Changes In Surface Tension Research Articles

Selenium nanoparticles stabilized with chitosan for fortifying dairy products

Relevance. One solution to the problem of selenium deficiency is the enrichment of socially important food products, in particular dairy products, with bioavailable forms of selenium. Such forms include selenium nanoparticles. The aim of the work is to develop a dairy product enriched with selenium nanoparticles stabilized with chitosan.Methods. According to dynamic light scattering spectroscopy, a sample of selenium nanoparticles stabilized with chitosan has a monomodal size distribution with an average hydrodynamic particle radius of 25 nm.Results. Quantum chemical modeling of selenium nanoparticles stabilized by chitosan has revealed that the most energetically favorable interaction is the interaction of the surface of selenium nanoparticles with the hydroxo group attached to the C3 glucosamine residue of chitosan. A study was conducted of the influence of technological parameters on the stability of selenium nanoparticles stabilized with chitosan. It was found that increasing the exposure time leads to an increase in the average hydrodynamic radius of selenium nanoparticles stabilized by chitosan. In the case of pH, an inverse relationship is observed: particles with the largest average hydrodynamic radius are found in samples with an acidic environment (pH ˂ 5). As part of a study of the influence of technological parameters on the stability of selenium nanoparticles stabilized by chitosan, it was found that selenium nanoparticles stabilized by chitosan can be used as a source of selenium for food products that have a neutral pH, but can be subjected to heat treatment at temperatures above 70 °C in for 5–15 minutes, in particular pasteurized milk. A study of pasteurized milk fortified with selenium nanoparticles stabilized by chitosan showed that there were no significant changes in titratable acidity, surface tension and pH of milk, as well as the average hydrodynamic radius of casein micelles after milk fortification. The value of antioxidant activity increases by 0.88% — from 6.50 to 7.38%.

Properties of Chemically Stabilized Methanol–HVO Blends

Approximately 25% of global carbon emissions come from food production. Renewable fuels are crucial for curbing greenhouse gas (GHG) emissions from vehicles, non-road machines, and agricultural machinery. Tractors, key to modern farming, are central to these efforts. As agriculture strives for sustainability, alternative fuels like methanol and hydrotreated vegetable oil (HVO) are arousing interest because they are renewable and offer potential for blending for use in diesel engines. Methanol and HVO have limited solubility in direct mixing, so the addition of a co-solvent is essential. This study addresses the research gap regarding the properties of HVO and methanol blends with co-solvents. It investigated the impact of three co-solvents, 1-dodecanol, 1-octanol, and methyl butyrate, on the miscibility of HVO and methanol. The experimental measurements cross-varied the co-solvent type with different blending ratios (MeOH5 and MeOH10). Investigated parameters include fuel density, kinematic viscosity, distillation properties, and surface tension. The co-solvents enabled the formation of a singular, clear, and homogeneous phase in methanol-HVO blends. The co-solvent 1-dodecanol demonstrated the highest solubilizing capacity for MeOH5 and MeOH10 blends, followed by 1-octanol. Adding co-solvents led to increased fuel density, decreased kinematic viscosity, and small changes in surface tension. These findings contribute to the optimization of methanol–HVO fuel blends for efficient and environmentally friendly use in vehicles, non-road machinery, and agricultural machinery.

Yttrium induced formation of new pores in an as-cast nickel-based single crystal superalloy

Pores are the most fatal defects in single crystal superalloys, which severely deteriorates the mechanical properties. Yttrium (Y) has been applied in commercial superalloys, but its effect on the morphology change of casting pores is not clear. This work focuses on the effect of Y on the evolution of pores formed after directional solidification in a second-generation superalloy. SEM, TEM and XRT were used to characterize the pores, and Thermo-Calc was used to calculate the surface tension change during the solidification process. Results show that, besides the formation of two types of conventional shrinkage pores during solidification, new types of pores, i.e., Type III and Type IV, due to the addition of Y element to 0.5 wt% in superalloy, were also observed. The formation of Type III pore could be ascribed to the surface tension drop in the liquid phase, which enhances the wettability at the solid/liquid interface, and promotes the mobility of liquid phase, due to the incorporation of Y element. The formation of Type IV pore is due to the simultaneous formation and growth of M23C6 and Ni3Al in the Ni5Y phase, triggering the formation of closed zone with a small but irregular shape at the multi-phase interface.

