Contact Angle Measurement Method Research Articles

Investigating the Effects of Lubricant Infusion Methods on Polymer SLIPS.

Slippery lubricant infused porous surfaces (SLIPSs) are promising bioinspired surfaces with self-healing and droplet wetting properties, among many others, that are desirable due to their range of applications. Recently, there have been many developments in the SLIPS field regarding the creation of textured surfaces and lubricant selection. However, there is a lack of knowledge regarding the method of lubricant infusion. In this study, we aim to fill this void by investigating different infusion methods that impose external forces on the lubricant. We developed our SLIPS by hot embossing nanostructures onto polypropylene by using molds that were laser micromachined. These textured surfaces were then infused with silicone oil using three different infusion methods: ultrasonication, vacuum, and hydrostatic pressure. We analyzed the wettability and slipperiness of the SLIPS by evaluating the critical tilt angle and comparing the sliding velocities of water droplets on each sample at a tilt angle of 20°. Additionally, the durability of the SLIPS was tested by dropping 50 successive water drops onto the samples and evaluating the droplet-surface interactions throughout. The sonicated infusion method yielded SLIPS that performed the best with a contact angle hysteresis of 13°, a critical tilt angle of 18.3°, a sliding velocity of 1.66 mm/s, and the least accumulation of droplets over time with use. These values are greatly improved when compared to the control sample where lubricant was simply dripped on, which resulted in a contact angle hysteresis of 20°, a critical tilt angle of 26.3°, and a sliding velocity of 0.23 mm/s. The sonicated and drip infusion methods were also compared with different materials (stainless steel) and different textures (microstructures). It was found that the improvement in slipperiness using the sonicated infusion method is prominent for nanoscale textures on both stainless steel and polypropylene. In this study, we discuss the challenges with oil depletion in SLIPS (cloaking and wetting ridges) and with the selection of contact angle measurement methods. While further investigation as to why certain applied forces during infusion yield better SLIPS is warranted, these forces greatly affect the outcome. This work suggests that researchers should consider using sonication or other methods of lubricant infusion that apply external forces as infusion techniques to yield better SLIPS on the nanoscale.

The effect of methylene blue on stearic acid-aged quartz/CO2/brine wettability: Implications for CO2 geo-storage

Carbon dioxide sequestration in geological formations has been proposed as a promising solution to reach net zero carbon emissions but the success of underground CO2 storage in sandstone formations depends on the brine/CO2 wettability of sandstone. Research evidence showed that natural geological formation is hydrophobic even in the presence of minute concentration of inherent organic acids. This study investigates the effect of methylene blue (MB) on CO2 wettability of organic-acid contaminated quartz through the tilted plate contact angle measurement method. Pure quartz substrates were aged in a stearic acid/n-decane solution for one week and subsequently modified with different concentrations of MB (ranging from 10 to 100 mg/L) at a temperature of 60 °C. Advancing (θa) and receding (θr) contact angles were measured under varying conditions of temperature (25 °C and 50 °C), pressure (ranging from 10 to 20 MPa), and salinity (0–0.3 M). The experimental results indicate that pure quartz, when aged in a stearic acid solution, becomes CO2-wet at all temperature, pressure, and salinity conditions. However, at any physio-thermal condition, the wettability of the quartz surfaces was reversed when treated with different concentrations of MB, transitioning to a water-wet state. The findings of this research demonstrate the potential of MB to modify the wetting behaviour of quartz surfaces and enhance CO2 residual trapping in sandstone formations.

TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membrane: Improvement in flux and anti-fouling properties

Based on the previous study, the properties, separation efficiencies, and anti-fouling performances of TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membrane made via non-solvent-induced phase separation were investigated. SEM, contact angle measurement, ATR-FTIR, and other methods were used to characterize the membranes, and then the pure water flux (PWF) and dye rejection were measured. The TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membranes were prepared by stepwise solution blending method. Compared to the pristine PEEKWC/PEI cross-linked ultrafiltration membrane, the anti-fouling and pure water flux performances were enhanced as the addition of TiO2 nanoparticles. The pure water flux of TiO2 nanoparticle embedded membranes was significantly increased and could even reach 3368.2 LMH at 5 bar much greater than that of the pristine PEEKWC/PEI ultrafiltration membrane (1423.8 LMH), remaining a retention rate for BBR higher than 98.5%. And the TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membranes exhibited a certain degree of increase of FRR (higher than 80%) after UV illumination. After a series of characterisation, the dye wastewater treatment property of membranes was assessed through filtration of Coomassie brilliant blue and Congo red solutions and researches were conducted on the anti-fouling capabilities of membranes. The TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membranes exhibited self-cleaning efficiency with lower irreversible fouling ratio. The pure water flux recovery ratio following dye fouling was higher after being exposed to UV irradiation, which could be attributed to the TiO2 nanoparticles' photocatalytic destruction of organic pollutants.

Harvesting of Water from Atmospheric Air using Electrospun PVP- PVC Nanofibers with TEC Atmospheric Generator

Water scarcity is a worldwide problem. The need for freshwater is increasing as a result of many factors such as population growth, industrial development and climate change. Water treatment methods such as desalination process produce a good amount of water. However, it is costly, require large space and high amounts of energy especially in remote areas. So, alternative water resources, such as air water harvesting must be considered as a possible water source especially for hot and humid regions. In this paper, a prototype of air water generator was designed, built, and tested. The operation of the prototype is based on harvesting water from air using Peltier effect also known as thermoelectric cooling device [TEC]. The system was conducted under different conditions: ambient temperature [28 &29] °C, relative humidity [47, 59, 68, 75, 85, and 95] %. Two collecting surfaces were used, aluminium foil, and electrospun polyvinyl chloride [PVC] combined with polyvinylpyrrolidone [PVP] nanofiber. Based on the results obtained, it was found that using PVC-PVP nanofiber increased the amount of harvested water. At temperature 29°C and RH 95%, the prototype produced an average water of 104.94 mg/cm2.h using nanofiber, and only 89.44mg/cm2.h using aluminium foil surface. The nanofiber is hydrophobic, with water contact angle of 130.25°. The harvested water was tested for water quality. It is observed that most results comply with Jordanian Drinking Water Standards and World Health Organization. The chemical structures of the nanofibers was characterized by Fourier transform infrared [FTIR], Scanning electron microscopy [SEM] and water contact angle measurement method to determine the morphology and surface hydrophobicity of the nanofiber.

The anti SARS-CoV-2 activity of nanofibrous filter materials activated with metal clusters.

Nanofibrous filter materials were prepared by electrospinning a solution of 28wt% poly(vinylidene fluoride) in N,N-dimethylacetamide with and without the addition of 2wt% AgNO3, Cu(NO3)2·2.5H2O or ZnCl2. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectroscopy, thermogravimetric analysis, contact angle measurement, nitrogen sorption, and mercury intrusion porosimetry methods were used for the characterization of physical structure as well as the chemical composition of the electrospun materials. Particle filtration efficiency and antiviral activity against the SARS-CoV-2 alpha variant were tested in order to estimate the suitability of the prepared electrospun filter materials for application as indoor air filtration systems with virucidal properties. All filter materials prepared with salts demonstrated very high particle filtration efficiency (≥98.0%). The best antiviral activity was demonstrated by a material containing Cu(NO3)2·2.5H2O in the spinning solution, which displayed the decrease in the number of infectious virions by three orders of magnitude after a contact time of 12h. Materials with the addition of AgNO3 and ZnCl2 decreased the number of infectious virions after the same contact time by only ∼8 and ∼11 times, respectively.

