Adhesion Parameters Research Articles

Discrimination of adhesion and viscoelasticity from nanoscale maps of polymer surfaces using bimodal atomic force microscopy.

The simultaneous excitation and measurement of two eigenmodes in bimodal atomic force microscopy (AFM) during sub-micron scale surface imaging augments the number of observables at each pixel of the image compared to the normal tapping mode. However, a comprehensive connection between the bimodal AFM observables and the surface adhesive and viscoelastic properties of polymer samples remains elusive. To address this gap, we first propose an algorithm that systematically accommodates surface forces and linearly viscoelastic three-dimensional deformation computed via Attard's model into the bimodal AFM framework. The proposed algorithm simultaneously satisfies the amplitude reduction formulas for both resonant eigenmodes and enables the rigorous prediction and interpretation of bimodal AFM observables with a first-principles approach. We used the proposed algorithm to predict the dependence of bimodal AFM observables on local adhesion and standard linear solid (SLS) constitutive parameters as well as operating conditions. Secondly, we present an inverse method to quantitatively predict the local adhesion and SLS viscoelastic parameters from bimodal AFM data acquired on a heterogeneous sample. We demonstrate the method experimentally using bimodal AFM on polystyrene-low density polyethylene (PS-LDPE) polymer blend. This inverse method enables the quantitative discrimination of adhesion and viscoelastic properties from bimodal AFM maps of such samples and opens the door for advanced computational interaction models to be used to quantify local nanomechanical properties of adhesive, viscoelastic materials using bimodal AFM.

Operating parameter optimization of cell surface hydrophobicity test for ureolytic bacteria

As one of the main non-covalent relations in microbiological-based systems, cell surface hydrophobicity (CSH) can be observed as a relevant parameter for biodegradation capability and suggested bacterial behaviour and biofilm formation during a bioremediation process. On the other hand, the role of ureolytic bacteria in bioremediation has subsequently led to the examination of this bacterial type in different engineering fields. In order to optimize the operating parameters of microbial adhesion to hydrocarbons test (MATH) for ureolytic bacteria, Box?Behnken experimental design was conducted for five ureolytic bacteria isolated from soils, as well as for the reference strain Sporosarcina pasteurii DSM 33. The optimization was completed with and without the essential substrate for the targeted metabolic reaction, with the aim to compare differences in bacterial hydrophobicity. A vortex time of 2 min, a hydrocarbon volume of 0.5 mL, and a phase separation time of 15 min are recommended as MATH operating parameters for all tested ureolytic bacteria. Although all bacteria are hydrophobic, lower CSH values in the presence of urea were observed for the same bacterium, which could be explained by the interaction of urea with the organic phase of the separation system, as well as a rapid ureolysis process that also occurs during the application of ureolytic bacteria in biotechnology systems.

Effects of different types of herbs on colour and texture properties of Kashar cheese

In this study, six types of Kashar cheese, five with added herbs and one without any additives, which is determined as a control sample were produced. Urtica dioica L. (nettle), Petroselinum crispum (parsley), Mentha piperita (mint) and Eruca vesicaria (arugula), Chaerophyllum byzantinum Boiss. (mendek) were added to cheese clot in proportion as 0.1% amounting to 0.1-0.3 cm split particles depending on the milk used. Then, all the cheeses were vacuum-packed and ripened at 7 ±1°C for 3 months, and their L*, a*, b* colour values and textural parameters including resilience, hardness, elasticity, gumminess, cohesiveness, adhesiveness, and chewiness were determined using texture profile analyses (TPA). It was observed that neither cohesiveness, adhesiveness and elastic parameters of texture profile differed in terms of cheese type, nor important statistical difference was identified (P˃0.10), differences regarding the ripening process found out though (P<0.05).

