Surface Interaction Properties Research Articles

In Situ Functionalization of Polar Polythiophene-Based Organic Electrochemical Transistor to Interface In Vitro Models.

Organic mixed ionic-electronic conductors are promising materials for interfacing and monitoring biological systems, with the aim of overcoming current challenges based on the mismatch between biological materials and convectional inorganic conductors. The conjugated polymer/polyelectrolyte complex poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT/PSS) is, up to date, the most widely used polymer for in vitro or in vivo measurements in the field of organic bioelectronics. However, PEDOT/PSS organic electrochemical transistors (OECTs) are limited by depletion mode operation and lack chemical groups that enable synthetic modifications for biointerfacing. Recently introduced thiophene-based polymers with oligoether side chains can operate in accumulation mode, and their chemical structure can be tuned during synthesis, for example, by the introduction of hydroxylated side chains. Here, we introduce a new thiophene-based conjugated polymer, p(g42T-T)-8% OH, where 8% of the glycol side chains are functionalized with a hydroxyl group. We report for the first time the compatibility of conjugated polymers containing ethylene glycol side chains in direct contact with cells. The additional hydroxyl group allows covalent modification of the surface of polymer films, enabling fine-tuning of the surface interaction properties of p(g42T-T)-8% OH with biological materials, either hindering or promoting cell adhesion. We further use p(g42T-T)-8% OH to fabricate the OECTs and demonstrate for the first time the monitoring of epithelial barrier formation of Caco-2 cells in vitro using accumulation mode OECTs. The conjugated polymer p(g42T-T)-8% OH allows organic-electronic-based materials to be easily modified and optimized to interface and monitor biological systems.

Insight into Virulence and Mechanisms of Amphotericin B Resistance in the Candida haemulonii Complex.

The Candida haemulonii complex includes emerging opportunistic human fungal pathogens with documented multidrug-resistance profiles. It comprises Candida haemulonii sensu stricto, Candida haemulonii var. vulnera, Candida duobushaemulonii, Candida pseudohaemulonii, and Candida vulturna. In recent years, rates of clinical isolation of strains from this complex have increased in multiple countries, including China, Malaysia, and Brazil. Biofilm formation, hydrolytic enzymes, surface interaction properties, phenotype switching and cell aggregation abilities, extracellular vesicles production, stress response, and immune evasion help these fungi to infect the host and exert pathological effects. Multidrug resistance profiles also enhance the threat they pose; they exhibit low susceptibility to echinocandins and azoles and an intrinsic resistance to amphotericin B (AMB), the first fungal-specific antibiotic. AMB is commonly employed in antifungal treatments, and it acts via several known mechanisms. Given the propensity of clinical Candida species to initiate bloodstream infections, clarifying how C. haemulonii resists AMB is of critical clinical importance. This review outlines our present understanding of the C. haemulonii complex's virulence factors, the mechanisms of action of AMB, and the mechanisms underlying AMB resistance.

Spatial evolution characteristics of asphalt surface structure and its influence on surface interaction properties

Air-asphalt surface structure (asphalt surface structure) is widely found in asphalt mixture and is the main structure that directly interacts with air, precipitation and sunlight. To explore the physicochemical properties of asphalt surface structure, the spatial evolution characteristics and interaction properties were studied by combining theory, test and simulation. Firstly, the gestation, generation and development of asphalt surface structure were explained theoretically, and the categories of asphalt surface structure were proposed. Secondly, the spatial evolution characteristics of asphalt surface structure were analyzed by the combination of macro and micro tests. Finally, the relationship between asphalt surface structure and air (N2, O2) and precipitation (H2O) was discussed by using molecular dynamics. It was found that, theoretically, asphalt surface structure can be divided into "initial surface structure", "stable surface structure" and "aged surface structure", and the "stable surface structure" is the ideal surface state. The low temperature environment is conducive to the adsorption of air (N2, O2) by the asphalt surface structure, the "initial surface structure" has a relatively high adsorption interaction capacity. Additionally, the interaction between precipitation and asphalt surface structure is gradually enhanced with the increase of temperature, and the interaction between "aged surface structure" and precipitation is relatively stronger. The study further expands the exploration of asphalt surface structure and provides a theoretical explanation for asphalt aging behavior.

A method for the experimental characterisation of novel drag-reducing materials for very low Earth orbits using the Satellite for Orbital Aerodynamics Research (SOAR) mission