Experimental basis for determining contact angle in the ideal model of unsaturated soils

In an ideal unsaturated soil model, the contact angle (CA) is often determined by the sessile drop method (SDM), or assumed without any test. However, both approaches can lead to errors in the model calculation results. In this study, methods that combine models of unsaturated soil with CA measurement methods is presented. The characteristics of soil CA were studied using the sessile drop method (SDM) and the direct observation method (DOB). The results demonstrated that the CA values of soils and CA variation characteristics measured with SDM were significantly different from those measured with DOB. SDM measures the CA of a surface, which is a “plane” formed by many particles, whereas DOB measures the CA between soil particles on a smaller scale. The measurement results of SDM can determine the degree of soil hydrophobicity but may cause large errors when used as a parameter of an ideal unsaturated soil model. The DOB can simulate the natural drying-wetting cycles of soils, and its measurement results are closer to the natural conditions. Using the mean CA as a model parameter is reasonable, except when the CA value is 0. The hysteresis phenomenon caused by using CA hysteresis for the soil-water characteristic curve (SWCC) is likely to overestimate the effect of CA hysteresis on soil water retention behavior.

Influence of magnetic casting on the permeability and anti‐fouling properties of a novel iron oxide/alumina/polysulfone mixed matrix membrane

AbstractNovel mixed matrix membranes (MMMs) were fabricated using Fe3O4, and Al2O3nanoparticles (NPs) were added to the polysulfone (PSf) and N‐methylpyrrolidone (NMP) solution. The nanocomposite membranes were fabricated using the NIPS (non‐solvent induced phase separation) method. In order to create preferential permeation pathways for water across the MMMs, membrane formation is accomplished with an external magnetic field. Using magnetic casting cause the targeted placement of NPs in the best location and orientation. The performance of the prepared membranes was examined in terms of pure water flux and fouling parameters. Magnetic casting considerably increased pure water flux and decreased the total resistance of the optimum mixed matrix membrane, which contains 0.2% wt. of Fe3O4NPs to 1175 L/m2h and 13.4 * 1011(m−1), respectively. This is explained by the ordering of magnetic nanoparticles on the membrane sub‐layer cast under the magnetic field of 500 mT, which changed the sub‐layer structure. Less rough membrane surface of the mixed matrix membranes offered preferable anti‐fouling properties against fouling by BSA proteins. The characterization of fabricated membranes was carried out using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive X‐ray (EDX), and water contact angle measurement methods.

Investigation of Structural and Thermal Properties of Graphene Oxide Reinforced Epoxy Nanocomposites

The nanocomposites thin film was prepared by adding exfoliated GO in epoxy-hardner solution in different weight ratio. We investigate the thermal and surface properties of epoxy-graphene oxide (GO) nanocomposites using differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle measurement method. AFM and contact angle results are supporting that graphene oxide provides the best reinforcement in epoxy. AFM is investigated the dispersion of GO and structural morphology of epoxy nanocomposites. The FTIR results show that exfoliated GO of two-dimensional (2D) shape favors the hardening process of the epoxy matrix, increasing its reaction rate by observing an epoxy stretching frequency at 907 cm−1. The GO modified with amino group of epoxy lead to the increase of crosslinking density. FTIR absorption peak in 1700–1500 cm−1 regions is due to amino group. This attributes the significant increase of glass transition temperature of epoxy/GO nanocomposites . The contact angle and surface roughness increases with increase in concentration of GO in epoxy shows roughness induced hydrophobic surface. The solid surface energy was calculated by contact angle favors the good dispersion of GO in epoxy matrix.

The effect of the electrospinning setup on the surface energy of polycaprolactone nanofibre layers

The study addresses changes in the surface energy of polycaprolactone nanofibre layers due to the different spinning electrodes. The value of surface energy and the associated wettability is an important aspect of polymeric biomaterials that influence the quality of interaction with biological material. The study involved the production of nanofibre layers by means of both needle and needleless electrospinning. The surface energy of the produced layers was determined via the contact angle measurement method. The experiment revealed that the spinning electrode exerts a significant effect on the resulting surface energy and, thus, on the wetting of the nanofibre layers. It was discovered during the measurement process, that the fibre layers produced via the needle electrospinning method evinced a low surface energy and are non-wettable/hydrophobic. In contrast, needleless electrospinning fibre layers evince a high surface energy and are wettable/hydrophilic.