Application of energy efficient materials in reconstruction of buildings and structures of transport infrastructure

The article analyzes in detail the results of the performed reconstruction works with the application of thermosetting polymers. The method of adhesive anchoring of reinforcement rods with fixing them in the concrete body with acrylic glue was carried out on transport infrastructure facilities (railway steam shop and railway itinerary post). It has been determined that strengthening the foundation with application of the thermosetting polymers (adhesive anchor joints) gives a significant reduction in the consumption of concrete, metal and labor costs. The advantage of such acrylic adhesives is the possibility of varying the ratio of monomeric and polymeric part (powder) containing redox system, within acceptable concentrations, without significant changes in adhesion and cohesion parameters. The obtained results are very important in practice, because in the conditions of preparation of the adhesive (especially in construction conditions) it is difficult to determine the exact number of components. The experimental research data can be used for attachment joints projecting and industrial technological lines development, as well as for further polymeric adhesive materials, widely applied in industrial and civil engineering, improvement.

Spherical adhesion contact problem for FGM coating-substrate system

In the present study, the effect of adhesion on axisymmetric contact problem for functionally graded material (FGM) coating-substrate system under the spherical indenter is considered. The linear multi-layered model is applied to model the functionally graded coating with arbitrarily varying material properties. The couple effect of adhesion parameter and gradient index is calculated based on the singular integral equation which can be solved by using the numerical method. The results show that the pull-off force, the contact region and the surface stress distribution between the indenter and surface of FGM coating are affected by adhesion parameter, gradient index and coating thickness.

High Temperature Sealing of Silicon Oxide/Oxide Bonding Interfaces

High temperature (>1000°C) annealing is necessary to completely close a bonding interface. Using interface synchrotron high energy X-ray reflectivity, we have investigated the sealing behavior of silicon thermal oxide/ silicon thermal oxide interfaces, with different surface roughnesses. Interface X-ray reflection is able to measure accurately the width and the depth of the electron density gap across a bonding interface with a sub-nanometer accuracy, whose product is a good marker of the interface closure.The uncomplete closure of the interface is the result of a balance between attractive and repulsive force between the two bonded solids. These two forces depend on the statistics of asperity and on the mechanical behavior of individual asperity [1]. For attraction, at high temperatures, a key factor is the gain of contact surface area which reduces the surface energy due to uncontacted zones. Repulsion is due to compression of contacting asperities. At high temperature, both elastic and plastic behavior can be expected, with some yield of the asperities compressed above the elastic limit.In the elastic solid regime, we have shown that equilibrium distance of rough silicon oxide to rough siliconoxide bonding can be predicted using standard adhesive contact models such as Johnson-Kendall Roberts (JKR) or Deryagin-Müller-Toporov (DMT) with Gaussian roughness statistics[2]. The equilibrium distance is dependent and sensitive to the Fuller Tabor adhesion parameter, θ=E σ3/2 R1/2 / 2γR where E is the Young modulus, σ the mean roughness, R the radius of the asperity, while 2γ is the adhesion energy at contact points. When θ>>1 , the equilibrium distance is large and the contact area is small (unclosed interface) . When θ<<1 the adhesion energy is strong and the system will have a strong tendency to seal.In the plastic regime, both repulsive and attractive curves share the same dependence with distance so that the system is expected to be unstable, between a weakly evolving unsealed interface and a fully sealed interface when the asperity pressure stress is above the elastic limit.The kinetics of the sealing can also be modeled in this case, monitoring the interfacial gap as a function of time (Figure). It is found that the sealing characteristic time scales directly with the silicon oxide viscosity (Figure insert). This dependence can be understood using the plastic asperity contact model, assuming the fluid part flows according to the Stokes equation around asperities.

Simultaneous Determination of Human Erythrocyte Deformability and Adhesion Energy: A Novel Approach Using a Microfluidic Chamber and the "Glass Effect".

The simultaneous determination of adhesion and deformability parameters of erythrocytes was carried out through a microfluidic device, which uses an inverted optical microscope with new image acquisition and analysis technologies. Also, an update of the models describing erythrocyte adhesion and deformation was proposed. Measurements were carried out with red blood cells suspended in saline solution with human serum albumin at different concentrations. Erythrocytes adhered to a glass surface were subjected to different low shear stress (from 0.04 to 0.25 Pa), causing cellular deformation and dissociation. The maximum value obtained of the erythrocyte deformability index was 0.3, and that of the adhesion energy per unit area was 1.1 × 10-6 Pa m, both according to previous works. The obtained images of RBCs adhered to glass reveal that the adhesion is stronger in a single point of the cell, suggesting a ligand migration that concentrates the adhesion in a "spike-like tip" in the cell. Moreover, adhesion energy results indicate that the energy required to separate erythrocytes in media with a lower albumin concentration is greater. Both results could be explained by the mobility of membrane receptors.

