Liquid Contact Research Articles

Understanding the influence of fluid flow regime on plasma morphology and dose delivery at the plasma–liquid interface

Plasma-based water purification involves the transport of reactive species across the gas–liquid interface. This process is limited by slow diffusion driven mass transport of reactive species across the interface. Additionally, the plasma gas–liquid contact area is typically limited, contributing to reduced dose delivery. These key factors make it difficult to scale up the treatment process to input flows of industrial interest. In this work, turbulence is explored as a means to introduce a fine grain structure, thus greatly increasing the interfacial surface area, leading to large property gradients and more efficient mass transport. Such a fine scale structure can also enhance the local electric field. The test apparatus explored in this work is the packed bed reactor that places thin water jets into contact with plasma. It is theorized that introducing turbulence, via increasing Reynolds number in such thin jets, may enhance the effective plasma dose at fixed plasma power. In this work, changes in the flow regime, from laminar to turbulent, of water jets in a packed bed water reactor (PBR) configuration are investigated experimentally. Methylene blue dye, a model contaminant, was tested in the PBR to demonstrate enhanced treatment via reduced treatment times. Plasma surface morphology around the jets noticeably changed with the flow regime, and turbulent flow demonstrated a faster hydrogen peroxide uptake, along with slower temperature, electrical conductivity, and a pH change in a batch treatment process, compared to laminar flow. The dye was destroyed significantly faster in the turbulent flow, indicating an increased effective plasma dose.

The effect of volatile compounds of Syzygium aromaticum flower buds against Aspergillus flavus growth on wheat grain at postharvest stage

Reducing the postharvest loss of cereal grains caused by deleterious fungi is critically important for the grain supply chain. Exploring antifungal constituents of plant volatile organic compounds (PVOCs) could promote the development of natural gaseous fungicides in controlling the decay of postharvest grains. In this study, PVOCs were extracted from clove ( Syzygium aromaticum L.) buds and the primary constituents thereof were investigated for their effect on Aspergillus flavus growth in media postharvest grains. Fumigation with clove buds’ volatiles effectively inhibited A. flavus proliferation in 20% moisture wheat grains under simulated storage conditions. Gas chromatography-mass spectrometry analysis revealed that eugenol and caryophyllene were the two main constituents of clove bud volatiles (49.80% and 36.68%, respectively). An antifungal assay demonstrated that eugenol was responsible for the antifungal activity of clove bud volatiles against A. flavus. Eugenol can completely inhibit A. flavus growth at 0.12 and 0.40 μL/mL in vapor phase fumigation and liquid contact, respectively. The proliferation of A. flavus in 20% moisture wheat grains was completely controlled after fumigation with 600 μL/L eugenol vapor. Eugenol treatment can damage the membrane integrity of A. flavus mycelia, resulting in increased intracellular electrolyte leakage. The 38 metabolites in A. flavus hyphae exposed to 0.40 μL/mL eugenol were markedly differentially expressed and principally involved in the biosynthesis of glycerophospholipids, linoleic acid metabolism, fatty acid metabolism, sugar metabolism, and ATP-binding cassette transporters. Eugenol also causes phosphatidylserine eversion of the plasma membrane, increased reactive oxygen species, decreased ATP production, and damaged DNA in A. flavus . We propose that eugenol treatment can disrupt cell membrane integrity, fatty acid β -oxidation, and induce apoptosis in A. flavus . This study demonstrated the potential application of clove bud volatile organic compounds as biofumigants for postharvest grain management and provided new insights into the antifungal mechanism of the main constituents against A. flavus growth. • Clove volatiles from Syzygium aromaticum , L. could control Aspergillus flavus growth in wheat grains. • Eugenol and caryophyllene are the two main volatile components of clove determined by GC-MS. • Eugenol could inhibit the growth of A. flavus in vapor phase and liquid contact. • The antifungal actions of eugenol on A. flavus were studied by metabolomic and biochemical analyses. • Eugenol could be used as biofumigants for postharvest grain management.

