Solid Surface Research Articles

Thermal and structural analysis of the DONES target system under steady state and transient loading conditions

One of the crucial steps in the European Roadmap to the realisation of fusion energy is the design and construction of the Demo-orientated NEutron Source (DONES) facility. DONES is a fusion-like neutron source, based on the International Fusion Materials Irradiation Facility (IFMIF) concept, aimed at qualifying and testing the materials to be used in fusion reactors. The Target System (TSY) is a crucial system as it is the component where the interactions between deuterons and a liquid lithium target, flowing on a solid surface (i.e. the Back Plate), take place to produce neutrons for irradiating the testing materials. In this regard, an investigation campaign has been performed to evaluate the thermo-mechanical behaviour of the DONES TSY under selected steady state and transient loading conditions, in light of the most recent design updates (new bellows and connection systems). The first part of the assessment concerned the analysis of the TSY under the normal operation steady state loading scenario. A detailed 3D FEM model has been set up, considering the newest updates of the TSY geometry and of the operational parameters, and a thermo-mechanical analysis has been launched. Results have been mainly checked in terms of TSY global deformation, focusing on the Back Plate and on the connecting bellows displacements, in order to exclude overlapping with the High Flux Test Module and misalignments with the beam footprint. Afterwards, since the lithium inlet temperature has been increased from 250 °C to 300 °C, a transient thermo-mechanical analysis of the TSY under the start-up loading conditions has been performed to check if it is able to withstand the hotter lithium flow according to the RCC-MRx criteria. Therefore, the reference pre-heating strategy has been adopted, assessing the thermal and mechanical behaviour of the TSY, focusing on the Back Plate. The obtained results are presented and critically discussed, suggesting important recommendations for the follow-up of the design.

Filtration System for Solid Surface Waste in Coastal Waters Based on Biomimicry and Circular Economy

One of the biggest environmental problems in the world is the inadequate disposal of solid waste in the oceans. Therefore, this article aims to demonstrate the importance of biomimicry and the circular economy in the development of a boat with peculiar characteristics of the filtration system existing in the mouth of the Whale Shark, which is capable of filtering surface solid waste in coastal waters, submerged at a depth up to two meters. Therefore, the basis for the research focused on studies published in books, articles, dissertations, websites, magazines relevant to the topic, taking into account the methodological process of product design. Finally, the importance of Biomimicry, Circular Economy and Design as strategic tools to find innovative solutions in order to mitigate environmental problems was verified.

On-The-Spot Sampling and Detection of Viral Particles on Solid Surfaces Using a Sponge Virus Sensor Incorporated with Finger-Press Fluid Release.

This paper presents a sponge-based electrochemical sensor for rapid, on-site collection and analysis of infectious viruses on solid surfaces. The device utilizes a conducting porous sponge modified with graphene, graphene oxide, and specific antibodies. The sponge serves as a hydrophilic porous electrode capable of liquid collection and electrochemical measurements. The device operation involves spraying an aqueous solution on a target surface, swiping the misted surface using the sponge, discharging an electrolyte solution with a simple finger press, and performing in situ incubation and electrochemical measurements. By leveraging the water-absorbing ability of the biofunctionalized conducting sponge, the sensor can effectively collect and quantify virus particles from the surface. The portability of the device is enhanced by introducing a push-release feature that dispenses the liquid electrolyte from a miniature reservoir onto the sensor surface. This reservoir has sharp edges to rupture a liquid sealing film with a finger press. The ability of the device to sample and quantify viral particles is demonstrated by using influenza A virus as the model. The sensor provided a calculated limit of detection of 0.4 TCID50/mL for H1N1 virus, along with a practical concentration range from 1-106 TCID50/mL. Additionally, it achieves a 15% collection efficiency from single-run swiping on a tabletop surface. This versatile device allows for convenient on-site virus detection within minutes, eliminating the need for sample pretreatment and simplifying the entire sample collecting and measuring process. This device presents significant potential for rapid virus detection on solid surfaces.

Spontaneous Wetting Induced by Contact-Electrification at Liquid-Solid Interface.