Aktivitas Antibakteri Sediaan Gel dari Fraksi Aktif Daun Sintrong (Crassocephalum Crepidioides (Benth) S Moore)

Indonesia is a tropical country that allows bacteria to easily grow and develop, especially in the skin. The drugs used are very diverse, generally from corticosteroids, which have side effects. This encourages the need for research on antimicrobial drugs from natural ingredients such as herbs that have high potency and relatively low side effects. Sintrong plants (Crassocephalum crepidioides (Benth.) S. Moore) are found in Parmeraan Village, Dolok District, North Padang Lawas Regency, North Sumatra Province. This plant is thought to contain alkaloid compounds and tannins as antimicrobials. This research method is an experimental study with the maceration method of ethanol extract and fractionation of n-hexane, ethyl acetate, phytochemical screening, making topical gels 20%, 10%, and 5% with parameters of pH, homogeneity, viscosity, dispersibility and adhesion as well as Antibacterial test against pure cultured bacteria using agar diffusion method using metal buffer, the bacteria used were gram-positive bacteria (Staphylococcus aureus ATCC 29737) and gram-negative bacteria (Escherichia coli ATCC 10536). The results showed that the ethanol extract of Sintrong leaves can be formulated in the form of a gel. The results of the evaluation that have been carried out on the methanol extract gel of Sintrong leaves show that the preparation has met the gel requirements. The formula that has the best antibacterial activity is Formula 1 which provides an inhibitory diameter of 17.10 mm and 18.75 mm for Escherichia coli and Staphylococcus aureus bacteria.

The Effect of Protein Source on the Physicochemical, Nutritional Properties and Microstructure of High-Protein Bars Intended for Physically Active People.

The purpose of this study was to investigate the effect of protein sources (algae, pumpkin, wheat, sunflower, rice, soy, hemp, pea, and whey) on selected physicochemical, nutritional, and structural parameters of high-protein bars. Texture properties, such as hardness, fracturability, cohesiveness, and adhesiveness, have changed depending on the type of protein used. A significant increase, in particular the hardness parameter relating to the control sample (whey protein concentrate—WPC80), was noted for bars containing algae, sunflower, and wheat proteins, with high values of the adhesiveness parameter concurrently. The use of proteins from algae, pea, and wheat resulted in a significant reduction in the water activity of the finished product compared to WPC80. Bars made with the use of wheat, hemp and pumpkin proteins had noticeably higher viscosities than other samples. Color of the tested bars measured by means of Computer Vision System (CVS) was from light cream (soy, pea) to dark green (hemp, pumpkin). Bars prepared of wheat and algae proteins had the highest nutritional value, while the lowest one was recorded in products containing sunflower and hemp proteins. There was a clear differentiation of amino acids (g/100 g) and microstructure in bars depending on the type of protein used. However, a slight similarity can be found between whey and soy proteins (amino acids) and between whey and sunflower proteins (microstructure). Obtained results suggest that selection of the right type of protein for a given application may have a significant impact on the physicochemical features and microstructure of high-protein bars and their nutritional values.

Deterministic normal contact of rough surfaces with adhesion using a surface integral method.

The fundamental problem of adhesion in the presence of surface roughness and its effect on the prediction of friction has been a hot topic for decades in numerous areas of science and engineering, attracting even more attention in recent years in areas such as geotechnics and tectonics, nanotechnology, high-value manufacturing and biomechanics. In this paper a new model for deterministic calculation of the contact mechanics for rough surfaces in the presence of adhesion is presented. The contact solver is an in-house boundary element method that incorporates fast Fourier transform for numerical efficiency. The adhesive contact model considers full Lennard-Jones potentials and surface integration at the asperity level and is validated against models in the literature. Finally, the effect of surface roughness on the adhesion between surfaces was studied, and it was shown that the root mean square gradient of surface roughness can change the adhesive pressures irrespective of the root mean square surface roughness. We have tested two adhesion parameters based on Johnson's modified criteria and Ciavarella's model. We showed that Civarella's model introduces the most reasonable criteria suggesting that the RMS roughness and large wavelength of surfaces roughness are the important parameters of adhesion between rough surfaces.

