Simple Surface Research Articles

Enhancing the ultrasonic plastic welding strength of Al/CFRTP joint via coated metal surface and structured composite surface

Ultrasonic plastic welding (UPW) is a promising technology for joining metal to carbon fiber reinforced thermoplastic composite (CFRTP) but shows poor joint strength in the existing studies. This work conducts UPW of AA6061 aluminum alloy to carbon fiber reinforced PA66 (CF/PA66) by employing a polymer coating as an interlayer. Simple metal surface grinding and silane coupling agent (SCA) treatment are used to strengthen the bonding of the metal/coating interface. Structured CF/PA66 surface fabricated by ultrasonic embossing acts as energy directors to improve the bonding strength of the coating/plastic interface. The results show that relatively high tensile-shear strength (about 31.0 MPa) can be obtained. Micro-mechanical interlocking and chemical bonding (Al-O-C and Al-O-Si bonds) are considered as the bonding mechanism of the metal/coating interface.

Polyvinylchloride surface modified with polymer brushes for reduced protein, cell and bacteria attachment

AbstractThe objective of this study was to coat negatively charged polymer brushes by a covalent bond onto the surface of polyvinylchloride using a simple conventional surface free radical polymerisation technique. The coated surfaces were assessed with contact angle, protein adsorption, cell adhesion, and bacterial adhesion. Bovine serum albumin and bovine fibrinogen were used for protein adsorption evaluation. Mouse fibroblast (NIH‐3T3) cells and Pseudomonas aeruginosa were used to assess surface adhesion. Results show that the surface modified with all the attached polymers exhibited significantly reduced contact angle, protein adsorption, and cell as well as bacterial adhesion among which the negatively charged polymers showed extremely low values in all the tests. The negatively charged polymer shows its contact angle at 5° as compared to 70° for original polyvinylchloride. Its bovine serum albumin, bovine fibrinogen, 3T3 adhesion, and P. aeruginosa adhesion were 93%, 84%, 92%, and 92% lower than the original PVC, respectively. Furthermore, the polyvinylchloride surface coated with negatively charged polymer brushes exhibited a hydrogel‐like property. The results indicate that coating a polyvinylchloride surface with acrylic acids using a simple surface‐initiated free radical polymerisation and then converting those to negatively charged salts can be an effective and efficient route for fouling‐resistant applications.

Large-Eddy Simulations of the Tropical Cyclone Boundary Layer at Landfall in an Idealized Urban Environment

Abstract Populated urban areas along many coastal regions are vulnerable to landfalling tropical cyclones (TCs). To the detriment of surface parameterizations in mesoscale models, the complexities of turbulence at high TC wind speeds in urban canopies are presently poorly understood. Thus, this study explores the impacts of urban morphology on TC-strength winds and boundary layer turbulence in landfalling TCs. To better quantify how urban structures interact with TC winds, large-eddy simulations (LESs) are conducted with the Cloud Model 1 (CM1). This implementation of CM1 includes immersed boundary conditions (IBCs) to represent buildings and eddy recycling to maintain realistic turbulent flow perturbations. Within the IBCs, an idealized coastal city with varying scales is introduced. TC winds impinge perpendicularly to the urbanized coastline. Numerical experiments show that buildings generate distinct, intricate flow patterns that vary significantly as the city structure is varied. Urban IBCs produce much stronger turbulent kinetic energy than is produced by conventional surface parameterizations. Strong effective eddy viscosity due to resolved eddy mixing is displayed in the wake of buildings within the urban canopy, while deep and enhanced effective eddy viscosity is present downstream. Such effects are not seen in a comparison LES using a simple surface parameterization with high roughness values. Wind tunneling effects in streamwise canyons enhance pedestrian-level winds well beyond what is possible without buildings. In the arena of regional mesoscale modeling, this type of LES framework with IBCs can be used to improve parameters in surface and boundary layer schemes to more accurately represent the drag coefficient and the eddy viscosity in landfalling TC boundary layers. Significance Statement This is among the first large-eddy simulation model studies to examine the impacts of tropical cyclone–like winds around explicitly resolved buildings. This work is a step forward in bridging the gap between engineering studies that use computational fluid dynamics models or laboratory experiments for flow through cities and mesoscale model simulations of landfalling tropical cyclones that use surface parameterizations specialized for urban land use.