INVESTIGATION OF SURFACE PROPERTIES OF MODIFIED BITUMEN COMPOSITIONS

One of the main reasons for premature destruction of road surfaces is the poor quality of road bitumen. An effective way to improve the quality of a bitumen binder is to modify it with polymer or surface-active additives. The goal is to determine the effect of the concentration of modifiers on surface tension in binary "bitumen-surfactant", "bitumen-polymer" and triple "bitumen-surfactant-polymer" systems. The methodology of the work included measuring the surface tension of modified bitumen systems depending on the quantitative content of additives in bitumen. Results and discussion: As follows from the analysis of the data obtained, in bitumen systems with a limited concentration of polymer AG-4I (C≤1 g/dm3), the effect of reducing surface energy at the interface with air is achieved by concentrating surfactants in the surface layer, which are part of the structure of the bitumen itself. The extreme nature of the change in surface tension was also recorded in AC-2 bitumen compositions. Conclusion: In the "bitumen-AG-4I-AS-2" triple systems, the change in the specific surface energy at the "liquid-gas" interface is not an additive value, taking into account the separate contribution of AG-4I and AS-2. The concentration threshold of additives to achieve a minimum surface tension varies in comparison with binary compositions. With the combined administration of AG-4I (C=1g/dm3) and AC-2 (C=1g/dm3), the surface tension decreased by 9.30 mN/m compared with unmodified bitumen.

Experimental investigation of mechanical and physical properties of glass fiber reinforced concretes produced with different magnetized waters

Magnetized water may act as a thickener in cementitious mixtures due to its slippery effect. Therefore, it can be beneficial for the mixture to settle easily and to improve its strength. This study investigated the effects of magnetized water passing through pipes with magnetic field intensity (MFI) 8 and 10 on glass fiber reinforced concrete (GFRC). Three different mixtures, the GFRC mixture produced with regular tap water, were obtained, and the properties of the produced GFRC samples, such as 7, 14, and 28 days H-Leeb hardness, density, Ultrasonic pulse velocity (UPV), flexural strength, compressive strength, and fracture mechanics were investigated. In addition, SEM, EDS, FTIR, and TGA analyses were carried out to investigate the change in surface tension in the internal structures of GFRCs produced with magnetized water. Overall, the results were promising. Results showed a proportional H-Leep hardness increase with curing time and density variations. Magnetized water reduced air voids, enhancing sound transmission speeds. Flexural and compressive strength improved with magnetic water. The study suggests significant contributions to energy savings and reduced production costs, highlighting the efficient use of energy resources.

The role of [formula omitted] on controlling the pure vaterite transformations

Vaterite calcium carbonate (CaCO3) possesses unique advantages compared to calcite; however, some critical issues need to be addressed, such as vaterite stability. Numerous studies have indicated that NH4+ can promote vaterite formation and prevent its transformation. However, as vaterite is an instantaneous microscopic process that is easy to transform, directly revealing the role of NH4+ in stabilizing vaterite remains challenging in experiments. This research aims to reveal the role of NH4+ in stabilizing vaterite and retarding phase transformations. Vaterite stabilization was investigated at different NH4+ concentrations and characterized by XRD and SEM. The reaction system’s pH, electrical conductivity, and surface tension changes were analyzed in the presence of NH4+. Computational and experimental studies were utilized to determine the role of NH4+ in the stabilization of vaterite. Results revealed that NH4+ can significantly increase the existence time of vaterite in the water solution. The density functional theory (DFT) indicated that the adsorption energy of NH4+ and vaterite (110), (112), and (114) is obviously higher than that of H2O molecules. The molecular dynamics (MD) simulation research shows that NH4+ can replace water molecules on the crystalline surface of vaterite and mainly interact with carbonate ions on the surface of vaterite. The mechanism analysis shows that the inhibitory effect of NH4+ on the phase transformation of vaterite is primarily caused by preventing the dissolution process. This study systematically explains the role of NH4+ in the stability of vaterite and further reveals that NH4+ can not only promote the formation of vaterite but also play a decisive role in inhibiting its phase transition.