Preparation of nanofibrous materials activated with metal clusters for active and long-lasting air filters

Nanowire poly(vinylidene fluoride) (PVDF) polymer membranes activated with Ag and Zn nanoclusters were prepared using the electrospinning method. The structure of membranes was varied by using different polymer concentrations in N,N-dimethylacetamide, electric field strength, and concentration of AgNO3 and ZnCl2 in an electrospinning solution. Materials synthesised were analysed by nitrogen sorption and mercury intrusion porosimetry, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, thermogravimetry, inductively coupled plasma mass spectroscopy, particle filtration efficiency, and pressure drop methods. The concentration of Ag and Zn nanoclusters in PVDF membranes was established and the influence on nanofibers activity has been discussed. The hydrophobicity of membranes was tested using the wetting (contact) angle measurement method. The human influenza A virus (IAV) A/WSN/1933 (H1N1) strain was used to evaluate the virucidal activity of filtration materials. The virucidal activity increased with Ag nanoclusters concentration in fibres. The most hydrophilic nanofibers with Zn nanoclusters showed very high and practically concentration independent virucidal activity that was two orders of magnitude higher compared to materials activated with Ag nanoclusters.

Prediction of Dielectric Breakdown of OHTL Insulators Using Contact Angle Measurements

Porcelain insulators used in overhead transmission lines (OHTL) are exposed to pollution when operational. To observe the effect of external pollution on these insulators, the relationship between the flashover voltage and surface contamination was studied. The flashover voltage drops sharply when contaminants in the wind are deposited on the surface of the insulators in a humid environment. Under wet conditions, the flashover voltage demonstrates a difference of approximately 10 kV depending on the contamination levels. The higher the equivalent salt deposit density, the lower the contact angle. In particular, the flashover voltage under wet conditions decreases exponentially when the contact angle is below 30°. In this case, the condensation area becomes considerably wider, thus exhibiting the difference in the area of the electrolytic conductive film layer forming the leakage path on the surface. Depending on the equivalent salt deposit density and contact angle, the area of condensation is more than doubled. To measure the level of contamination on the surface using this principle, a contact angle measurement method was adopted to predict the dielectric breakdown of the insulator.

New ellipse-fitting method for contact angle measurement

In this work, the authors examined the commonly used fitting methods for optical contact angle measurement. It was shown that currently, there is no available fitting method that can measure the contact angle of a non-axisymmetric drop without a clear view of the drop baseline. This work contributes to contact angle measurement methods by providing a new ellipse-fitting method. The new method fits the drop profile with a general equation of an ellipse whose major and minor axes are not necessarily parallel and normal with the substrate, respectively. The advantage of this method is that it can measure the contact angle of a non-axisymmetric drop without a clear view of the drop baseline. The measurement results were validated by comparing against the DropSnake and polynomial fitting methods. Generally good agreement was seen, which is important as it validates this method as the only available method for finding the contact angle of a droplet when the contact line is not visible – for example, in a condensation environment where many drops can block the view of each other’s contact line.

An unconventional approach in investigating wettability contact angle measurement in shale resources

Wettability measurement is important in production development to newly discovered as well as mature reservoirs. Evaluating the wettability is exceptionally important (for its significant-yields in hydrocarbon quantities) in oil and gas production schemes for newly discovered reservoirs such as shale reservoirs and other unconventional plays. Shale wettability has its unique fluid-mineral distribution relationships, which makes both pore morphology as well as mineral composition very significant factors controlling its wettability. The complex shale physical, chemical, and crystollgraphical constituent’s mineralogy as well as its physical pore morphology heterogeneity can complicate the wettability measurement further inside the pore structure fabrication, and hence the ultimate oil/gas recovery. The main objective of this study is to investigate the complexity of heterogeneous mineral structure of shale as well as its complex pore structure and its attributes toward the unconventional imaging method of wettability contact angle measurement.