Distinguishing surface-links described by 4-charts with two crossings and eight black vertices

Charts are oriented labeled graphs in a disk. Any simple surface braid (2-dimensional braid) can be described by using a chart. Also, a chart represents an oriented closed surface (called a surface-link) embedded in 4-space. In this paper, we investigate surface-links by using charts. In [T. Nagase and A. Shima, The structure of a minimal [Formula: see text]-chart with two crossings I: Complementary domains of [Formula: see text], J. Knot Theory Ramifactions 27(14) (2018) 1850078; T. Nagase and A. Shima, The structure of a minimal [Formula: see text]-chart with two crossings II: Neighbourhoods of [Formula: see text], Revista de la Real Academia de Ciencias Exactas, Fiskcas y Natrales. Serie A. Math. 113 (2019) 1693–1738, arXiv:1709.08827v2 ] we gave an enumeration of the charts with two crossings. In particular, there are two classes for 4-charts with two crossings and eight black vertices. The first class represents surface-links each of which is connected. The second class represents surface-links each of which is exactly two connected components. In this paper, by using quandle colorings, we shall show that the charts in the second class represent different surface-links.

Building hybrid structure of monolayered S-depleted Mo–S nanocrystals and 3D graphene towards promising aqueous supercapacitor applications

Two-dimensional (2D) 1H molybdenum disulfide (1H-MoS2) is hard to be directly used in energy storage devices due to its inert basal plane and unfavorable 2D stacking. This work demonstrated how the basal plane of 1H MoS2 nanocrystals (NCs) can be activated to offer doubled specific capacitance by simple surface S depletions. Building on the expanded graphene with three-dimensional (3D) structures, as-prepared NCs were chemically grafted on the graphene surface to deliver stable energy storage and high capacitance, which overcame above challenges of 1H-MoS2. Aside from the mostly focused metastable phase, this work confirmed that the stable 1H Mo–S material is also promising in energy storage applications.

Using particle-loaded inks to selectively change the material properties in binder-jetted WC–Co parts

Functionally graded hardmetals offer a superior combination of fracture toughness and wear resistance and alleviate the compromise that conventional hardmetals must face between these two material properties. In tooling applications, they exhibit superior cutting performance compared to the conventionally employed hardmetals. Traditionally, graded tools are enabled by a surface treatment with nitrogen or carbon. This enables a tungsten carbide–cobalt (WC–Co) tool with a surface layer containing less cobalt (Co) than the core of the part. With this Co gradation, the wear properties can be improved due to the harder surface. If different loads act at different points in a tool and the geometric complexity of a tool increases, the requirements for a targeted positioning of the Co gradients become higher. A simple surface treatment does not allow a flexible distribution of the desired gradients. Binder jetting provides a solution to produce location-independent graded structures. In this work, the process was evaluated for the generation of Co gradients in WC–Co structures. Inks loaded with graphite particle contents of 2.5, 5, 7.5, and 10 m% were used to create differences in the carbon content in the green part. This induced a Co migration during the liquid phase sintering process. The sintering parameters were varied in time and temperature and studied regarding their effect on the microstructure and the porosity, the formation of the Co gradient, and the hardness. At low sintering times and temperatures, all carbon differences led to a Co gradient in the sintering part with a deviation of up to 10 m%. With an increase in sintering time and temperature, the Co distribution began to even out, and a deviation was observed only in the parts created with the inks containing 7.5 and 10 m% of particles. Hardness values of up to 1300 HV10 were obtained, which is comparable to conventionally produced WC–Co parts. The excess of carbon resulted in porosity in the parts leading to a reduced density. However, with inks containing 10 m% particles, densities of 94.26% were achieved at the longest sintering times and the highest temperature.