Interfacial Behavior of Biodegradable Poly(lactic-co-glycolic acid)-Pluronic F127 Nanoparticles and Its Impact on Pickering Emulsion Stability.

Biodegradable nanoparticle-based emulsions exhibit immense potential in various applications, particularly in the pharmaceutical, cosmetic, and food industries. This study delves into the intricate interfacial behavior of Pluronic F127 modified poly(lactic-co-glycolic acid) (PLGA-F127) nanoparticles, a crucial determinant of their ability to stabilize Pickering emulsions. Employing a combination of Langmuir balance, surface tension, and diffusion coefficient measurements, we investigate the interfacial dynamics of PLGA-F127 nanoparticles under varying temperature and ionic strength conditions. Theoretical calculations are employed to elucidate the underlying mechanisms governing these phenomena. Our findings reveal a profound influence of temperature-dependent Pluronic layer behavior and electrostatic and steric interactions on the interfacial dynamics. Nonlinear changes in surface tension are observed, reflecting the interplay of these factors. Particle aggregation is found to be prevalent at elevated temperatures and ionic strengths, compromising the stability and emulsification efficiency of the formed emulsions. This work provides insights into the rational design of stable and efficient biodegradable nanoparticle-based Pickering emulsions, broadening their potential applications in various fields.

Impact of solvent temperature on graphite shear exfoliation efficiency

Liquid phase exfoliation (LPE) of graphite is a promising pathway for graphene flakes (GF) due to its scalability and cost-effectiveness. However, the method has significant limits at the industrial scale, such as low yield of GF and long processing times. In this study, we investigate the effect of organic solvents such as N-methyl-2-pyrrolidone (NMP) and methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (PolarClean) temperature on shear-induced exfoliation. The GF concentration was successfully obtained 0.62 mg/ml in NMP and 0.68 mg/ml in PolarClean within just 2 h at 263 K, without surfactants or any additional additives. These results revealed the improved exfoliation efficiency due to changes in solvent polarity, surface tension, and dispersion stability with increased viscosity. In addition, we investigate the optimization conditions required for liter-scale shear-induced exfoliation of graphite in PolarClean. As-prepared GF has significant potential as an effective nanofiller for enhancing the mechanical strength of commercial polymers. This study not only advances the understanding of the LPE mechanisms but also paves the way for the industrial application of this method in the green synthesis of graphene-based nanocomposites.

A Study on the Dilational Modulus Measurement of Polyacrylic Acid Films at Air-Water Interface by Pendant Bubble Tensiometry.

The dilational modulus (E) of polymer films has been commonly measured using the oscillating ring/bubble/drop methods with an external force, and often without specifying the state of the adsorbed film. This study explores an approach where E was determined from the relaxations of surface tension (ST) and surface area (SA) of natural perturbations, in which ST and SA were monitored using a pendant bubble tensiometer. The E of the adsorbed film of PAA (polyacrylic acid) was evaluated for aqueous solutions at CPAA = 5 × 10-4 g/cm3, [MW = 5, 25, and 250 (kDa)]. The E (=dγ/dlnA) was estimated from the surface dilational rate (dlnA/dt) and the rate of ST change (dγ/dt) of the bubble surface from the natural perturbation caused by minute variations in ambient temperature. The data revealed that (i) a considerable time is required to reach the equilibrium-ST (γeq) and to attain the saturated dilational modulus (Esat) of the adsorbed PAA film, (ii) both γeq and Esat of PAA solutions increase with MW of PAA, (iii) a lower MW solution requires a longer time to reach its γeq and Esat, and (iv) this approach is workable for evaluating the E of adsorbed polymer films.

