Liquid Behavior Research Articles

Studies on PVP-Based Hydrogel Polymers as Dressing Materials with Prolonged Anticancer Drug Delivery Function.

Tamoxifen is a well-known active substance with anticancer activity. Currently, many investigations are performed on the development of carriers that provide its effective delivery. Particular attention is directed toward the formation of cyclodextrin-drug complexes to provide prolonged drug delivery. According to our knowledge, carriers in the form of polyvinylpyrrolidone (PVP)/gelatin-based hydrogels incorporated with β-cyclodextrin-tamoxifen complexes and additionally modified with nanogold have not been presented in the literature. In this work, two series of these materials have been synthesized-with tamoxifen and with its complex with β-cyclodextrin. The process of obtaining drug carrier systems consisted of several stages. Firstly, the nanogold suspension was obtained. Next, the hydrogels were prepared via photopolymerization. The size, dispersity and optical properties of nanogold as well as the swelling properties of hydrogels, their behavior in simulated physiological liquids and the impact of these liquids on their chemical structure were verified. The release profiles of tamoxifen from composites were also determined. The developed materials showed swelling capacity, stability in tested environments that did not affect their structure, and the ability to release drugs, while the release process was much more effective in acidic conditions than in alkaline ones. This is a benefit considering their use for anticancer drug delivery, due to the fact that near cancer cells, there is an acidic environment. In the case of the composites containing the drug-β-cyclodextrin complex, a prolonged release process was achieved compared to the drug release from materials with unbound tamoxifen. In terms of the properties and the composition, the developed materials show a great application potential as drug carriers, in particular as carriers of anticancer drugs such as tamoxifen.

Unrestricted Horizon Predictive Controller Applied in a Biphasic Oil Separator under Periodic Slug Disturbances

Multi-phase flow, characterised by the presence of both liquid and gas phases, often occurs in riser pipes during oil extraction. These flows can be problematic because they can cause oscillations due to the formation of bubbles within the pipes, which can negatively impact the safety and efficiency of offshore production operations. One solution to this problem is to use a gravitational oil separator, which is designed to dampen these oscillations. The separator is equipped with a control system that uses liquid level and gas pressure sensors to stabilise the flow by adjusting the positions of its valves. This paper presents the use of a specific type of model-based predictive controller to control the level and pressure of a biphasic oil separator, particularly in the presence of slug disturbances. The designs of the separator model and controller are discussed in detail, with a focus on the advantages of using an unrestricted horizon predictive controller, such as its ability to make predictions over a long horizon and its relatively low computational requirements. For the sake of comparison, a linear quadratic regulator is also evaluated. The simulation results demonstrate that the proposed control system is able to effectively regulate the separator’s liquid level and gas pressure within a magnitude range of 10−4 m for the liquid level and 10−3 bar for the internal pressure. Aside from that, the dynamics of the closed-loop system is six times faster than the plant’s for the liquid behaviour and 30 times faster for the pressure, while also presenting sharp attenuation characteristics for the input disturbances of nearly 50 dB for the pressure output and 68 dB for the liquid level.

Interfacial Features Govern Nanoscale Jumping Droplets

The solid surfaces with different profile levels impact the liquid-solid contact nature and hence wetting characteristics, showing a vital role in liquid droplets' mobility and dynamic behaviors. Therefore, engineering nanostructured features ultimately enables tuning and controlling the dynamic motion of droplets. In this study, we demonstrate an approach to manipulate nanodroplets' motion behaviors in contact with a surface through tailoring the surface morphological profile. By tracking the trajectories of water molecules at the interface, we find that the motions of a nanodroplet subjected to different levels of lateral force reveal various modes that are identified as creeping, rolling, and jumping motions. Interestingly, the elastic deformation of the droplet and sudden changes in the receding contact angle provide the mechanistic origin for droplet jumping. Guided by computational simulations, a regime map delineating the droplet motion modes with surface profile levels and applied forces is constructed, providing a design strategy for controlling droplet motions via surface engineering.