Liquid Concentration Measurement Based on Liquid Contact Angle

Different concentrations of the same liquid or liquids with different solutes have different surface tensions. The macroscopic phenomenon is that they have different wetting effects on the same solid surface. The liquid contact angle can describe the wetting effect. Therefore, this paper proposes a method for measuring the liquid concentration using the liquid contact angle. A glass plate with a hydrophobic layer and an angle-measuring device forms the detection part. The glass plate is placed horizontally, and the solution to be tested is dropped on the surface of the glass plate. Solutions with different concentrations have different liquid-solid interfacial tension and liquid-gas interfacial tension, resulting in different liquid contact angles, which can achieve rapid and accurate measurement of solution concentration. Experiments show that the liquid contact angle of ethanol solution decreases with the increase of liquid concentration. Different volumes of ethanol solutions with the same concentration have substantially the same liquid contact angle. This experimental method has the advantages of being simple and easy to operate, having a wide range of applications, not easily limited by the type of detection solution, having a large concentration measurement range, having less sample usage, free from electromagnetic interference, and having real-time online detection.

Conversion of Marine Plastic Litter into Chemicals and Fuels through Catalytic Pyrolysis Using Commercial and Coal Fly Ash-Synthesized Zeolites

A marine plastic litter (MPL) sample, collected during a beach cleanup campaign, underwent thermal and catalytic pyrolyses to demonstrate that valuable hydrocarbon oil and gas can be produced from heterogeneous plastic waste, partly aged and not mechanically recyclable. A low-cost H-X zeolite lab synthesized from coal fly ash (CFA) was tested and compared with two commercial zeolites (H-USY and H-ZSM-5) commonly used in the industrial cracking field. MPL characterization revealed it is mainly composed of polyethylene and polypropylene (52 and 45 wt %, respectively), and it has ideal physicochemical properties as feed for pyrolysis processes. Thermogravimetric analyses demonstrated that catalysts can reduce the degradation temperature of MPL from 472 to 425 °C and from 450 to 421, 342, and 380 °C for H-ZSM-5, H-X/CFA, and H-USY, respectively. These results were confirmed by thermal and catalytic pyrolyses tests performed in a bench-scale reactor. All the catalytic tests were carried out at 450 °C with a liquid phase contact mode. In particular, H-X/CFA, avoiding tar and wax formation, produced up to 87 wt % of light oil with a high content of short chain aliphatic hydrocarbons, obtaining results very similar to those gained with the expensive commercial H-USY. For all the catalytic pyrolysis tests, the produced gases proved to be more than sufficient to sustain the process heat requirement.

Wettability State Transition and Interfacial Slip Analysis of the Hydrophobic Nanostructure Surface Controlled by an Electric Field

Superhydrophobicity is widely used for reducing drag in pipeline transportation and preventing corrosion of metals. Interfacial slip is the leading factor of hydrophobic surface drag reduction. The presence of a gas–liquid interface is determined by the wetting state of a liquid on the surface. Therefore, investigating the influence of the wetting state on the interfacial slip is essential. In this study, an electric field was used to control the wetting state of a hydrophobic surface. Microchannel and micro-particle image velocimetry technologies were simultaneously used to investigate the effect of different wetting states on interfacial slip characteristics and to explore the mechanism of influence of these wetting states. As the performance changed from the Cassie contact state to the Wenzel contact state, the gas–liquid contact interface gradually moved downward and the interface slip weakened. The Wenzel contact state was achieved by filling the liquid to the bottom of the structure, and the gas–liquid interface and the interface slip disappeared. Consequently, the hydrophobic surface lost the drag reduction effect.