Beverage Deterioration Monitoring Based on Surface Tension Dynamics and Absorption Spectrum Analysis

Biochemical information sensing has always been one of the challenges in ubiquitous sensing research for mobile computing. Microorganisms will cause undetectable deterioration in drink production, such as wine and beverage, and microbial contamination is highly susceptible during storage like some liquors can be bottled for sometimes over ten years. Microbial culture methods are common for quality monitoring but unsuitable for real-time beverage quality monitoring. As far as we know, we are the first to use ubiquitous sensing for real-time microbial contamination detection. We designed a lightweight monitoring system called Microbe-Radar, which uses light signals to monitor real-time beverage quality. Microbe-Radar uses eight LEDs and a photodiode to detect fine-grained surface tension and absorption spectrum changes caused by microbial metabolites and growth during deterioration. Characteristic offset degree measurement and absorption spectrum dimension expansion are two critical technologies. Moreover, we implemented countermeasures against ambient light noise and sloshing interference. Microbe-Radar's surface tension and absorption spectrum measurement errors are only 0.89 mN/m and 2.4%, respectively, making identifying the contamination duration, microorganism content, and microorganism composition worthwhile. Experiments showed Microbe-Radar could determine potential issues with liquor quality when the liquid becomes health-threatening or even just contaminated, with an accuracy of 97.5%. Microbe-Radar can also be extended to beverage deterioration warning, with deterioration prediction accuracy of more than 90.6% for five beverages (milk, apple juice, etc.).

Importance of the Electrostatic Correlations in Surface Tension of Hydrated Reline Deep Eutectic Solvent from Combined Experiments and Molecular Dynamics Simulations.

In this study, the surface tension and the structure of hydrated reline are investigated by using diverse methods. Initially, the surface tension displays a nonlinear pattern as water content increases, decreasing until reaching 45 wt %, then gradually matching that of pure water. This fluctuation is associated with strong electrostatic correlations present in pure reline, which decrease as more water is added. Changes in surface tension reflect a shift from charge layering in pure reline to an increased interfacial hydrogen bonding as the water content rises. This shift causes the segregation of urea molecules into the bulk phase and a gradual anchoring of water molecules to the air-reline interface. An interesting observation is the antisurfactant effect, where heightened interfacial anchoring results in an unexpected increase in real contribution of surface tension. This, along with weakened electrostatic correlations beyond 45 wt % due to reinforced interfacial hydrogen bonding, contributes to the complex behavior of surface tension observed in this study.

Strong impact of exposure to water/solvent mixtures on permeance of nanofiltration membranes

Water/solvent mixtures released from industrial processes, especially in pharma and fine chemical synthesis or in advanced oil production, are an environmental concern, necessitating the development of efficient remediation and recycling techniques. Solvent-tolerant nanofiltration (STNF), situated between aqueous nanofiltration (NF) and solvent-resistant nanofiltration (SRNF), offers a promising solution. This study investigates the potential of using aqueous NF- and SRNF-membranes to treat water/solvent mixtures. Commercial membranes (NF270, DuraMem® 300, DuraMem® 200) and a lab-synthesized polyvinylidene fluoride (XL-PVDF NF) membrane were used to treat dimethyl sulfoxide (DMSO), acetonitrile (ACN), Isopropyl alcohol (IPA), or dimethylformamide (DMF) mixtures with water. The addition of 10% DMSO, ACN, IPA, or DMF to water significantly reduced the permeance of these NF-membranes, and an increase in temperature failed to restore the initial permeance. Changes in both viscosity and surface tension of the water/solvent solutions strongly influence the permeance of the NF-membranes. Flory-Huggins and Zimm-Lundberg theories offered an explanation for the phenomenon where solvent clusters form within the dense polymer matrix of NF-membranes upon exposure to water/solvent mixtures, resulting in decreased water permeabilities. NMR analysis identified of the presence of small amounts of solvents in the STNF-membranes, even still after prolonged exposure to pure water permeation. The results emphasize the current shortcomings of aqueous and solvent-resistant membrane chemistries in handling water/solvent mixtures. Minor solvent additions significantly modify NF membrane permeance, emphasizing the need for innovative material design, especially given the variable solvent content in industrial applications.

Biodegradation capabilities of filamentous fungi in high-concentration heavy crude oil environments.