Fabrication of plasma-treated superhydrophobic polydimethylsiloxane (PDMS) – Coatėd melamine sponge for enhanced adhesion capability and sustainable oil/water separation

A persistent global issue is the need for developing novel absorbent materials with high absorption efficacy and rapid absorption rates for effective oil–water separation. This work presents a novel, resilient, and recyclable material with exceptional sorption capabilities, achieved through a simple surface modification of melamine sponge (MS) using Argon plasma treatment followed by Polydimethylsiloxane (PDMS) polymer coating (Ar-PT/PDMS@MS). This study also delineates the choiceful impact of atmospheric and vacuum plasma over the surface modification of MS. The material's super hydrophobicity, demonstrated by a high-water contact angle of ∼165°, is enhanced using novel plasma treatment to homogenously coat PDMS polymer. This treatment also imparts sturdiness to withstand harsh environmental conditions. The modified 3D networked structure of melamine sponge with a porous core was able to selectively absorb the oil of various densities with the capacity range of 42–139.5 mg/g. The batch and continuous O/W separation studies revealed the efficiency of the modified MS to be able to selectively separate light nonaqueous phase liquids (LNAPL) and dense nonaqueous phase liquids (DNAPL) oil with more than 99% efficiency. The continuous studies showed that using diesel oil the separation efficiency was >99% for 35 L of oil for more than 5 h. It was also discovered that it outperformed and exceeded commercial absorbent materials in terms of absorption capacity. The recyclability studies highlighted the ability of the modified MS to be used for more than 10 cycles without compromising its separation efficiency. These findings may foreshadow Ar-PT/PDMS@MS's ability to be a promising antagonist for oil–water (O/W) separation in real-world oil-spill scenarios.

Interface Engineering with Formamidinium Salts for Improving Ambient-Processed Inverted CsPbI3 Photovoltaic Performance: Intermediate- vs Post-Treatment.

Inverted all-inorganic perovskite solar cells (PSCs) have attracted increasing attention owing to excellent thermal stability, easy fabrication, and adaptable application as top cell in tandem solar cells. Apart from efficiency, ambient processing is desirable for practical production. To avoid water invasion in ambient air, surface engineering for perovskites is reported as a valid approach. However, most were performed by post-treatment, which hardly regulates the formation process of perovskite crystals. This work demonstrates a simple but effective surface intermediate-treatment strategy to stabilize CsPbI3 perovskites fabricated in ambient air and compares the different effects yielded on the inverted PSCs. By using formamidinium (FA) salts for intermediate-treatment, the strong interaction between FA cation and [PbI6]4- octahedron improves the moisture resistance, and compared with the post-treatment strategy, the accelerated crystallization rate and the shortened exposure time to moisture reduce the devastation by water during film fabrication process further. Moreover, the greatly passivated defects and optimized energy level matching between perovskite and PCBM suppress the nonradiative recombination. Resultantly, the optimized device shows enhanced efficiency from 11.39% to 15.45%, and long-term stability is improved, with 97.6% efficiency remaining after storage for 1600 h. Therefore, we believe that this work can provide a promising guideline for fabricating all-inorganic inverted PSCs in a low-cost manufacturing scheme.

Development of bioactive and antimicrobial nano-topography over selective laser melted Ti6Al4V implant and its in-vitro corrosion behavior

Additive manufacturing (AM) or 3D printing of bone defect models is gaining much attention in the biomedical field as it could significantly facilitate the development of customized implants with a high degree of dimensional accuracy. Due to their satisfactory biocompatibility and minimal stress shielding effect, Ti6Al4V (Ti64) alloys are increasingly preferred in the development of such implants. However, their poor osseointegration abilities and lack of antibacterial properties often cause implant loosening and microbial infections, leading to implant failure. To address these drawbacks, we propose in this work a simple surface modification approach of customized Ti64 alloys (3D printed Ti6Al4V) that enables the formation of porous calcium titanate (CT) over their surface as well as the incorporation of silver nanoparticles (AgNPs) into the thus formed porous network. The successful CT formation with the incorporation of AgNPs throughout the 3D printed Ti64 surface and their influence in changing the morphological and mechanical behaviour were studied by Raman spectroscopy, SEM, AFM, Contact angle measurement, XPS, HR-TEM and nano-indentation. Antibacterial studies using Staphylococcus aureus and Escherichia coli, and in-vitro cell studies using MG-63 cell lines showed that surface modified samples resulting from the proposed method exhibit satisfactory antimicrobial property and are highly biocompatible. The obtained surface modified samples also showed a significant improvement in corrosion resistance as compared to unmodified 3D printed Ti64 alloys. The improvement in corrosion resistance was revealed by electrochemical impedance Spectroscopy (EIS). Obtained results emphasis that thus surface modified 3D printed Ti64 alloys are promising candidates for hard tissue implant applications.