Visualization of Gas-Liquid Interfacial Behavior in a Narrow Channel Using High-Speed Neutron Imaging

Gas-liquid two-phase flow is a very complicated flow phenomenon that involves the interaction between gas and liquid phases. Recently, an accurate simulation technique of two-phase flow has been developed. However, the validation of the simulated results is insufficient due to less experimental data. It is especially difficult to measure interfacial behavior with significant spatio-temporal fluctuation. To understand such phenomena, measurement methods with high spatial and temporal resolutions are required. Neutron imaging is a powerful tool for two-phase flow visualization. It can be applied to flow measurement in an opaque channel and has applicability to the heated condition. In this study, two-phase flow in the narrow rectangular channel was visualized by high-speed neutron imaging. The dynamics of the interfacial structure of air-water flow were investigated from the neutron transmission images, and the liquid film behavior was observed qualitatively.

Adsorbate/adsorbent interactions in microporous zeolites: mechanistic insights from NMR relaxation and DFT calculations

Nuclear magnetic resonance (NMR) relaxation is an effective and non-invasive technique for probing guest-host interactions in porous materials. In particular, the ratio of longitudinal-to-transverse nuclear spin relaxation time constants T1/T2 has been demonstrated as a robust indicator of adsorbate/adsorbent interactions in mesoporous media. However, the use of NMR relaxation times in microporous materials to probe interactions and dynamics remains relatively unexplored. Herein, we investigate and describe the effect of the aluminium content in microporous HZSM-5 zeolites on the NMR relaxation times of a range of common liquid probe molecules. In particular, we discuss the NMR relaxation time behavior of liquids with hydrophilic (water, methanol) and hydrophobic (toluene, methyl cyclohexane) properties adsorbed over HZSM-5 samples with varying silica-to-alumina ratios (SAR = SiO2/Al2O3). Our results demonstrate that highly polar molecules show high sensitivity to aluminium content (i.e., surface acidity), with T1/T2 ratios increasing significantly for higher acidity zeolites. Conversely, for molecules with low polarity, the T1/T2 ratio as a function of SAR remains approximately constant, and in the zeolites with low SAR is much lower compared to that of water and methanol. Density functional theory (DFT) calculations are employed to contrast the surface interaction mechanisms of water and toluene within model zeolite structures of varying SAR, and provide molecular level insights into the observed trends in NMR relaxation behavior.

Spreading of water microdroplets simulating human sweating in polyester yarns and fabrics

Thermo-physiological comfort of human body is highly influenced by the moisture transmission behaviour of the fabric. For active sportswear, intimate apparels and inner layer of extreme cold weather clothing, moisture transport is very crucial. The liquid moisture transport of fabrics is analysed using standardised test methods like vertical wicking, absorbency test and moisture management through moisture management tester. These test methods use large reservoir of liquid in contrast to human sweating behaviour. The human skin generates sweats in the form of microdroplets through sweating glands. Hence, the standard test procedures employed to assess the fabric’s liquid moisture transport fail to capture preciously the sweat transport from human skin to the fabrics. Hence, in this work, the spreading behaviour of water microdroplets simulating human sweat through yarns which are the building block of fabrics and knitted fabrics that are widely used as sportswear or inner layer of extreme cold weather clothing are investigated. The purpose of this study is to understand how the microfluid move along the capillary channels in yarns (in the forms of network of yarns crossing over each other and fabric) by keeping yarn count and twist same for all yarns. A single micro drop representing accumulated sweat droplets and multiple drops showing continuous sweating through sweat glands were allowed to wick through the yarns made up of coarser and finer fibres to understand the role of fibre diameter on wicking kinetics. Results from the conventional wicking test were compared with microfluidic wicking. It is found that the initial wicking speed in coarser-fibres yarn is faster in comparison to finer-fibres yarn, but the final wicking height is longer in finer fibre yarn. Overall liquid spreading length found to be similar for both the yarns. Yarn to yarn liquid transfer at crossover junctions is faster with finer-fibre yarn compared to coarser-fibre yarn. Same trends are found in fabrics constructed with these yarns. The effect of yarn tortuosity on liquid spreading behaviour has also been studied. As the yarn path becomes torturous (straight yarn to fabric form) wicking length also decreases.

Confined ionic liquids films under shear: The importance of the chemical nature of the solid surface.