In this comprehensive study, we delved into the capabilities of five fungal strains: Aspergillus flavus, Aspergillus niger, Penicillium chrysogenum, Penicillium glabrum, and Penicillium rubens (the latter isolated from heavy crude oil [HCO]) in metabolizing HCO as a carbon source. Employing a meticulously designed experimental approach, conducted at room temperature (25°C), we systematically explored various culture media and incubation periods. The results unveiled the exceptional resilience of all these fungi to HCO, with A. flavus standing out as the top performer. Notably, A. flavus exhibited robust growth, achieving a remarkable 59.1% expansion across the medium's surface, accompanied by distinctive macroscopic traits, including a cottony appearance and vibrant coloration. In an effort to further scrutinize its biotransformation prowess, we conducted experiments in a liquid medium, quantifying CO2 production through gas chromatography, which reached its zenith at day30, signifying substantial bioconversion with a 38% increase in CO2 production. Additionally, we monitored changes in surface tension using the Du Noüy ring method, revealing a reduction in aqueous phase tension from 72.3 to 47mN/m. This compelling evidence confirms that A. flavus adeptly metabolizes HCO to fuel its growth, while concurrently generating valuable biosurfactants. These findings underscore the immense biotechnological potential of A. flavus in addressing challenges related to HCO, thereby offering promising prospects for bioremediation and crude oil bioupgrading endeavors.

Photoresponsive arylazopyrazole surfactant/PDADMAC mixtures: reversible control of bulk and interfacial properties.

In many applications of polyelectrolyte/surfactant (P/S) mixtures, it is difficult to fine-tune them after mixing the components without changing the sample composition, e.g. pH or the ionic strength. Here we report on a new approach where we use photoswitchable surfactants to enable drastic changes in both the bulk and interfacial properties. Poly(diallyldimethylammonium chloride) (PDADMAC) mixtures with three alkyl-arylazopyrazole butyl sulfonates (CnAAP) with -H, -butyl and -octyl tails are applied and E/Z photoisomerization of the surfactants is used to cause substantially different hydrophobic interactions between the surfactants and PDADMAC. These remotely controlled changes affect significantly the P/S binding and allows for tuning both the bulk and interfacial properties of PDADMAC/CnAAP mixtures through light irradiation. For that, we have fixed the surfactant concentrations at values where they exhibit pronounced surface tension changes upon E/Z photoisomerization with 365 nm UV light (Z) and 520 nm green (E) light and have varied the PDADMAC concentration. The electrophoretic mobility can be largely tuned by photoisomerisation of CnAAP surfactants and P/S aggregates, which can even exhibit a charge reversal from negative to positive values or vice versa. In addition, low colloidal stability at equimolar concentrations of PDADMAC with CnAAP surfactants in the E configuration lead to the formation of large aggregates in the bulk which can be broken up by irradiation with UV light when the surfactant's alkyl chain is short enough (C0AAP). Vibrational sum-frequency generation (SFG) spectroscopy reveals changes at the interface similar to the bulk, where the charging state at air-water interfaces can be modified with light irradiation. Using SFG spectroscopy, we interrogated the O-H stretching modes of interfacial H2O and provide qualitative information on surface charging that is complemented by neutron reflectometry, from which we resolved the surface excesses of PDADMAC and CnAAP at the air-water interface, independently.

Operando Identification of Temperature-Dependent Pore-Scale Gas Saturations in PEM Water Electrolyzers