Wettability significantly influences various surface interactions and applications at the liquid-solid interface. However, the understanding is complicated by the intricate charge exchange occurring through contact electrification (CE) during this process. The understanding of the influence of triboelectric charge on wettability remains challenging, especially due to the complexities involved in concurrently measuring contact angles and interfacial electrical signals. Here, the relationship is investigated between surface charge density and change of contact angle of dielectric films after contact with water droplets. It is observed that the charge exchange when water spared lead to a spontaneous wetting phenomenon, which is termed as the contact electrification induced wetting (CEW). Notably, these results demonstrate a linear dependence between the change of contact angle (CA) of the materials and the density of surface charge on the solid surface. Continuous CEW tests show that not only the static CA but also the dynamics of wetting are influenced by the accumulation charges at the interface. The mechanism behind CEW involves the redistribution of surface charges on a solid surface and polar water molecules within liquid. This interaction results in a decrease in interface energy, leading to a reduction in the CA. Ab initio calculations suggest that the reduction in interface energy may stem from the enhanced surface charge on the substrate, which strengthens the hydrogen bond interaction between water and the substrate. These findings have the potential to advance the understanding of CE and wetting phenomena, with applications in energy harvesting, catalysis, and droplet manipulation at liquid-solid interfaces.

Bounce and contact mode regimes for drop impact on smooth surfaces: The influence of gas kinetics and electrostatics

When liquid drops impact on solid surfaces, an air layer forms in between the drop and the surface, acting as a cushion to mitigate the impact. In this work, we focus on delineating the bounce and contact mode regimes of impacting drops on smooth surfaces, specifically discerning whether drops rebound from the air layer or make contact with the solid surfaces, and pinpointing the precise contact modes between the drop and solid surfaces by resolving the gas film evolution and rupture. Our simulation model incorporates gas kinetics and electrostatics effects, both of which have been validated by experiments documented in the literature or theoretical models regarding thin film instabilities. We undertake a comprehensive review and categorization of the contact modes and elucidate how they change under different conditions of impact velocities, ambient pressures, and electric field intensities. We also provide some perspectives on the regime map for the lubricated surfaces, which contains an unresolved issue that the critical Weber number for bouncing-wetting transition is significantly reduced compared to the solid smooth surfaces like mica. These insights have noteworthy practical implications offering guidance for a wide range of scenarios, from normal-pressure environments to low-pressure conditions at high altitudes, encompassing high electric field conditions such as nanogenerators as well as low electric field conditions resembling glass surfaces with static electricity.

Area-selective atomic layer deposition (AS-ALD) of low temperature (300 °C) cobalt thin film using octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs)

As the semiconductor industry advances, manufacturing technologies encounter challenges in achieving precise alignment and thickness control with smaller and more intricate 3D structures. Addressing this, Area-selective atomic layer deposition (AS-ALD) emerges as a promising “bottom-up” approach, offering an alternative to current nano-patterning techniques. To achieve AS-ALD, self-assembled monolayers (SAMs) are employed as inhibitor agents. In this study, we employed plasma-enhanced atomic layer deposition (PEALD) to promote self-limiting surface reactions and enable low-temperature processing, thereby facilitating the implementation of high purity cobalt (Co) film through AS-ALD using octadecyltrichlorosilane (ODTS) SAM as an inhibitor. The selective deposition is achieved by employing SAMs as an inhibitor, belonging to the deactivation process, a common method for realizing a bottom-up approach. SAMs can form a thin organic film on a solid surface, allowing for surface modifications to become hydrophobic or hydrophilic. Through the selective deposition of Co in the PEALD low-temperature process (300 °C), we successfully addressed the degradation issue of ODTS SAM and verified the successful achievement of a high-purity selectively deposited 13.4 nm Co film. Our findings highlight the potential of selective Co deposition for realizing complex 3D structures and narrow interconnection layers.