Interfacial interactions and properties of cellular structured polyurethane nanocomposite based on carbonaceous nano‐fillers

AbstractIn this article, we have studied the effect of carbonaceous nanofillers viz. fullerenol (0D), carboxylated multi‐wall carbon nanotube (MWCNT, 1D), hydroxylated graphene (2D) and combination of carboxylated CNT and hydroxylated graphene as 3D in thermoplastic polyurethane on the tensile properties of the fabricated cellular structures. The concentration of nano‐fillers was varied as 0.1, 1, and 5 wt%. Tensile properties of the nanocomposite cellular structures were measured as per ASTM D882 at 20°C (below glass transition temperature, Tg) and 40°C (above Tg). The results have shown that the tensile strength was found to increase by 200%–300% and the tensile modulus was found to increase by 150%–300% for 2D and 3D nano‐fillers while significantly poor results were observed for 0D. However, the test data tensile strength and modulus showed marginal increase at 20°C and marginally low at 40°C for 1D filler. The interfacial adhesion was calculated by using experimental tensile data and the predictive models. The interfacial adhesion parameter (Bσ) calculated using Pukanszky equation was found significantly higher value for 2D (Bσ20 = 195.8) and 3D (Bσ20 = 192.0) fillers while poor adhesion was observed for 0D (Bσ20 = −81.6) fillers. The developed cellular structured materials were also evaluated by attenuated total reflection Fourier transform IR spectra, differential scanning calorimetry, X‐ray diffraction, scanning electron microscope, and transmission electron microscope.

Collision-induced breakage of agglomerates in homogenous isotropic turbulence laden with adhesive particles

Abstract

Changes in cell wall components and polysaccharide-degrading enzymes in relation to differences in texture during sweetpotato storage root growth

Sweetpotato has special texture characteristics, which directly affect the eating quality and post-production processing quality of sweetpotato. To investigate the texture change mechanism of sweetpotato during the growth process, this study selected two varieties with significant differences in texture from 35 varieties. The storage roots were sampled at 50, 80, 110, and 140 days after planting. Measure the texture parameters, the cell wall composition content, cell wall-related enzyme activities and the expression of expansin genes of sweetpotato storage roots. The results show that the hardness, adhesiveness and chewiness parameters of ‘Yushu No 10′ were significantly lower than those of ‘Mianfen No 1′, they have significantly different texture properties. In terms of cell wall composition, the soluble pectin content of ‘Yushu No 10′ was more than twice that of ‘Mianfen No 1′, whereas the insoluble pectin content was lower than that of ‘Mianfen No 1′, with the cellulose content of ‘Yushu No 10′ being significantly higher than that of ‘Mianfen No 1′. In terms of cell wall-related enzymes, ‘Yushu No 10′ hardness gumminess and chewiness had a significant correlation with hemicellulose activity, and ‘Mianfen No 1′ had insignificant correlation with four cell wall-related enzymes. Expansin genes were also expressed differently during the various stages of root tubers expansin. The expressions of IbEXP1, IbEXP2 and IbEXPL1 were significantly correlated with the changes in cell wall component content, and were related to the qualitative structure changes. The research conclusion shows that the texture changes during the growth of sweetpotato are related to cell wall composition, cell wall-related enzyme activity changes, and the expression of expansin genes. This study provides theoretical guidance for in-depth study of texture changes of sweetpotato, post-harvest processing and utilization and quality improvement of storage roots.

Finite element simulation of friction and adhesion attributed contact of bio-inspired gecko-mimetic PDMS micro-flaps with SiO2 spherical surface

The remarkable tribological attributes of the gecko feet have grown much interest in the field of biomimetic tribology over the past two decades. It has been shown that the complexity of friction and adhesion phenomena made it difficult to transfer these exceptional properties into fully functional smart, dry, micro patterned adhesives. The latter, combined with the relative lack of literature on computational oriented studies on these phenomena, is the motive of the current work. Here, a 2D time-dependent finite element model of friction and adhesion attributed contact of polydimethysiloxane (PDMS) micro flaps with a smooth SiO2 spherical surface is presented. The model is tested through simulations concerning changes in the disc curvature, the flap density, as well as different disc mounting heights, representing the effect of preload. Furthermore, the effect of tribological parameters of adhesion and friction coefficient is discussed. Finally, the effect of the use of two hyperelastic material models was examined.