Polymer electrolyte membrane (PEM) water electrolysis is a promising solution for the chemical storage of intermittent renewable energy in the form of clean hydrogen (1). For the widespread adoption of this technology, the efficiency of PEM electrolyzers must be improved through informed material design and tailored operating conditions to compete with incumbent carbon-emitting technologies (2). A main source of inefficiency is related to mass transport losses, where oxygen gas, a by-product of the anode reaction, accumulates in the anode porous transport layer (PTL) and hinders reactant liquid water delivery to reaction sites (3). Although extensive studies have explored this two-phase flow phenomenon, the consideration of operating temperature on gas accumulation in the PTL adds further complexity. A duality in temperature effects has been reported in the literature where increasing the operating temperature may encourage gas coverage which obstructs liquid water transport, but it may also enhance liquid water delivery due to favorable fluid property changes in viscosity and surface tension (4). Efforts have been made previously to reconcile these competing observations using 2D visualization methods (5), however a closer investigation using 3D visualization techniques will provide valuable pore-scale insights in the comprehensive understanding of the impact of operating temperature on gas transport in the PTL, and subsequently mass transport losses in the PEM electrolyzer.In this work, we employed operando X-ray computed tomography (CT) to visualize three-dimensional (3D) pore-scale gas saturations in the PTL at various industrially relevant operating conditions. Specifically, a custom in-house electrolyzer was imaged with synchrotron CT at five different temperatures (40°C, 50°C, 60°C, 70°C, 80°C) and current densities ranging from 0.5 A/cm² to 4.0 A/cm² with 0.5 A/cm² incremental steps. Electrochemical impedance spectroscopy and Tafel measurements were also acquired to characterize the relationship between gas distributions and corresponding mass transport overpotentials. Considering X-ray transparency, a model PTL made of carbon fibers was used to achieve sufficient contrast to quantify water and gas in the obtained images. Using precise volume registration and subtraction methods, pore-scale gas distributions in the PTL were quantified to reveal changes in bubble accumulation and coverage area at different operating temperatures and over operation time. The novel insights from this work will aid in our understanding of the complex relationship between operating temperature and multiphase flow phenomena in the PTL, which is vital for tailoring operating conditions of PEM electrolyzers to curtail the costs of green hydrogen production.

Experimental study on the dynamic wetting of silica nanofluids

Nanofluids are recently discovered nanomaterials with improved thermophysical properties that can enhance the efficiency and reliability of heat transfer systems. Their relevant properties for describing heat transfer, thin film flows, droplet impingements, or microfluidics are surface tension and wettability. A thorough investigation on this topic of research is crucial to understand the root cause of the factors affecting the degree of wetting of nanofluids on solid surfaces. In the present work, silica (SiO2) nanofluids with different mass fractions and types of surfactants based on deionized water were prepared using a simple and cheap two-step method. The effect of surface tension changes on the lateral friction force of the nanofluid was studied using a solid–liquid interface lateral friction force detection system. According to the findings, an increase in the mass fraction of silica nanoparticles led to the larger surface tension of the nanofluid, resulting in a linear decrease in the lateral friction of the latter on the hydrophobic surface of PDMS. The use of ionic surfactants as dispersants caused a dramatic decrease in surface tension and static angle of SiO2 nanofluid (by 20% and 30% after adding SDS and by 40% and 50% after adding CTAB, respectively). This exerted a noticeable impact on the lateral friction force of the fluid. On the contrary, polymeric surfactants (NaPSS) had a small effect on the lateral friction of SiO2 nanofluid. Meanwhile, the lateral friction after stable motion differed from the maximum static friction to a small extent.

Surfactants on troubled waters

‘Storm oil’ – nearly water-insoluble oil poured into the ocean and acting as a surfactant – has been used since ancient times to smooth the waves on the ocean. It was first scientifically described by Benjamin Franklin (Phil. Trans. R. Soc. Lond., vol. 64, 1774, pp. 445–460). In a recent paper, by combining highly controlled experiments in a wave tank and direct numerical simulations, Erinin et al. (J. Fluid Mech., vol. 972, 2023, R5) have now beautifully revealed the strong effect of soluble surfactants on the dynamics of plunging breakers. Remarkably, it is not the change in surface tension which mainly matters, but the surface tension gradient which emerges through compression and dilation of the plunging breaker surface.