Suppression of wetting transition on evaporative fakir droplets by using slippery superhydrophobic surfaces with low depinning force

This study experimentally investigated the evaporation and wetting transition behavior of fakir droplets on five different microstructured surfaces. Diamond-like carbon was introduced as the substrate, and the influence of varying the width, height, and pitch of the micropillars was assessed. The experimental results showed that the interfacial properties of the surfaces change the evaporation behavior and the starting point of the wetting transition. An important result of this study is the demonstration of a slippery superhydrophobic surface with low depinning force that suppresses the transition from the Cassie–Baxter state to the Wenzel state for microdroplets less than 0.37 mm in diameter, without employing large pillar height or multiscale roughness. By selecting an appropriate pillar pitch and employing tapered micropillars with small pillar widths, the solid–liquid contact at the three-phase contact line was reduced and low depinning forces were obtained. The underlying mechanism by which slippery superhydrophobic surfaces suppress wetting transitions is also discussed. The accuracy of the theoretical models for predicting the critical transition parameters was assessed, and a numerical model was developed in the surface evolver to compute the penetration of the droplet bottom meniscus within the micropillars.

Experimental investigation and comparative analysis of immersion cooling of lithium-ion batteries using mineral and therminol oil

Renewable energy can potentially mitigate the adverse effects of energy and environmental crises. The Lithium-ion battery, a storage system investigated in the present study, has a potential to increase the penetration of renewable energy technologies, due to its high mass and volumetric energy density. However, thermal management strategies are necessary for lithium-ion battery electrical storage to grow technologically and gain widespread acceptability. In the present work, a comparative study of the different cooling methods, namely, forced air cooling (FAC), direct liquid contact cooling (i.e., Mineral oil cooling (MOC), and therminol oil cooling (TOC)) with low-cost coolants have been carried out on 20 cells of 10Ah lithium-ion battery-stack at a discharge rate of 1C, 1.5C, 2C, 2.5C, and 3C. It is found that the maximum temperature of the battery module is reduced by 43.83%, 49.17%, and 51.54% for forced air cooling, therminol oil cooling, and mineral oil cooling respectively, at 3C discharge rate, compared to the natural air-cooling method.Under the experimental conditions studied, the maximum temperature of the battery pack is found to be within the desired value during forced convection cooling only up to 1.5C discharge rate, while the immersion cooling performed satisfactorily up to 2C discharge rate. This study demonstrates direct liquid contact cooling with low-cost dielectric fluids as a safe and efficient thermal management technology for high-energy density and high-current lithium-ion battery applications.

Molecular dynamics study of the wettability effect on the evaporation of thin liquid sodium film

The nanoscale liquid sodium film exists in the porous wick of the sodium heat pipe. Understanding its evaporation is essential for further exploring the heat transfer inside the heat pipe. Due to the solid–liquid interaction, surface wettability has significant effects on evaporation. In this work, molecular dynamics is adopted to study these effects. A cuboid evaporation system is constructed. It consists of the bottom solid surface and thin liquid sodium film. By changing the potential well depth between solid and liquid atoms, four surfaces with different wettability are built. The 400 K equilibrium evaporation is achieved. The self-diffusion coefficients of liquid atoms on four surfaces are acquired. The non-equilibrium is introduced by increasing the heat source wall’s temperature to 600 K. The main phase of evaporation is in 0–8 ns. The variation of gas atoms number is observed. The evaporation rate, average heat flux, and heat transfer coefficient are acquired. The results indicate that evaporation could be improved with surface wettability. For the 0°, 58° hydrophilic surface, the heat transfer efficiency could reach 96.9 %, 96.3 % respectively. The surface wettability effects are achieved by two paths: it enhances the heat transfer in the solid–liquid contact region and intensifies the atoms’ collision heat transfer inside the liquid film.