A contribution to flotation technique as a reliable wettability alteration measurement method for carbonate minerals in separation processes involving hydrocarbons, low salinity water and nanofluids

A reliable flotation method was developed and experimentally evaluated as a fast and repeatable quantitative wettability measurement technique for Enhanced Oil Recovery (EOR) purposes by comparing its performance with the well-known and reliable method of contact angle measurement. In both methods, oil-wet carbonate specimens were contacted with brines of different salinities and nanoparticle concentrations, and the trend of test results were compared. In the salinity tests, it was observed that flotation results are in full consistency with contact angle measurements. In both methods, salinity reduction from seawater (SW) to 10 times diluted seawater (TDSW) resulted in reaching the maximum hydrophilicity while further dilution to 40 TDSW hindered the wettability alteration process. Nanofluid tests in both methods were also in great consistency at nanoparticle concentrations below 0.1%wt due to particle stability limitations. Finally, two flotation mechanisms for the oil/water/rock system were introduced and one of them was empirically confirmed.

Contact angle measurement using a Hele-Shaw cell: A proof-of-concept study

Contact angle is an important property to quantify the wettability of a solid surface with a liquid, which characterizes interactions of the solid-liquid pair. Generally, to measure contact angle, special instruments such as a goniometer are necessary, but they are not readily available in certain research settings. In this study, an alternative method to measure contact angle based on a Hele-Shaw cell, microscopy imaging, and image processing is suggested. In this method, a liquid drop is injected into a transparent Hele-Shaw cell, the meniscus of the drop is captured in the top or bottom view using a brightfield microscope, and the contact angle is measured from the captured image based on a geometrical model of the drop in the Hele-Shaw cell. The proposed method was tested using two different liquids (deionized water and glycerol) and two different solid surfaces (polydimethylsiloxane [PDMS] and commercial water-repellent-coated glass) with various gap heights of Hele-Shaw cells and validated in comparison with a goniometer. Our results show that the proposed method could measure contact angles reasonably well. Although the concept of the proposed quick-and-dirty contact angle measurement method was proven in this study, there is still room to improve the accuracy and reliability of the proposed method.

Characterization of microstructure and surface properties of GLC film deposited in plasma nitriding system

Graphite-like carbon films were deposited on silicon substrates in plasma nitriding system with propane and hydrogen. Scanning electron microscope, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscope, and contact angle measurement method were used to investigate the effect of voltage, duty cycle, and gas composition on the growth thickness, hydrogen content, atomic bond structure, surface roughness, surface morphology, and wettability of the films. It is shown that the thickness of the films decreased with the voltage and duty cycle increasing. The voltage, duty cycle and gas composition have a significant effect on the sp2/sp3 bonds and hydrogen content, which can produce the a-C:H films characterized by sp2 bonding (over 70%). As the voltage and duty cycle improved, the surface morphology of the film progressed from a rugged surface with wide hillsides to a flat level surface. This work will provide a novel method to produce graphite-like carbon films with lubricating and anti-wear properties and give direction on designing high-performance tribo-systems for industrial applications.

Affinity Analysis of Photoacid Generator in the Thin Film of Chemical Amplification Resist by Contact Angle Measurement

In extreme ultraviolet (EUV) lithography development, the reduction of line width roughness (LWR) is a one of the significant issues. It has been reported that the LWR of photoacid generator (PAG) bounded resist is lower than that of PAG blended resist. It is considered that the chemical composition distribution of PAG bounded resist is more uniform than PAG blended resist. However, it has not been evaluated systematically and experimentally. In this study, we introduced the contact angle measurement method for the evaluation of the chemical composition distribution between PAG blended resist and PAG bounded resist. It is clarified that the resist thin film has a different chemical composition distribution from the center to the outside of wafer regardless of the type of resists. In particular, the chemical composition distribution of the bounded resist showed the opposite behavior to that the blended one.