Ionic liquids have generated interest in applications as lubricants and as additives to conventional lubricants due to their unique physical properties. In these applications, the liquid thin film can be subjected simultaneously to extremely high shear and loads in addition to nanoconfinement effects. Here, we use molecular dynamics simulations with a coarse-grained model to study a nanometric film of an ionic liquid confined between two planar solid surfaces both at equilibrium and at several shear rates. The strength of the interaction between the solid surface and the ions was changed by simulating three different surfaces with enhanced interactions with different ions. The increase in the interaction with either the cation or the anion leads to the formation of a solid-like layer that moves alongside the substrates; however, this layer can exhibit different structures and stability. An increase in the interaction with the high symmetry anion produces a more regular structure that is more resistant to the effects of shear and viscous heating. Two definitions were proposed and used for the calculation of the viscosity: a local definition based on the microscopic characteristics of the liquid and an engineering definition based on the forces measured at the solid surfaces, with the former displaying a correlation with the layered structure induced by the surfaces. Because of the shear thinning behavior of the ionic liquids as well as the temperature rise brought on by viscous heating, both the engineering and the local viscosities decrease as the shear rate increases.

Efficient thermal energy storage achieved by NaCl–CuO composite phase change material: A molecular dynamics study

In this paper, NaCl–CuO based composite phase change material (CPCM) was proposed based on the composite material design strategy, and the microstructure model was designed. The microscale solid–liquid interface behavior during phase transition was investigated by observing the dynamic evolution of microstructure at nano scale. The thermal properties were obtained by means of molecular dynamics (MD) simulations. The simulation results were proven to have desired accuracy compared with available experimental values, and as the mass fraction of nano CuO increases from 0 to 1.6 wt% and 8.3 wt%, the shear viscosity was increased by 4.43 % and 8.12 %, and the thermal conductivity was increased by 5.45 % and 9.51 % on average in the temperature range of 800 K to 1500 K, respectively. The specific heat capacity was increased with a maximum value of 2.07 %, but the melting enthalpy was decreased by the maximum of 18.77 %. The results indicated that doping CuO into NaCl significantly increases the potential energy between atoms, so that desired thermal performance was achieved, which is mainly induced by the increase of coulomb interaction, bond stretching energy and bond bending energy. The results are expected to be helpful for further efficiency improvement of solar thermal energy utilization.

The behavior and mechanism of a temperature-responsive ionic liquid and its applications in extracting geniposidic acid from Eucommia ulmoides male flowers

A lower critical solution temperature responsive ionic liquid (IL) was fabricated via the neutralization reaction of tetrabutyl phosphine hydroxide ([P4444]OH) and benzimidazole (BzIm) for the ultrasonic extraction of geniposide acid (GPA) from Eucommia ulmoides Male flowers. Temperature-dependence properties of this IL were closely related to its N and P atoms and self-aggregation. GPA extraction was performed to obtain a maximum extraction yield (Y = 0.23 mg/g). The experimental conditions such as IL concentration, solid–liquid ratio, temperature, time, and ultrasonic power were optimized. The separation data showed that the recovery yield (R) and distribution coefficient (K) of GPA in aqueous phase were 91.95% and 3.29, respectively. The simple treated IL could be reused for 5 times for extracting, and RGPA and RIL values were decreased to 87.18% and 78.00%, respectively, indicating that this IL had a nice reusability. Molecular dynamics simulation revealed that H-bonds of [BzIm]–/H2O molecules were seriously destroyed at high temperatures, which was the major driving force for the spontaneous aggregation and liquid–liquid demixing of IL/H2O system. Further, additional H-bonds were generated of GPA and water, prompting the majority of GPA to be enriched in H2O-rich phase. Thus, [P4444][BzIm]/water system is a greenly reusable potential solvent for natural GPA extraction, and these findings are meaningful to further promote the excavation and application of analogous ILs.

An ionic liquid-assisted strategy for enhanced anticorrosion of low-energy PEO coatings on magnesium–lithium alloy

A low-energy plasma electrolytic oxidation (LePEO) technique is developed to simultaneously improve energy efficiency and anti-corrosion. Ionic liquids (1‑butyl‑3-methylimidazole tetrafluoroborate (BmimBF4)) as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid (ILs) during the LePEO process for LA91 magnesium–lithium (Mg–Li) alloy. Results show that the ionic liquid BmimBF4 participates in the LePEO coating formation process, causing an increment in coating thickness and surface roughness. The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process (LePEO-IL). After adding BmimBF4, corrosion current density decreases from 1.159 × 10−4 A·cm−2 to 8.143 × 10−6 A·cm−2. The impedance modulus increases to 1.048 × 104 Ω·cm−2 and neutral salt spray remains intact for 24 h. The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid. The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.

