raw muslin fabric coated with a commercial water-repellent spray could be a promising and affordable alternative to the surgical mask during the pandemic with high water repellency even after a few washes. The results suggested that, besides the hydrophobicity indicated by the typical contact angle, the precise sliding angle estimated by the proposed alternative method could additionally provide crucial information that might lead to a detailed discussion of the fluid repellency of rough materials.