Numerical study of porous tip treatment in suppressing tip clearance vortices in cavitating flow

Tip clearance cavitation (TCC) is a type of vortex cavitation. It widely exists in axial flow hydraulic machinery and has significant negative influence on the mechanical service life and the operating stability. It is necessary to suppress the tip clearance vortices (TCV) to control the TCC in engineering applications. Based on the analysis of the advantages and disadvantages of the present various suppression strategies, a new coupling method is proposed in this study by combining the damping approach and the diversion approach. Porous medium material is used to realize the coupling effect. A 2 mm span length porous tip is installed on the solid tip surface of a hydrofoil under two gap sizes conditions (representing two types of gap flow pattern), and excellent suppression results of the TCV and TCC are obtained. The characteristics and mechanism of the clearance flow are analyzed by numerical simulation. The numerical accuracy is verified by experimental qualitative observations. The simulation results show that the temporal and spatial stability of the clearance flow field is enhanced, and the leakage velocity and the TCV strength are weakened via the combined action of damping and diversion effects. There is a difference in the damping mechanism between the two gap flow patterns. It is a comprehensive result of viscous dissipation and momentum loss in the jet pattern represented by the small gap size, and primarily, the result of momentum loss in the rolling pattern represented by the large gap size.

Optimasi Adsorpsi Ion Tembaga (II) Menggunakan Silika Gel-GPTMS Termodifikasi Sulfonat

Adsorption is a process of sorption onto a specific substance that occurs at the surface of a solid material due to intermolecular forces or the penetration of a substance into the solid material surface. Adsorption involves an adsorbent as the sorbent material and an adsorbate as the component being sorbed. Silica gel is a commonly employed adsorbent for the sorption of Cu2+ ions. It is utilized as an adsorbent due to the presence of silanol and siloxane groups, which serve as active sites that can be modified. The modification aims to enhance the adsorption capacity of silica gel for Cu2+ metal ions. In aquatic environments, Cu metal ions are highly toxic to living organisms, posing significant hazards. The modifying compound employed in this study is monosodium salt of 4 – amino – 5 – hydorxy – 2,7 – naphthalenedisulfonic acid. However, prior to the sulfonate compound modification, a linking compound, γ-glycidoxypropyltrimethoxysilane (GPTMS), is required. The purpose of this study was to determine the effect of variations in pH and contact time on the adsorption of Cu2+ metal ions on sulfonate modified silica gel – GPTMS. The modified silica gel was characterized using Fourier-transform infrared (FTIR). The adsorption of Cu2+ ions was characterized by specific surface area (SSA), and the optimal adsorption conditions were determined as pH 4 and contact time of 60 minutes.

Electro-Thermopneumatically Actuated, Adhesion-Force Controllable Octopus-Like Suction Cup Actuator.

A light-weight actuator developed in this work belongs to a class of soft robots, and in a sense, resembles an octopus. Its main function is in the attachment or detachment to a solid surface driven by an electro-thermopneumatic mechanism. In this study, a suction cup similar to that of an octopus is manufactured from an elastomer, which is actuated by an electro-thermopneumatic system, mimicking the movement of the octopus' acetabular muscle. Accordingly, the adhesion force generated by such an actuator is regulated by releasing the inner air or adjusting the cup's elasticity. This actuator is designed to be an assistive device that facilitates the individual's physical strength in case of conditions related to aging or cerebellar disease, or a person who lost limbs. In this study, the actuator capabilities are demonstrated in the form of a grip-assisting glove and prosthetic attacher. Moreover, the adhesion mechanism is quantified by numerical simulations and verified experimentally.

Surface free energy calculation of the solid–fluid interfaces from molecular simulation

In this work, I present a straightforward approach for computing surface free energy γF based on the assessment of surface internal energy (γU), avoiding the difficulty connected to the determination of the elastic contribution in the case of a solid surface. This methodology has thus been extended to the calculation of γF for the interface between the liquid–vapor phase of water, the solid–vapor interface of aluminum, the aluminum–water interface, rigid graphene–water solid–liquid interfaces, and the n-dodecane–water liquid–liquid interface.