Impingement and breakup characteristics of free opposed impinging jets with unequal nozzle diameter

The free opposed impinging jets with unequal nozzle diameter is developed to improve mixing efficiency at unequal flowrates for liquid–liquid reactions. The liquid sheet breakup characteristics and droplet behavior are investigated using particle image velocimetry. Water, 40w% glycerol-water (40G), and 50% glycerol-water (50G) under different jet velocities and nozzle diameters are studied for comparison, the correlation equations are obtained and the errors are analyzed. When the jet velocity increases, the liquid sheet breakup mode exhibited a closed-rim mode, open-rim mode, rimless mode, wave or ligament mode, and fully developed mode for water and 40G under a nozzle diameter of 1.5–2 mm, and the first four modes were observed with the high viscosity liquid (50G) or under a large nozzle diameter (2–3 mm). As the jet velocity increases, the dimensionless breakup length increases sharply at the closed-rim and open-rim modes, and then decreases at the rimless mode. The sheet thickness, Sauter mean diameter, average droplet diameter, and droplet velocity decrease, and the droplet size becomes more uniform with increasing jet velocity. However, the opposite variation trend is observed with increasing viscosity and nozzle diameter, and the effect is more significant at u < 4.25 m/s. The droplet average diameter increases at u = 2.12 m/s and 3.18 m/s and decreases at u ≥ 4.25 m/s downwards along y-axis due to the coalescence and secondary breakup of droplets. The droplet velocity becomes lower as droplets move downwards along y-axis from −40 mm to −50 mm due to the dissipation of momentum. The results reveal that the increase of viscosity and nozzle diameter has a negative effect on liquid sheet and droplet behavior at low jet velocities. The rimless mode is the key mode affecting the transition of the sheet breakup mechanism, and after this mode, the negative effects of viscosity and nozzle diameter weaken due to the high momentum, which promotes the breakup of the liquid sheet and droplets. It will provide theoretical support for the mixing mechanism with unequal flowrates, and is helpful to expand the application of free opposed impinging jets.

A New Insight into the Flow and Pressure Behavior of a Stopper Rod Flow Control System

A previously unnoticed anomaly is recently identified in a stopper rod flow control system for the continuous casting of steel by comparing full‐scale water model experiments with plant data. Despite extensive research previously done on the continuous casting fluid flow phenomena, this anomaly and its background physics are not well understood by researchers. Computational fluid dynamics (CFD) modeling of the molten steel flow in the stopper rod system is performed with predictions matching closely with water model data but deviating from plant measurements. It is thus suggested by this comparison that certain aspects of the liquid steel flow and pressure behavior in the stopper rod system cannot be effectively described by traditional modeling techniques due to their embedded limitations. Through water modeling, CFD simulations, plant measurements, and theoretical analysis, the current study for the first time presents a thorough discussion of this observed anomaly, which brings new insights into understanding the complex fluid flow behavior and pressure distributions inside the stopper rod control system during the continuous casting process.

Understanding the breakup behaviors of liquid jet in gas atomization for powder production

Gas atomization (GA) is the main method to produce metal powders for additive manufacturing (AM) because of its low cost and high efficiency. However, the liquid breakup behaviors in high-speed gas flow during GA remains unclear, especially the primary breakup in the near field and the secondary breakup in the far field. Great difficulty exists in in-situ observation of the interactions between high-speed gas and high-temperature molten metal because of the limitations of the enclosed environment. Here, we built a new GA simulation system with a close-coupled atomizer utilizing liquids with low melting temperature, such as water, glycerin, etc. We use a high-speed camera to capture the evolution of liquid behaviors at various parameters. We first reveal that four primary breakup modes and four secondary breakup modes exist in the GA process, and these breakup modes significantly influence the particle size distribution (PSD) and the defects of the powder. Besides, the breakup modes are clarified by the dimensionless analysis. This manuscript provides an effective experimental platform to understand the breakup behaviors of the liquid jet in GA and suggests the optimal breakup mode for powder production.