Level Set Simulation on Single Wafer Wet Processing Improvement

To improve the single wafer process for wafer edge yield performance, the liquid film thickness is the key indicator to be investigated. The traditional measurement of liquid film thickness is difficult to execute, due to wafer spinning. The numerical method becomes essential to simulate the process. This paper uses the multiple flow level set method to simulate single wafer spin process. An inlet hydraulic jump is approximated by a two-dimensional axisymmetric approach with a collar inlet. Various spin rotation speeds, variable flow rates, different liquid types and contact angles are simulated. The results indicate liquid film discontinuity at a certain radius and a lower shear rate at the wafer edge. After modifying the process recipe based on the level set simulation result, the wafer edge yield shows improvement. This level set simulation model provides useful information for single wafer wet process control. The level set simulation results can estimate the liquid distribution on the wafer surface before the real process and can avoid experiments on production wafers and hence lead to a lower cost.

A review of droplet bouncing behaviors on superhydrophobic surfaces: Theory, methods, and applications

The phenomenon of droplet bouncing on superhydrophobic surfaces has received extensive attention in the academic and industrial fields, as it is critical for various engineering applications, such as anti-icing, spray cooling, and metal quenching. In this review, the research of droplet bouncing behaviors is comprehensively introduced from the bouncing mechanism, research methods, and potential applications. The bouncing mechanism is related to three aspects: droplet properties, surface characteristics, and ambient conditions. Among them, droplet size, impact velocity, gas film, surface morphology, surface temperature, and applied electric field are frequently concerned. Surface wettability is critical for droplet bouncing behaviors, which affects the droplet movement on the surface. Momentum and mass distribution are essential to reduce contact time, which can be achieved through the surface morphology design. The manipulation of solid–liquid contact lines and surface tension can achieve directional droplet transportation. In addition, typical droplet bouncing experiments are presented, and experimental studies of single and successive droplets in recent decades are collated. Volume of fluid, the lattice Boltzmann method, and molecular dynamics are described, which are typical simulation methods for droplet bouncing dynamics at different scales. Potential engineering applications such as surface self-cleaning, digital microfluidics, and enhanced heat transfer have been developed through theoretical foundations and research methods. Finally, the conclusions and the possible future research directions are outlined. The durability of superhydrophobic surfaces becomes a bottleneck for engineering applications. The life cycle research perspective may be applied to future studies.

Experimental Study of Unsteady Drag Coefficient of Droplets in a Liquid–Liquid System

In liquid–liquid contact process, the motion of droplets relative to the surrounding fluid always involves accelerating and decelerating, which affects the mass, heat, and momentum transfer. The lack of experimental data of the unsteady drag coefficient has been one of the limitations on the prediction of the unsteady flow field. In this study, the accelerated and decelerated water droplets in an organic phase were measured by a high-speed camera. The results show that with a decrease in droplet diameter, the acceleration becomes more significant, while the absolute relative velocity decreases, causing a lower Reynolds number. The Basset force and add mass force were solved numerically and compared with drag force. The unsteady drag coefficient is always smaller than the corresponding steady drag coefficient in the case of accelerating relative flow and larger than that in the case of decelerating relative flow. A new unsteady drag coefficient model has been established, which has an acceptable agreement with the experimental data.

An Efficiently Doped PEDOT:PSS Ink Formulation via Metastable Liquid-Liquid Contact for Capillary Flow-Driven, Hierarchically and Highly Conductive Films.

With commercial electronics transitioning toward flexible devices, there is a growing demand for high-performance polymers such as poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS). Previous breakthroughs in promoting the conductivity of PEDOT:PSS, which mainly stem from solvent-treatment and transfer-printing strategies, remain as inevitable challenges due to the inefficient, unstable, and biologically incompatible process. Herein, a scalable fabrication of conducting PEDOT:PSS inks is reported via a metastable liquid-liquid contact (MLLC) method, realizing phase separation and removal of excess PSS simultaneously. MLLC-doped inks are further used to prepare ring-like films through a compromise between the coffee-ring effect and the Marangoni vortex during evaporation of droplets. The specific control over deposition conditions allows for tunable ring-like morphologies and preferentially interconnected networks of PEDOT:PSS nanofibrils, resulting in a high electrical conductivity of 6,616Scm-1 and excellent optical transparency of the film. The combination of excellent electrical properties and the special morphology enables it to serve as electrodes for touch sensors with gradient pressure sensitivity. These findings not only provide new insight into developing a simple and efficient doping method for commercial PEDOT:PSS ink, but also offer a promising self-assembled deposition pattern of organic semiconductor films, expanding the applications in flexible electronics, bioelectronics as well as photovoltaic devices.