Bio-inspired polydopamine layer as a versatile functionalisation protocol for silicon-based photonic biosensors

Photonic biosensors have made major advances in recent years, achieving very high sensitivity, and progressing towards point-of-care deployment. By using photonic resonances, sensors can be label-free, which is particularly attractive for a low-cost technological realisation. A key remaining issue is the biological interface and the efficient and reliable immobilisation of binder molecules such as antibodies; many protocols are currently in use that have led to widely varying sensor performance. Here, we study a very simple and robust surface functionalisation protocol for silicon photonics, which is based on polydopamine, and we demonstrate both its simplicity and its high performance. The use of polydopamine (PDA) is inspired by molluscs, especially mussels, that employ dopamine to adhere to virtually any surface, especially in an aqueous environment. We studied the versatility of the PDA protocol by showing compatibility with 5 different disease biomarkers (Immunoglobulin (IgG), C-reactive protein (CRP), Tumour Necrosis factor-α (TNF-α), Interleukin-6 (IL-6), Matrix metalloproteinase (MMP-9) and show that the protocol is resistant to hydrolysis during incubation; the loss of functionality due to hydrolysis is a major issue for many of the functionalisation protocols commonly used for silicon-based sensors. The study using guided mode resonance-based sensors highlights the wide dynamic range of the protocol (0.01 ng/mL to 1 μg/mL), using IgG, CRP and MMP-9 protein biomarkers as exemplars. In addition, we show that the surface chemistry allows performing measurements in 10% human serum with a sensitivity as low as 10 ng/mL for IgG. We suggest that adopting this protocol will make it easier for researchers to achieve biofunctionalisation and that the biosensor community will be able to achieve more consistent results.

Polyvinyl chloride surface coated with polymer brushes using a chain‐transfer reaction for enhanced fouling resistance

AbstractThis study reports coating negatively charged polymer brushes covalently onto the surface of polyvinylchloride (PVC) using a simple conventional surface free‐radical polymerization technique with help of a chain transfer agent. The coated surfaces were assessed with contact angle, protein adsorption, cell adhesion and bacterial adhesion. Bovine serum albumin (BSA) and bovine fibrinogen (BFG) were used for protein adsorption evaluation. Mouse fibroblast (NIH‐3 T3) cells and Pseudomonas aeruginosa (P. aeruginosa) were used to assess cell and bacterial adhesion. Results show that the surface modified with all the attached polymer brushes exhibited significantly reduced contact angle, protein adsorption, and cell as well as bacterial adhesion, among which the negatively charged polymers showed the extremely low values in all the tests. The negatively charged polymer shows its contact angle at 4.6° as compared to 70° for original PVC. Its BSA, BFG, 3 T3 adhesion and P. aeruginosa adhesion were 93%, 84%, 92%, and 95% lower than original PVC. Furthermore, the PVC surface coated with negatively charged polymer brushes exhibited a hydrogel‐like property. The results indicate placing acrylic acids using a simple surface‐initiated free‐radical polymerization with help of a chain transfer agent onto PVC surface and then converting the acids to negative charges can be an affective and efficient route for fouling resistant applications.

Dimers, webs, and local systems

For a planar bipartite graph G \mathcal {G} equipped with an S L n \mathrm {SL}_n -local system, we show that the determinant of the associated Kasteleyn matrix counts “ n n -multiwebs” (generalizations of n n -webs) in G \mathcal {G} , weighted by their web-traces. We use this fact to study random n n -multiwebs in graphs on some simple surfaces.