Hypothesis and theory: Do trees “release the tension” in rainwater? Surface tension reduction in throughfall and stemflow from urban trees

Knowledge of the processes and impacts associated with the canopy’s partitioning of rainfall into stemflow (water that drains to the base of tree stems) and throughfall (water that drips through gaps and from canopy surfaces) has expanded in recent years. However, the effect of canopy interactions on the fundamental physical properties of rainwater as it travels through the canopy to the soil, particularly surface tension, remains understudied. To discuss specific hypotheses within this context and their relevance to ecohydrological theory, the surface tension of rainwater samples was examined directly. Over a period of 9 months, open rainwater, throughfall and stemflow samples were collected during 20 storms from 12 study trees located in Secrest Arboretum (about 2.5 km outside Wooster, Ohio). Study trees were selected to highlight a range of canopy characteristics, with each tree being from a unique deciduous species. Surface tension was measured using pendant drop goniometry, and measurements were analyzed for variation across study trees and correlation with event air temperature and rain intensity. In general, surface tension was reduced in throughfall and stemflow compared to measurements made for event rainwater, with median surface tension changes of −0.446 mN m−1 and −0.595 mN m−1 for throughfall and stemflow, respectively. The extent of this reduction varied among study trees (with changes as great as −6.5 to −5.5 mN m−1), and storm event characteristics were directly and indirectly correlated with surface tension changes in select cases. Hypothetically, a number of mechanisms may account for the observed reduction (and variation in this reduction) in surface tension, including differences in tree surface properties, canopy microenvironments, and microbiomes, and each warrant further research. Testing these hypotheses may advance broader ecohydrological theory as surface tension changes will influence wetting, absorption, and solute exchange processes within the canopy which, in turn, may affect related surface processes.

Enzymatic degradation pattern of polysorbate 20 impacts interfacial properties of monoclonal antibody formulations

Polysorbate 20 (PS20) is widely used to maintain protein stability in biopharmaceutical formulations. However, PS20 is susceptible to hydrolytic degradation catalyzed by trace amounts of residual host cell proteins present in monoclonal antibody (mAb) formulations. The resulting loss of intact surfactant and the presence of PS20 degradation products, such as free fatty acids (FFAs), may impair protein stability. In this study, two hydrolytically-active immobilized lipases, which primarily targeted either monoester or higher-order ester species in PS20, were used to generate partially-degraded PS20. The impact of PS20 degradation pattern on critical micelle concentration (CMC), surface tension, interfacial rheology parameters and agitation protection was assessed. CMC was slightly increased upon monoester degradation, but significantly increased upon higher-order ester degradation. The PS20 degradation pattern also significantly impacted the dynamic surface tension of a mAb formulation, whereas changes in the equilibrium surface tension were mainly caused by the adsorption of FFAs onto the air–water interface. In an agitation protection study, monoester degradation resulted in the formation of soluble mAb aggregates and proteinaceous particles, suggesting that preferential degradation of PS20 monoester species can significantly impair mAb stability. Additional mAbs should be tested in the future to assess the impact of the protein format.

Surface-tension change of graphene-based water nanofluid and its effects on heat-transfer process

Nanofluids with high thermal conductivities are gaining attention for heat-exchange applications, particularly in boiling processes. Nanofluid heat-transfer efficiency is significantly influenced by the surface tension (ST) and wettability patterns of the nanofluid. This study investigated graphene-based water nanofluids prepared from three different viscoelastic polymer solutions. The effects of the dispersant, graphene concentration, and temperature on the ST were investigated, and the wetting behavior of nanofluids on stainless steel and polypropylene random surfaces was determined. The results indicated that the ST of the nanofluids exhibited a negative correlation with the dispersant concentration and temperature. Additionally, the inclusion of graphene reduced the ST in xanthan-gum systems but increased it in sodium carboxymethyl cellulose and polyethylene-oxide systems. Overall, the nanofluids exhibited a lower ST than water. The decrease in the nanofluid ST is ascribed to the development of a rigid network resulting from the co-adsorption of graphene nanoparticles and the dispersant at the gas–liquid interface. Furthermore, graphene has been demonstrated to enhance the wettability of the base fluids of various materials. A decrease in ST led to increased frictional resistance; however, this was counteracted by an increase in the contact angle, resulting in an overall reduction in frictional resistance. Moreover, reducing the ST can improve the fluid boiling heat transfer. Therefore, these nanofluids exhibited the dual effect of reduced flow resistance and enhanced heat-transfer efficiency. This study offers valuable insights into the behavior of nanofluids and their potential applications in areas such as energy storage and spacecraft thermal management.