Alterations in paraffin wax crystal networks induced by asphaltenes and pour point depressants, investigated by atomic force microscopy

Wax crystallization in pipelines in cold environments is a key factor affecting flow assurance during crude oil production. Polar crude oil components, such as asphaltenes, and polymeric pour point depressants (PPDs) have been demonstrated to interact with wax during gelation and crystallization through complex formation during nucleation or crystal growth alteration which leads to co-crystallization. This study introduces a methodology based on atomic force microscopy (AFM) to characterize features of solid surfaces precipitated from model wax, wax-PPD, wax-asphaltene and asphaltene systems. Height data collected from AFM measurements enabled the quantification of modifications in crystal sizes and shapes induced by the presence of asphaltenes and PPDs. The 2D Fourier transform of the height was used to generate statistics for the frequency of height amplitude, revealing information about the pore size and the height patterns. A stiffness/elasticity analysis was used to calculate the Young Modulus of the upper layers. In wax and wax-asphaltene systems, two nano-scale layers with different Young Modulus profiles emerged. The nano-scale layer on the top was softer and corresponded to more amorphous wax crystal networks with trapped dissolved wax. The nano-scale layer on the bottom was stiffer, comprising of more crystalline structures, corresponding to wax crystals with lower deviations from full crystallinity, with properties independent of asphaltene concentration. A bilayer did not form in the presence of PPD, which prevented the formation of amorphous phases with trapped dissolved wax or gel. After a methodology for model systems was established, the focus moved to systems based on production wax i.e. recovered from deposits. This was complemented by a comparison between model precipitation conditions and precipitation by cold finger, resembling industrial processes. Results highlighted the effect of change in chemical composition on topography, elasticity and adhesion of the surface. AFM provided new insights into wax crystallization patterns in the presence of inhibitors, which can be used to quantify the extent of wax-inhibitor interactions and project it on production systems. The method could be used to explain macro-scale rheological properties of oils during flow assurance in the future.

Thermodynamic Properties of GaAs Solid Materials Extended to Surface Adsorption under External Magnetic Fields, Pressure, and Temperature

This research work instrumentalizes comprehensively the impacts of independent parameters like surface pressure, external magnetic field, and temperature on statistical thermodynamic quantities free energy, magnetization, occupied surface fraction, and equilibrium length. We approached it differently from a theoretical investigation conducted dealt with the behavioral dependence of surface parameters. Our mechanism was to investigate the interrelation between two dependent variables under exposure to two or more different independent parameters. Thus it seems complicated but it is used to probe surface information from the system at the same pace. We investigated the thermal excitation effect that leads to the detachment of the electron gas in contact with each occupied surface site, which reduces the adsorption of the surface in contrary external magnetic fields and pressure enhances the occupied surface probability of electrons to contact surface sites. Our findings reveal that the solid GaAs surface tends to capture electrons under the influences of external magnetic fields and pressure thus binding electrons and putting additional confining potential meanwhile the surface properties are affected. On the other hand surface, free energy has an inverse relation with magnetization, occupied surface fraction, in the case of equilibrium length it depended on the strong external magnetic fields.

Effect of Intermittent Low-Pressure Radiofrequency Helium Cold Plasma Treatments on Rice Gelatinization, Fatty Acid, and Hygroscopicity.

To establish the safe and reproducible effects of cold plasma (CP) technology on food products, this study evaluated the gelatinization parameters, fatty acid profile, and hygroscopic properties of rice grains repeatedly treated with low-pressure radiofrequency (RF) helium CP (13.56 MHz, 140 Pa, 120 W-20s, 0-4 times, and 300 g sample). Compared with the untreated (zero times) sample, with an increase in CP treatment times from one to four on rice, the water contact angle and cooking time decreased, while the water absorption rate and freshness index increased, and the pH value remained unchanged. CP repeating treatments essentially had no effect on the gelatinization enthalpy, but significantly increased the peak temperature of gelatinization. From the pasting profile of rice that has been repeatedly CP treated, the peak, breakdown, and setback viscosities in flour paste decreased. CP repeating treatments on rice did not change the short-range molecular order of starch. Compared with the untreated sample, the first helium CP treatment maintained the content of C18:1n9c, C18:2n6c, and C18:3n3, but the second to fourth CP treatment significantly decreased contents of these fatty acids (FAs) as the C18:0 content increased. The first three CP treatments can increase the water and sucrose solvent retention capacity in rice flours. CP repeatedly treated rice first exhibits the similar monolayer water content and solid surface area of water sorption. Principal component analysis shows that contact angle, pasting parameters, and fatty acid profile in milled rice are quite sensitive to CP treatment. Results support that the effect of low-pressure RF 120W helium CP treatment 20 s on rice grains is perdurable, and the improvement of CP intermittent treatments on rice cooking and pasting properties is an added benefit, and the hygroscopic properties of rice was kept.