Techno-functional characterization and biological potential of Agave americana leaves: Impact on yoghurt qualities

This study aims to characterize the Agave americana leaves powder (AALP) and valorize its soluble extract (soluble extract Agave americana leaves (SEAAL)) on a steamed yoghurt. During 21 days of storage, the analyses of pH, titratable acidity, syneresis, viscosity, color and texture of SEAAL at 1, 2 and 3% on refrigerated yoghurt were performed. The results revealed that AALP had a high level in mineral composition and richness in total sugars and protein with 55.68 and 34.56%, respectively. Concerning the techno-functional and biological properties, AALP had a higher (p < 0.05) water holding capacity (WHC), oil holding capacity (OHC) and swelling capacity (SWC), exhibiting a good anti-food-borne bacterial activity, especially against Salmonella typhymurium. The incorporation of SEAAL extract into yoghurt was also investigated to determine the rheological properties, instrumental color (L*, a* and b*) and textural (hardness, cohesivness, adhesiveness and elasticity) parameters, as well as sensory attributes using a 5-point hedonic scale. Generally, SEAAL improved the color and texture of the product by decreasing the syneresis and increasing the viscosity compared to the control samples. Similarly, the yoghurt enriched with 2% of SEAAL was the most appreciated by the tasting panel. Given its richness in nutritious ingredients, SEAAL could be a promising constituent for improving the quality of yoghurt. Furthermore, SEAAL could be a strong candidate for future applications in a wide range of healthy dairy products.

Determination of the effects of spices on the ripening of traditional Circassian cheese

In this study, five types of Circassian cheese, including the control sample, were produced using the traditional method. While the control sample had no spices, black pepper, coriander, basil, and black cumin spices were added to the curd at 0.5% on milk basis. The cheeses were vacuum packed and ripened at 7 ± 1°C for 90 days. Dry matter, fat, pH, titratable acidity, salt, total protein, ripening index, nonprotein nitrogen ratio (NPN), electrophoretic casein fractions, textural properties, and sensory analysis were performed on the 2nd, 30th, 60th, and 90th day of ripening. The data obtained were compared statistically in terms of cheese type and ripening time. It was found that there was no significant difference in the values of cohesion, adhesion, elasticity, and springiness parameters during the ripening period. However, there were statistically significant differences in all other values p < .01). Considering the electrophoretograms, black cumin, and black pepper added cheeses had relatively higher proteolysis rates. Sensory evaluation indicated that the 60 day-ripened cheeses were more appreciated than the fresh and 90 day-ripened cheeses when general acceptability scores were considered. Moreover, it was determined that the control cheese and black cumin added one had higher sensory scores. Practical applications Spices or herb extracts are used to provide a variety of flavors in cheeses and make them more attractive to consumers, increase fermentation and metabolites of cheese, thereby extending their shelf life. In this study, black pepper, coriander, basil, and black cumin were added to the Circassian cheese curd, and the changes with its storage were investigated. This study will contribute to the limited literature of Circassian cheese, a traditional cheese while increasing its popularity. Also, the utilization of selected spices will not only help market expansion by providing novel products, but also producers by accelerating the ripening process.

Investigation of Cancer Cell Migration and Proliferation on Synthetic Extracellular Matrix Peptide Hydrogels.