Agglomeration behavior of the dense medium in a gas–solid separation fluidized bed

In this study, the atomic force microscopy (AFM) was used to measure the micro-forces between different particles and study the influence of different operating parameters on the formation of particle clusters in the gas–solid fluidized bed separation process. In this way, the mechanism of liquid bridge formation and fracture can be elucidated, thereby providing a theoretical basis for inhibiting the formation of particle clusters. The results indicated that for relative humidity (RH) < 40%, the extrusion liquid bridge is the dominant factor for the formation of the particle liquid bridge, and the liquid film thickness, h, and liquid film volume, Vsq, vary linearly with RH; however, once the RH is > 40%, these relationships become nonlinear. The adhesion force between magnetite powder particles was found to be the largest and that between pulverized coal particles was found to be the smallest, with the mixture of the two particle types being in between. Further, the adhesion between particles increased monotonically with RH, while showing a maximum value with increasing particle separation. A theoretical analysis of the critical fracture distance, Drupture*, of the particle liquid bridge showed that, as the liquid bridge volume, V*, and contact angle, θ, increase, Drupture* gradually increases, but its rate of increase rate. The theoretical analysis was found to be largely consistent with the experimental data, only deviating at low RH.

Numerical simulation and experimental studies on the ammonia absorption process by water injection in reaction effluent air cooler system

Water injection to dissolve ammonium salts and absorb crystallized gas components is an essential method to protect hydrogenation equipment against corrosion in refineries. The complex water-injected absorption process of NH3 is achieved by the Euler-Lagrange method, and in-situ experiments conducted under various operating conditions are utilized to validate it. The results indicate that the increase in velocity will raise the mass transfer coefficient slightly, however, the contact time between gas and liquid is shortened and decrease the efficiency of ammonia absorption. The area of gas–liquid contact increases as water flow rate rises, increasing the efficiency of ammonia absorption. The ammonia absorption efficiency initially increases and subsequently decreases when the water temperature rises from 290 K to 310 K. In addition, the ammonia absorption efficiency for the forward injection way is 10 %-15 % higher than that of the backward injection way at the same inlet velocity. The results of this work can provide theoretical guidance for the design optimization of the water injection process in refineries.

Solid–liquid contact TENG using a melting near-field direct writing PCL nano-fiber structure

ABSTRACT Recently, the triboelectric nanogenerator (TENG) has been widely studied for the development of flexible and wearable electronics. Among the various methods for TENG modification, melting near-field direct writing is a new method to fabricate solid-liquid TENG. Here, the electrospun PCL was introduced with traditional polymers to fabricate the compound solid triboelectric layer, and water, dimethicone and GaIn were chosen as the liquid triboelectric layers. In this paper, the solid substrate effect, temperature gradient effect, and the liquid substrate effect were compared in terms of TENGs. A free-standing model of TENG is employed in this paper, and the charge generated by the PCL-PI composite solid triboelectrical solid layer is more than 10 times higher than the pristine one, showing the high charge generating ability to melt near-field direct written microfibers. Furthermore, detailed investigation will be discussed how we can get a high the out-circuit voltage and short-circuit current.