Predicting Continental Scale Malaria With Land Surface Water Predictors Based on Malaria Dispersal Mechanisms and High-Resolution Earth Observation Data.

Despite malaria prevalence being linked to surface water through vector breeding, spatial malaria predictors representing surface water often predict malaria poorly. Furthermore, precipitation, which precursors surface water, often performs better. Our goal is to determine whether novel surface water exposure indices that take malaria dispersal mechanisms into account, derived from new high-resolution surface water data, can be stronger predictors of malaria prevalence compared to precipitation. One hundred eighty candidate predictors were created by combining three surface water malaria exposures from high-accuracy and resolution (5m resolution, overall accuracy 96%, Kappa Coefficient 0.89, Commission and Omission error 3% and 13%, respectively) water maps of East Africa. Through variable contribution analysis a subset of strong predictors was selected and used as input for Boosted Regression Tree models. We benchmarked the performance and Relative Contribution of this set of novel predictors to models using precipitation instead of surface water predictors, alternative lower resolution predictors, and simpler surface water predictors used in previous studies. The predictive performance of the novel indices rivaled or surpassed that of precipitation predictors. The novel indices substantially improved performance over the identical set of predictors derived from the lower resolution Joint Research Center surface water data set (+10% R 2, +17% Relative Contribution) and over the set of simpler predictors (+18% R 2, +30% Relative Contribution). Surface water derived indices can be strong predictors of malaria, if the spatial resolution is sufficiently high to detect small waterbodies and dispersal mechanisms of malaria related to surface water in human and vector water exposure assessment are incorporated.

Topic Modeling for Text Structure Assessment: The case of Russian Academic Texts

Background: Automatic assessment of text complexity levels is viewed as an important task, primarily in education. The existing methods of computing text complexity employ simple surface text properties neglecting complexity of text content and structure. The current paradigm of complexity studies can no longer keep up with the challenges of automatic evaluation of text structure.
 Purpose: The aim of the paper is twofold: (1) it introduces a new notion, i.e. complexity of a text topical structure which we define as a quantifiable measure and combination of four parameters, i.e. number of topics, topic coherence, topic distribution, and topic weight. We hypothesize that these parameters are dependent variables of text complexity and aligned with the grade level; (2) the paper is also aimed at justifying applicability of the recently developed methods of topic modeling to measuring complexity of a text topical structure.
 Method: To test this hypothesis, we use Russian Academic Corpus comprising school textbooks, texts of Russian as a foreign language and fiction texts recommended for reading in different grades, and employ it in three versions: (i) Full Texts Corpus, (ii) Corpus of Segments, (iii) Corpus of Paragraphs. The software tools we implement include LDA (Latent Dirichlet Allocation), OnlineLDA and Additive Regularization Of Topic Models with Word2vec-based metric and Normalized Pairwise Mutual Information.
 Results: Our findings include the following: the optimal number of topics in educational texts varies around 20; topic coherence and topic distribution are identified to be functions of grade level complexity; text complexity is suggested to be estimated with structural organization parameters and viewed as a new algorithm complementing the classical approach of text complexity assessment based on linguistic features.
 Conclusion: The results reported and discussed in the article strongly suggest that the theoretical framework and the analytic algorithms used in the study might be fruitfully applied in education and provide a basis for assessing complexity of academic texts.

Functionalized PCN-777-supported Lindqvist-type polyoxometalate derivatives for oxidative desulfurization: Role of electron-donating effect and hydrophobicity