Chemical and mechanical properties of a tumor microenvironment are essential players in cancer progression, and it is important to precisely control the extracellular conditions while designing cancer in vitro models. The study investigates synthetic hydrogel matrices from multi-arm polyethylene glycol (PEG) functionalized with collagen-like peptide (CLP) CG(PKG)4(POG)4(DOG)4 alone and conjugated with either cell adhesion peptide RGD (mimicking fibronectin) or IKVAV (mimicking laminin). Human glioblastoma HROG36, rat C6 glioma cells, and A375 human melanoma cells were grown on the hydrogels and monitored for migration, proliferation, projected cell area, cell shape index, size and number, distribution of focal contacts in individual cells, and focal adhesion number. PEG-CLP-RGD induced migration of both glioma cell lines and also stimulated proliferation (assessed as metabolic activity) of HROG36 cells. Migration of C6 cells were also stimulated by PEG-CLP-IKVAV. These responses strongly correlated with the changes in adhesion and morphology parameters of individual cells – projected cell area, cell shape index, and focal contact number. Melanoma A375 cell proliferation was increased by PEG-CLP-RGD, and this was accompanied by a decrease in cell shape index. However, neither RGD nor IKVAV conjugated to PEG-CLP stimulated migratory capacity of A375 cells. Taken together, the study presents synthetic scaffolds with extracellular matrix (ECM)-mimicking peptides that allow for the exploration of the effect of ECM signaling to cancer cells.

Adhesive Interaction of Elastic Bodies with Regular Surface Relief

This paper focuses on adhesive interaction between an axisymmetric indenter and an elastic half-space taking into account the surface microrelief in the form of regularly located identical asperities covering the indenter. The microlevel contact between the asperities system and the elastic half-space is considered discrete. The solution to the problem at the macrolevel is constructed using the dependence of the effective specific adhesion force on the value of the nominal gap obtained by solving the problem at the microlevel. The constructed solution makes it possible to model the influence of microgeometry and adhesion parameters on the contact interaction of elastic bodies at the macrolevel.

The fractal approach and the effect of nanoadhesive in polymer nanocomposites

Currently, a thermodynamic fractal model of the formation of an interphase layer in polymer nanocomposites is becoming widespread. In accordance with this model, the surface of nanoparticles with which the polymer matrix interacts is a fractal object. This means that the number of contact points depends on the dimension of the nanoparticle surface accessible for such a contact (unshielded). The dependences of the interfacial adhesion parameter on the coefficients of thermal expansion, nanoparticle size, fractal dimension of the nanoparticle surface, etc. have been obtained. In polymer nanocomposites, the level of interfacial adhesion, in comparison with microcomposites, is an order of magnitude higher. This phenomenon is called the nanoadhesion effect and it has an absolutely dimensional character, i.e. takes place when polymers are filled with nanosized particles. Currently, to assess the level of interaction between the phases “nanoparticle-polymer” use the parameter of the level of interfacial adhesion, which is calculated by the values of three quantities: the actual coefficient of linear thermal expansion of the investigated nanocomposite, the coefficients of linear thermal expansion, calculated by the rule of mixtures and by the Turner formula. Considering a nanoparticle as a fractal object, it is possible to estimate the influence of the nanoparticle size, fractal dimension of the nanoparticle surface, and the volumetric content of the filler on the level of interfacial adhesion in the nanocomposite. The article investigates the influence of the size of nanoparticles and the fractal dimension of the surface of aluminum nanoparticles on the parameter of interfacial adhesion. It has been established that filling the polymer matrix with aluminum nanoparticles with the size rn = 35nm, fractal dimension of the nanoparticle ds = 3,3 surface will provide the effect of nanoadhesion in the new nanocomposite based on the elastomer. Experimental studies have confirmed the presence of the nanoadhesion effect in the nanocomposite based on the F-40C elastomer, which manifested itself in an increase in its deformation and strength properties. The optimal composition of the nanocomposite, which provides the highest deformation and strength properties of the material, has been determined.

On the features of production, design and reliability assessment of enclosing composite structures with effective thermal insulation

The article gives priority results on the production, design and assessment of the reliability of composite structures made of materials with energy-saving thermal insulation, physical heterogeneity of the parameters and the adhesion strength of the thermal insulation to the metal finishes. Addresses experimental results of changes in bulk mass, tensile and compressive strength, elastic properties in tension and compression along the thickness of the products perpendicular (⊥) and parallel to (ǁ) the product plane. Establishes the parameters of adhesion to the upper and lower finishes and their probability distributions according to Gauss, Gram-Charles, Pearson, Weibull and the log-normal law. This allows to set the standard values of thermal insulation. The article is aimed at the maximum use in buildings of sandwich panels of full factory production.