Probing Contact Electrification between Gas and Solid Surface

Contact electrification exists everywhere and between every phase of matter. However, its mechanism still remains to be studied. The recent triboelectric nanogenerator serves as a probe and provides some new clues about the mechanism present in solid–solid, solid–liquid, and liquid–liquid contact electrification. The gas–solid model still remains to be exploited. Here, we investigated the contact electrification between gases and solids based on the single-electrode triboelectric nanogenerator. Our work shows that the amount of transferred charges between gas and solid particles increases with surface area, movement distance, and initial charges of particle increase. Furthermore, we find that the initial charges on the particle surface can attract more polar molecules and enhance gas collisions. Since ions in gas–solid contact are rare, we speculate that gas–solid contact electrification is mainly based on electron transfer. Further, we propose a theoretical model of gas–solid contact electrification involving the gas collision model and initial charges of the particle. Our study may have great significance to the gas–solid interface chemistry.

Numerical study of liquid imbibition and contact line pinning in a sealing gap for corrosion protection of metal housings

Numerical study of liquid imbibition and contact line pinning in a sealing gap for corrosion protection of metal housings

Tailoring thermal behavior and solid–liquid contact area of Sn/Cu composite solder during ultrasonic-assisted transient liquid phase process

Tailoring thermal behavior and solid–liquid contact area of Sn/Cu composite solder during ultrasonic-assisted transient liquid phase process

Research on influencing factors and remedial measures of coal seam water blocking effect

Coalbed methane development primarily relies on hydraulic fracturing and drainage gas extraction processes. The intrusion of external fluids and long-term drainage and extraction contribute to the water blocking effect, which becomes one of the crucial factors affecting production capacity. In this study, the coal reservoir of a certain coalbed methane in Hancheng, Shaanxi Province, was selected as the research object. The experimental method was employed to comprehensively evaluate the correlation between factors such as coal sample moisture content, permeability, porosity, properties of external liquids, and water blocking damage. The results indicated that there was a positive correlation between coal sample moisture content, liquid surface tension, and water blocking damage. On the other hand, coal sample pore permeability characteristics, liquid contact angle with rock samples, and water blocking damage showed a negative correlation. Building upon the aforementioned research, an investigation into remedial measures for water blocking damage was conducted. Additionally, a chemical treatment study using the compound surfactant system JSS-1 as a water-blocking agent was performed to manage the water blocking effect. The results demonstrated that JSS-1 as a water-blocking agent significantly reduced the surface tension of the wellbore fluid and improved its wetting behavior on the coal-rock surface. The laboratory experiments confirmed the capability of JSS-1 in managing the water blocking effect.

Design of screen-printed potentiometric platform for sensitive determination of mirabegron in spiked human plasma; molecular docking and transducer optimization.

The integration of molecular modelling simulation and electrochemical sensors is of high interest. Herein, for the first time, a portable solid-contact potentiometric electrode was designed for the sensitive determination of mirabegron (MIR) in human plasma and pharmaceutical formulation. A two-step optimization protocol was investigated for the fabrication of an ion on sensing polymeric membrane. First, molecular docking was used for optimum ionophore selection. Calix[6]arene showed the highest affinity towards MIR with a better docking score (-4.35) and potential energy (-65.23) compared to other calixarene derivatives. Second, carbon nanotubes and gold nanoparticles were investigated as ion-electron transducers using a drop-casting procedure. Gold nanoparticle-based sensors showed better slope, potential stability, and rapid response compared to carbon nanotubes. The proposed solid contact sensors (V-VII) showed comparable sensitivity and ease of handling compared to liquid contact sensors (I-IV). The optimized gold nanoparticles sensor VII produced a Nernstian response over the range of 9.77 × 10-7 to 1 × 10-3 M with LOD of 2.4 × 10-7 M. It has also been used to determine MIR in its pharmaceutical formulation in the presence of a co-formulated antioxidant butylated hydroxytoluene and spiked human plasma. This would offer a feasible and economic platform for monitoring MIR in pharmaceutical preparation and biological fluids.