Asphaltene Adsorption on Solid Surfaces Investigated Using Quartz Crystal Microbalance with Dissipation under Flow Conditions.

Asphaltenes can cause operational challenges in petroleum production facilities and adversely affect production by adsorption on mineral surfaces and alteration of the oil wettability of reservoirs. Therefore, understanding asphaltene adsorption mechanisms and their effects is crucial to improving the efficiency of oil production and reducing costs. In this study, we focus on understanding the impact of asphaltene concentration and the depositing environment of asphaltene adsorption on solid surfaces using the quartz crystal microbalance with dissipation (QCM-D) technique. The initial and long-term kinetics of adsorption at different concentrations were examined on three different solid surfaces including silicon dioxide to represent quartz mineral, stainless steel, and gold. The frequency-dissipation data showed evidence of monolayer adsorption initially, followed by multilayer formation. At short times, the adsorbed mass increased linearly with time, suggesting that the process was kinetically controlled rather than diffusion-controlled. The results were reproducible and did not depend on convection velocity but did depend on the surface material. At later stages, the monolayer development appeared to follow the random sequential adsorption (RSA) theory. Once multilayer adsorption commenced, the rates agreed well with the two-layer model of Zhu and Gu, 1990. The impact of asphaltene adsorption on the wettability of the surface was examined using contact angle studies, which showed decreasing water wettability with an increase in the adsorbed mass. The contact angle of water after 12 h of adsorption leveled off at around 100° on all three surfaces. Contact angle measurements were also used to evaluate if brine salinity causes the wettability alteration of surfaces with the adsorbed asphaltene. The results indicate that at 3% NaCl solution, the contact angle decreased only slightly by less than 2°.

Revisiting the wetting behavior of solid surfaces by water-like models within a density functional theory

We perform the analysis of predictions of a classical density functional theory for associating fluids with different association strength concerned with wetting of solid surfaces. The four associating sites water-like models with non-associative square-well attraction parametrized by Clark et al. [Mol. Phys., 2006, 104, 3561] are considered. The fluid-solid potential is assumed to have a 10-4-3 functional form. The growth of water film on the substrate upon changing the chemical potential is described. The wetting and prewetting critical temperatures, as well as the prewetting phase diagram are evaluated for different fluid-solid attraction strength from the analysis of the adsorption isotherms. Moreover, the temperature dependence of the contact angle is obtained from the Young equation. It yields estimates for the wetting temperature as well. Theoretical findings are compared with experimental results and in a few cases with data from computer simulations. The theory is successful and quite accurate in describing the wetting temperature and contact angle changes with temperature for different values of fluid-substrate attraction. Moreover, the method provides an easy tool to study other associating fluids on solids of importance for chemical engineering, in comparison with laboratory experiments and computer simulations.

Band Alignment of Oxides by Learnable Structural-Descriptor-Aided Neural Network and Transfer Learning.

The band alignment of semiconductors, insulators, and dielectrics is relevant to diverse material properties and device structures utilizing their surfaces and interfaces. In particular, the ionization potential and electron affinity are fundamental quantities that describe surface-dependent band-edge positions with respect to the vacuum level. Their accurate and systematic determination, however, demands elaborate experiments or simulations for well-characterized surfaces. Here, we report machine learning for the band alignment of nonmetallic oxides using a high-throughput first-principles calculation data set containing about 3000 oxide surfaces. Our neural network accurately predicts the band positions for relaxed surfaces of binary oxides simply by using the information on bulk structures and surface termination planes. Moreover, we extend the model to naturally include multiple-cation effects and transfer it to ternary oxides. The present approach enables the band alignment of a vast number of solid surfaces, thereby opening the way to a systematic understanding and materials screening.