Kinetics of Adhesion Staphylococcus aureus on Glass in the Presence of Sodium Lauryl Sulfate

AbstractBacterial contamination of surfaces is a natural and spontaneous process that often results in the formation of biofilms. The extracellular matrix of biofilm is mostly composed of proteins, polysaccharides, and extracellular DNA and is responsible for the strong persistent ability of biofilm in the food industry. Despite cleaning and disinfection processes, persistent bacteria cause a major problem in food processing environments. Synthetic surfactants, mainly anionic surface‐active agent, are commonly used as detergents, foaming agents, wetting agents, emulsifiers, and dispersants. Their tendency to adsorb to surfaces and interfaces and modify their surface tension, is considered among their main properties. They also have the ability to attach to bioactive macromolecules such as proteins, peptides, and DNA causing cell membrane damage. In order to estimate the adhesion kinetic and proliferation of pathogenic bacteria Staphylococcus aureus, the surface of glass was coated with anionic surfactant Sodium Lauryl Sulfate (SLS). Moreover, SLS was added in suspension with the culture medium. The physicochemical properties of the material were calculated using the contact angle measurement method and bacterial hydrophobicity using the microbial adhesion to hydrocarbons (MATH) test. The obtained results showed that the number of adhering cells increased gradually as a function of time. However, changing the surface properties of the glass and S. aureus has affected the rate of adherent cells with time as well as their organization. SLS inhibited the attachment of cells, whether it is added with the microbial suspension or at the surface of the support. Generally, the present article points to a relationship between the microbial adhesion, the surface chemistry of the solid material and the bacteria, and the suspension properties.

Enhanced Washburn Method (EWM): A comparative study for the contact angle measurement of powders

Washburn Method (WM) as a typical contact angle measurement (θ) method can be used for assessment of powder wettability (especially representative particle size range for flotation separation). However, as an indirect method, WM has several limitations. This investigation is going to introduce an Enhanced Washburn Method (EWM), which fills the gap of those WM obstacles, and can be applied for the meaningful indirect θ measurement of powders. For such a purpose, the wettability of quartz powders (d80: 62 μm) was measured in the absence and in the presence of the cationic surfactant Flotigam®EDA at pH 10. EWM by using pre-conditioning of hydrophobized particles via unblock capillaries measured the θ of powders in different conditions. Statistical evaluations indicated that EWM could quite accurately measure θ of the hydrophobized powders, where there is a significant coefficient of determination (R2 above 0.96) between EWM outcomes and other examined direct θ measurement methods (the captive bubble and sessile drop methods).

Effects of swelling-clay and surface roughness on the wettability of transitional shale

Wettability in unconventional reservoirs is poorly understood. However, it plays a fundamental role in fluid-rock interactions, and an understanding of wetting behavior is essential for capillary seal assessments and hydrocarbon reserve estimation and recovery in clay-rich reservoirs. In this study, the wetting behavior of transitional Shanxi-Taiyuan shale from the southern North China basin was examined via the contact angle (CA) and spontaneous imbibition (SI) measurement methods. Under water-air-shale conditions, water-wet and neutral-wet behaviors were observed, whereas neutral-wet and oil-wet behaviors were observed under water-oil-shale conditions (Young's equation was used to convert the water-air-shale system to the water-oil-shale system). When the CA method was used, the shale was shown to be hydrophobic, whereas when the SI test was used, the shale was observed to be hydrophilic. The water-air CAs are negatively correlated with the total organic content (TOC), carbonate and clay mineral contents (excluding those of illite). Furthermore, iron-containing compounds, such as pyrite and siderite, were shown to decrease the water wetness. A linear negative correlation was found between the surface roughness and the CA value. The relationship between these parameters can be used to predict the CAs at different surface roughness values for a given sample. The contradictory wetting behaviors between the results of SI and CA methods can be explained by: (i) differences between the CAs formed under water-air-shale conditions and those formed under hydrocarbon-brine-shale conditions; (ii) differences in the surface roughness, which is dependent on the texture and mineralogy of the shale sample; and (iii) clay swelling after water sorption and the formation of microfractures due to water–rock interactions.