GeTe ultrathin film based phase-change memory with extreme thermal stability, fast SET speed, and low RESET power energy

We designed the phase-change memory (PCM) cell based on ultrathin GeTe film (∼10 nm) and homemade nanoscale electrode filling craft to improve data retention ability and reduce programming energy, respectively. It was found that the temperature for ten years’ data retention of this ultrathin GeTe film is 160 ± 32.8 °C, which is much higher than that of conventional Ge2Sb2Te5 (GST, 83 ± 20.6 °C) film. Benefit to the nature of fragile-to-strong crossover behavior in GeTe supercooled liquids that was confined in a two-dimension structure, a fast SET speed of 6 ns is also detected in this ultrathin GeTe PCM. Moreover, the RESET power consumption of this ultrathin GeTe PCM is measured as 1.8 ± 0.5 nJ, and it is much lower than that of GST PCM (16.5 ± 1.5 nJ), which is attributed to the nanoscale electrode of the devices. The above-mentioned improvements enable the application of ultrathin GeTe PCM in neuromorphic computing.

Liquid crystalline behaviour of new dimers containing coumarin and biphenyl moieties and enhancement of their thermal conductivity: liquid crystal-nanoparticles

ABSTRACT To develop advanced heat transfer composites, new sets of unsymmetrical calamitic molecules with a coumarin unit at one end and a biphenyl group at the other end were synthesised. Their structural characterisation was investigated by routine techniques such as CHN analysis, and FT-IR, and 1D, and 2D NMR spectroscopic techniques. The liquid crystalline properties of these molecules were investigated by POM and DSC along with XRD techniques. All target compounds exhibited mesomorphic behaviour. The smectic C phase was seen for all the compounds. To enhance their thermal conductivities, conductive nanofillers, such as boron nitride nanosheets (BNNSs) and aluminium oxide nanoparticles Al2O3, were added to the synthesised liquid crystals. The LC-nanocomposites exhibit excellent thermal conducting performance when a combination of BNNSs and Al2O3 nanoparticles were added to the liquid crystals. The thermal conductivity of the 4i-BN35-A15 nanocomposite was 1.7 W/m K compared to 0.3 W/m K for the pure liquid crystal compound 4i.

Exploring the aggregation behaviour and antibiotic binding ability of thiazolium-based surface-active ionic liquids; Understanding transportation of poorly water-soluble drug

Despite significant advancements in drug delivery systems, researchers still face huge challenges in designing a suitable carrier for various drugs. Surface-active molecules having properties such as higher stability and non-toxicity can be used for sustained drug release. Herein, micellar aggregates of surface-active ionic liquids (SAILs) have been utilized, which exhibit a good ability to act as nanocarriers for poorly water-soluble drug molecules. Novel thiazolium-based SAILs, i.e., 3-dodecyl-5-(2-hydroxyethyl)− 4-methylthiazol-3-ium bromide [C12thia][Br] and 3-tetradecyl-5-(2-hydroxyethyl)− 4-methylthiazol-3-ium bromide [C14thia][Br] were synthesized and form self-assembled micellar nano aggregates in the aqueous phase. Their aggregation behaviour and interaction with poorly water-soluble antibiotic drug sulfamethoxazole (SMX) were monitored using conductivity, surface tension and isothermal titration calorimetric (ITC) techniques. The size distribution of formed aggregates was assessed using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Their efficiency as nanocarriers for the drug molecules was explored by UV–vis spectroscopy. The mathematical drug release models show a sustainable release behaviour of the SMX drug molecules from the micellar matrix. Antibacterial activity was investigated on gram-negative and gram-positive bacterial strains by measuring the inhibition zone. Efficient drug loading and enhancement in the antimicrobial activity of SMX using nano-micelles of synthesized SAILs have been observed, indicating the scope and efficacy of novel thiazolium-based SAILs as promising candidates for drug delivery applications.