The electronic structure and hydrophobicity of heterogeneous catalysts are of great importance to catalytic performance. A novel catalyst of functionalized PCN-777-supported Lindqvist-type polyoxometalate derivatives was designed and prepared. The hydrophobicity of the catalyst was improved by simple surface modification. The catalyst was applied in the ODS of dibenzothiophene (DBT) in this study, and the support and catalyst were characterized by Fourier transform infrared (FT-IR), contact angle test, and other methods. Systematic characterization and ODS experiments further confirmed the electron-donating effect of functionalized PCN-777 (tBu-PCN-777) with high hydrophobicity on [C12Py]3(NH4)3Mo7O24. The electron-donating effect leads to a narrow bandgap and high electron density of Mo active sites, ensuring that the catalyst [C12Py]3(NH4)3Mo7O24/tBu-PCN-777-35% exhibits excellent ODS activity. In particular, [C12Py]3(NH4)3Mo7O24/tBu-PCN-777-35% completely removed DBT at 60 °C in 50 min, and it continued to be stable after 30 cycles. The sulfur removal efficiency of real diesel oil reached 92.26%. This study demonstrates that functionalized PCN-777 has desulfurization potential and provides new ideas for increasing ODS catalytic activity from the design of electron-donating effect and hydrophobicity.

Longitudinal-optical-phonon resonant thermal emission efficiency and spectrum control of metal-GaAs surface micro-stripe structures

Phonon-based tera-Hertz or mid-infrared emission has been investigated because it can be applied to high-efficiency light sources for optical communication and material diagnostics, where thermal energy can be utilized as an energy source of emission. Particularly, nano- and micro-surface structures have been investigated for versatile emission controllability. We present the polarized longitudinal optical (LO) phonon resonant thermal emission of radiation (LORE) peaked at approximately 8.5 THz in a range of 450–650 K from simple surface Au–GaAs–Au micro-stripe structures on undoped (u-) GaAs wafers, where the metal component, which has been avoided for surface phonon polariton (SPhP) emission, is introduced. This LORE is based on electric dipoles formed by coherently oscillating polarization charges on pairs of interfaces and has a feature of structure size or emission direction-independent frequency, which is quite different from the properties of SPhPs. The dependence of emission properties on structural factors and temperature reveals the approximately evenly matched radiative and nonradiative LO-phonon annihilation rates in the local surface field and shows the controllability of emission and absorption balance based on the surface structures. Higher emission efficiency in the higher temperature region is found for structures with narrow emission windows of less than 2 μm. The decrease in the volume occupied by electric dipoles reduces the reabsorption probability of LORE, which shortens the effective radiative lifetime and, resultantly, increases the fraction of the radiative rate in the total annihilation rate. By comparing the emission from a pure graphite wafer, a short LORE mean time interval of approximately 2 ps is found. The background emission subject to Planck’s law is significantly reduced particularly in the region of 250–300 cm−1 using emission window widths narrower than 2 μm because of the sub-diffraction phenomenon.

Enhanced Antibacterial Activity at Ag-Cu Nanojunctions: Unveiling the Mechanism with Simple Surfaces of CuNPs-on-Ag Films.

Deposition of CuNPs on silver film gives rise to the formation of active Ag-Cu interfaces leading to dramatic enhancements in antibacterial activity against Escherichia coli. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDAX) analyses reveal that CuNPs are covered in a thin Cu2O shell, while X-ray photoelectron spectroscopy measurements (XPS) reveal that the Ag film samples contain significant amounts of Ag2O. XPS analyses show that the deposition of CuNPs on Ag films leads to the formation of a photoactive Ag2O-Cu2O heterostructure. Following a Z-scheme mechanism, electrons from the conduction band of Ag2O recombine with photogenerated holes from the valence band of Cu2O. Consequently, electrons at Cu2O's conduction band render Cu reduced and cause reductive activation of surface oxygen species on Cu forming reactive oxygen species (ROS). Interaction between metallic Cu and ROS species leads to the formation of a Cu(OH)2 phase. Both ROS and Cu(OH)2 species have previously been reported to lead to enhanced antibacterial properties. Holes on Ag2O produce a highly oxidized AgO phase, a phase reported to exhibit excellent antibacterial properties. Quantitative analysis of Cu and Ag high-resolution X-ray photoelectron spectroscopy (HR-XPS) spectra directly reveals several-fold increases in these active phases in full agreement with the observed increase in antibacterial activities. This study provides insight and surface design parameters by elucidating the important roles of Ag and Cu's bifunctionality as active antibacterial materials.