Depinning of water droplets from a horizontal solid surface by wall-bounded shear flows

Depinning of water droplets from a horizontal solid surface by wall-bounded shear flows

Effect of viscosity on bubble spreading on flat solid surfaces

The behavior and dynamics of bubble spreading has a great impact on interfacial contact area and time, which is significant for the heat/mass transfer or separation efficiency. In this work, the dynamical behavior of bubble spreading especially the three-phase contact line (TPL) on solid flat surfaces in low viscous liquids was investigated. The results show that the final length of TPL on homogeneous solid surfaces tend to decrease with the increasing liquid viscosity. For heterogenous solid surfaces, TPL motion on non-stick coal surface is basically the same as that on homogeneous solid surfaces, whereas that on anthracite surface shows an anomalous morphology. By applying the power-law model, the fast and slow spreading stages of bubble on homogeneous surfaces show the universal exponent of b = 1/2 and b = 1/10, respectively. While the exponent for bubble spreading on heterogeneous surface is complicated due to the special surface physico-chemical properties.

Sandwich Immuno-RCA Assay with Single Molecule Counting Readout: The Importance of Biointerface Design.

The analysis of low-abundance protein molecules in human serum is reported based on counting of the individual affinity-captured analyte on a solid sensor surface, yielding a readout format similar to digital assays. In this approach, a sandwich immunoassay with rolling circle amplification (RCA) is used for single molecule detection (SMD) through associating the target analyte with spatially distinct bright spots observed by fluorescence microscopy. The unspecific interaction of the target analyte and other immunoassay constituents with the sensor surface is of particular interest in this work, as it ultimately limits the performance of this assay. It is minimized by the design of the respective biointerface and thiol self-assembled monolayer with oligoethylene (OEG) head groups, and a poly[oligo(ethylene glycol) methacrylate] (pHOEGMA) antifouling polymer brush was used for the immobilization of the capture antibody (cAb) on the sensor surface. The assay relying on fluorescent postlabeling of long single-stranded DNA that are grafted from the detection antibody (dAb) by RCA was established with the help of combined surface plasmon resonance and surface plasmon-enhanced fluorescence monitoring of reaction kinetics. These techniques were employed for in situ measurements of conjugating of cAb to the sensor surface, tagging of short single-stranded DNA to dAb, affinity capture of the target analyte from the analyzed liquid sample, and the fluorescence readout of the RCA product. Through mitigation of adsorption of nontarget molecules on the sensor surface by tailoring of the antifouling biointerface, optimizing conjugation chemistry, and by implementing weak Coulombic repelling between dAb and the sensor surface, the limit of detection (LOD) of the assay was substantially improved. For the chosen interleukin-6 biomarker, SMD assay with LOD at a concentration of 4.3 fM was achieved for model (spiked) samples, and validation of the ability of detection of standard human serum samples is demonstrated.

Hydrophobic Solid Photothermal Slippery Surfaces with Rapid Self-repairing, Dual Anti-icing/Deicing, and Excellent Stability Based on Paraffin and Etching.

Ice and snow disasters have greatly affected both the global economy and human life, and the search for efficient and stable anti-icing/deicing coatings has become the main goal of much research. Currently, the development and application of anti-icing/deicing coatings are severely limited due to their complex preparation, structural fragility, and low stability. This work presents a method for preparing hydrophobic solid photothermal slippery surfaces (SPSS) that exhibit rapid self-repairing, dual anti-icing/deicing properties, and remarkable stability. A photothermal layer of copper oxide (CuO) was prepared by using chemical deposition and etching techniques. The layer was then impregnated with stearic acid and solid paraffin wax to create a hydrophobic solid photothermal slippery surface. This solves the issue of low stability on superhydrophobic surfaces caused by fragile and irretrievable micro/nanostructures. In addition, the underlying photothermal superhydrophobic surface provides good anti-icing/deicing properties even if the paraffin on the surface evaporates or is lost during operation. The findings indicate that when subjected to simulated light irradiation, the coating's surface temperature increases to 80 °C within 12 min. The self-repair process is completed rapidly in 170 s, and at -15 °C, it takes only 201 s for the ice on the surface to melt completely. The surface underneath the paraffin exhibited good superhydrophobic properties, with a contact angle (CA) of 154.1° and a sliding angle (SA) of 6.8° after the loss of paraffin. Simultaneously, the surface's mechanical stability and durability, along with its self-cleaning and antifouling properties, enhance its service life. These characteristics provide promising opportunities for practical applications that require long-term anti-icing/deicing surfaces.