Equivalent Dynamic of Liquid Sloshing Coupled with Mass Transfer During On-Orbit Refueling

During an on-orbit refueling mission, the liquid fuel partially filling in the tanks will slosh and produce coupled motion with the servicer-to-client transfer, which may bring dangers to the spacecraft and even lead to attitude divergence. To effectively simulate the motion and the inertia of liquid fuel in a cylindrical tank during refueling, equivalent dynamic modeling of liquid fuel sloshing coupled with mass transfer is developed in this paper. A spring–mass–damper model with time-varying elastic and damping coefficients is implemented in the axial direction to equal the motion of the liquid mass center, while a pendulum model with time-varying pendulum length is adopted in the radial direction. An equivalent liquid elliptical cylinder is developed to approximate the inertia of dispersed liquid while sloshing. A series of computational fluid dynamics simulations are carried out to observe the liquid behaviors in the fuel tanks and to verify the proposed equivalent dynamic model. Finally, three-dimensional sloshing is theoretically and numerically analyzed.

Influence of Parylene F Coatings on the Wetting Properties of Soft Polydimethylsiloxane (PDMS)

Understanding the wettability of soft surfaces is of key importance for the development of protective and repellent coatings and controlling droplet dynamics when required. There are many factors that affect the wetting and dynamic dewetting behavior of soft surfaces, such as the formation of wetting ridges, the adaptive behavior of the surface caused by the interaction of the fluid with the surface, or the presence of free oligomers that are washed out of the soft surface. In this work, we report the fabrication and characterization of three soft polydimethylsiloxane (PDMS) surfaces with elastic moduli ranging from 7 kPa to 56 kPa. The dynamic dewetting behavior of liquids with different surface tensions was studied on these surfaces, and the data show soft and adaptive wetting behavior of the soft PDMS, as well as the presence of free oligomers. Thin layers of Parylene F (PF) were introduced to the surfaces and their influence on the wetting properties was studied. We show that the thin layers of PF prevent adaptive wetting by preventing the diffusion of liquids into the soft PDMS surfaces and by causing the loss of the soft wetting state. The dewetting properties of the soft PDMS are enhanced, leading to low sliding angles of ≤10° for water, ethylene glycol, and diiodomethane. Therefore, the introduction of a thin PF layer can be used to control wetting states and to increase the dewetting behavior of soft PDMS surfaces.

Oleogels as a Fat Substitute in Food: A Current Review.

Fats and oils in food give them flavor and texture while promoting satiety. Despite the recommendation to consume predominantly unsaturated lipid sources, its liquid behavior at room temperature makes many industrial applications impossible. Oleogel is a relatively new technology applied as a total or partial replacement for conventional fats directly related to cardiovascular diseases (CVD) and inflammatory processes. Some of the complications in developing oleogels for the food industry are finding structuring agents Generally Recognized as Safe (GRAS), viable economically, and that do not compromise the oleogel palatability; thus, many studies have shown the different possibilities of applications of oleogel in food products. This review presents applied oleogels in foods and recent proposals to circumvent some disadvantages, as reaching consumer demand for healthier products using an easy-to-use and low-cost material can be intriguing for the food industry.

Ultrafast measurement of laser-induced shock waves

We present measurements of laser-induced shockwave pressure rise time in liquids on a sub-nanosecond scale, using custom-designed single-mode fiber optic hydrophone. The measurements are aimed at the study of the shockwave generation process, helping to improve the effectiveness of various applications and decrease possible accidental damage from shockwaves. The developed method allows measurement of the fast shockwave rise time as close as 10 µm from an 8 µm sized laser-induced plasma shockwave source, significantly improving the spatial and temporal resolution of the pressure measurement over other types of hydrophones. The spatial and temporal limitations of the presented hydrophone measurements are investigated theoretically, with actual experimental results agreeing well with the predictions. To demonstrate the capabilities of the fast sensor, we were able to show that the shockwave rise time is linked to liquid viscosity exhibiting logarithmic dependency in the low viscosity regime (from 0.4 cSt to 50 cSt). Additionally, the shockwave rise time dependency on propagation distance close to the source in water was investigated, with shock wave rise times measured down to only 150 ps. It was found that at short propagation distances in water halving the shock wave peak pressure results in the rise time increase by approximately factor of 1.6. These results extend the understanding of shockwave behavior in low viscosity liquids.