Banana pseudostem-inspired fluidic photothermal structure towards efficient solar steam generation and continuous salt rejecting

Solar-driven steam generation (SSG) is emerging as a promising off-grid strategy to relieve freshwater shortage. In recent years, extensive research works have been conducted to develop full biomass-based SSGs due to their unique hierarchical structural features. However, the long-term durability of biomass-based SSGs remains a concern. Herein, the discarded banana pseudostems have been demonstrated as an excellent potential SSG through a simple surface flame treatment. Firstly, the well-developed pore structure, superior light absorbance, extremely low thermal conductivity and superhydrophilic properties of the surface carbonized banana pseudostem (SCBP) have been well revealed respectively. In addition, it is also demonstrated that the SCBP evaporator can achieve an impressive evaporation rate of up to 2.548 kg·m−2·h−1 with a 91.96 % solar-thermal conversion efficiency superior to most reported biomass based SSGs. Furthermore, a SCBP inspired one-way fluidic photothermal structure is dedicatedly constructed. It is found that the salinity on the top surface of the SCBP evaporator remains far below 26 wt% and the evaporation rate is maintained at 2.384 kg·m−2·h−1 in a 15 wt% NaCl solution even after 200 h. Finally, from a proof-of-concept demonstration, the SCBP evaporator also shows an excellent water purification and seawater desalination performance in a real ocean situation.

Fire Risk of Polyethylene (PE)-Based Foam Blocks Used as Interior Building Materials and Fire Suppression through a Simple Surface Coating: Analysis of Vulnerability, Propagation, and Flame Retardancy

Building fires can spread through surface combustion of both combustible and interior finishing materials. Recently, the use of foam blocks as interior materials for high-rise residential buildings has increased. However, as foam blocks are primarily composed of polyethylene, they are not flame-retardant and can readily burn and the fire can spread, leading to large-scale damage. Herein, the fire hazard and diffusion characteristics of foam blocks were compared with those of flame-retardant and general wallpapers to confirm the risk of fire. The fire risk of the foam blocks was confirmed using flammability, cone calorimetry, and spread-of-flame analyses. Based on a comparative analysis of the fire risk of foam blocks, the average total heat release was 11.2 MJ/m. This is approximately three times higher than the average heat release rate of the flame-retardant wallpaper and approximately two times higher than that of the general wallpaper. The foam blocks ignited rapidly owing to fire and generated large amounts of combustion gas and heat. To prevent such a fire, 5 wt% montmorillonite (MMT) was simply coated after surface modification to suppress the occurrence of fire. Various flame-retardant materials, surface modifications, and fire safety systems must be developed to prevent fire hazards.

Unlocking the potential of 3D printed microfluidics for mass spectrometry analysis using liquid infused surfaces

Combining microfluidics with mass spectrometry (MS) analysis has great potential for enabling new analytical applications and simplifying existing MS workflows. The rapid development of 3D printing technology has enabled direct fabrication of microfluidic channels using consumer grade 3D printers, which holds great promise to facilitate the adoption of microfluidic devices by the MS community. However, photo polymerization-based 3D printed devices have an issue with chemical leeching, which can introduce contaminant molecules that may present as isobaric ions and/or severely suppress the ionization of target analytes when combined with MS analysis. Although extra cure and washing steps have alleviated the leeching issue, many such contaminant peaks can still show up in mass spectra. In this work, we report a simple surface modification strategy to isolate the chemical leachates from the channel solution thereby eliminating the contaminant peaks for MS analysis. The channel was prepared by fabricating a layer of polydimethylsiloxane graft followed by wetting the graft using silicone oil. The resulting liquid infused surface (LIS) showed significant reduction in contaminant peaks and improvement in the signal intensity of target analytes. The coating showed good stability after long-term usage (7 days) and long-term storage (∼6 months). Finally, the utility of the coating strategy was demonstrated by printing herringbone microfluidic mixers for studying fast reaction kinetics, which obtained comparable reaction rates to literature values. The effectiveness, simplicity, and stability of the present method will promote the adoption of 3D printed microdevices by the MS community.