The Satellite for Orbital Aerodynamics Research (SOAR) is a 3U CubeSat mission that aims to investigate the gas–surface interactions (GSIs) of different materials in the very low Earth orbit environment (VLEO), i.e. below 450 km. Improving the understanding of these interactions is critical for the development of satellites that can operate sustainably at these lower orbital altitudes, with particular application to future Earth observation and communications missions. SOAR has been designed to perform the characterisation of the aerodynamic coefficients of four different materials at different angles of incidence with respect to the flow and at different altitudes in the VLEO altitude range. Two conventional and erosion-resistant materials (borosilicate glass and sputter-coated gold) have first been selected to support the validation of the ground-based Rarefied Orbital Aerodynamics Research (ROAR) facility. Two further, novel materials have been selected for their potential to reduce the drag experienced in orbit whilst also remaining resistant to the detrimental effects of atomic oxygen erosion in VLEO. In this paper, the uncertainty associated with the experimental method for determining the aerodynamic coefficients of satellite with different configurations of the test materials from on-orbit data is estimated for different assumed gas–surface interaction properties. The presented results indicate that for reducing surface accommodation coefficients the experimental uncertainty on the drag coefficient determination generally increases, a result of increased aerodynamic attitude perturbations. This effect is also exacerbated by the high atmospheric density at low orbital altitude (i.e. 200 km), resulting in high experimental uncertainty. Co-rotated steerable fin configurations are shown to provide generally lower experimental uncertainty than counter-rotated configurations, with the lowest uncertainties expected in the mid-VLEO altitudes (sim300 km). For drag coefficient experiments, configurations with two fins oriented at 90^{circ } were found to allow the best differentiation between surfaces with different GSI performance. In comparison, the determination of the lift coefficient is found to be improve as the altitude is reduced from 400 to 200 km. These experiments were also found to show the best expected performance in determining the GSI properties of different materials. SOAR was deployed into an orbit of 421 km times 415 km with 51.6^{circ } inclination on 14 June 2021. This orbit will naturally decay allowing access to different altitudes over the lifetime of the mission. The results presented in this paper will be used to plan the experimental schedule for this mission and to maximise the scientific output.

Identification of unknown object properties based on tactile motion sequence using 2-finger gripper robot

The purpose of service robots is to work and handle a wide range of objects in a human environment. Therefore, they must have the ability to grasp unknown objects with the appropriate force, by dynamically identifying their stiffness, mass, and surface-interaction properties. To ensure the successful grasping of unknown objects, it is significant to estimate the object response properties. In this paper, the cognitive functions to efficiently perform such operations with only tactile motion data and supervised learning using limited data, have been demonstrated. The study uses pinch-grasping performed by a 2-fingered robot experimental setup with a pre-designed motion sequence, over 7 different objects having a wide range of properties to capture the motion data. The proposed approach avails pre-processed motion data to train neural networks for accurately predicting object response properties for 3 unseen test objects. We have done a comparative study among three neural network architectures CNN, LSTM, and CNN-LSTM and we found that novel CNN-LSTM outperforms the other two models in terms of accuracy. The CNN-LSTM regression model achieves 0.98 and 0.97 of R2 value for the prediction of stiffness and mass, respectively and the CNN classification model achieves 94% of accuracy for the surface interaction classification.

Study on alkylated Schiff base of a triazole with 3, 5-di-tert-butyl-4-hydroxybenzaldehyde as a novel multifunctional lubricant additive

A novel triazole derived multifunctional lube additive (MFA) denoted as TBB was designed and synthesized for improved metal surface interaction properties and inhibiting lubricant degradation. At first, two hindered phenolic moieties were coupled with the heterocyclic 3,5-diamino-1,2,4-triazole framework by the reaction with 3, 5-di-tert-butyl-4-hydroxybenzaldehyde to give the intermediate Schiff base followed by alkylation through the reaction of bromododecane for better solubility in polyol base oil. After molecular characterization, the TBB performance evaluation for the lubricity and antioxidant characteristics was done following the standard test methods in the polyol. At a low concentration of 1000 ppm, the average wear scar diameter and average friction coefficient was reduced by 16.92% and 64.39% respectively while the RBOT time was increased by 70.76% at 5000 ppm concentration with respect to polol base oil. The standard corrosion testing procedures were used for evaluating the anti-corrosion potential of additive TBB in terms of weight loss, corrosion rate, and penetration rate which were found to be reduced at 5000 ppm concentration to the values as 0.01 ± 0.01 mg, 0.01 ± 0.005 mdd, and 0.001 ± 0.001 mpy from the 0.60 ± 0.04 mg, 0.62 ± 0.03 mdd, and 0.114 ± 0.009 mpy respectively for blank polyol. So TBB showed moderate efficiency as a lubricity improver but showed excellent antioxidant and anti-corrosion additive properties.

Numerical model of fiber wetting with finite resin volume

AbstractThe partial wetting of cylindrical surfaces is encountered in many industrial applications such as composites manufacturing, MEMS, hair care products, and textile engineering. Understanding the impact of key parameters such as resin and fiber surface interaction properties and the geometric arrangement of the fibers on wetting would lead to tailoring a desired interface between the resin and the fiber surface. A three-dimensional model of resin wetting a single fiber is presented. This model is then extended to study a finite volume of resin wetting fibers in square and triangular packing arrangements. The impact of changing wetting properties and fiber volume fraction is examined for each packing arrangement.

Velocity distribution and velocity correlation of mixture of gases in a nanochannel

Molecular dynamics study of non-reacting and disparate mass binary gas mixture is conducted. To investigate the gas–surface interaction properties of the gas mixture, in non-continuum regime, the rarefied gas confined in a nanochannel is considered. While keeping the bulk number density a constant, the interaction properties of gas mixtures at different molar concentration of individual components are determined. The study discusses the calculation of accommodation coefficients and prediction of the reflected gas distribution using accommodation coefficients. The Maxwell-type model that use calculated values of accommodation coefficients accurately predicts the reflected tangential and normal distributions. The model is validated for different wall-fluid conditions. The velocity correlation of individual gases demonstrates that the individual components of gas mixture are accommodated in different proportion. The result from the study will be beneficial in the analysis and development of potential applications involving the flow of gas mixture in a nanochannel.

New interpretations of gripping force tests for lined pipes

Surface interaction properties between the backing steel and liner in lined pipes are important features in terms of understanding the mechanical behavior of lined pipes. Presently API 5LD recommends a gripping force test to classify the surface interaction properties between the liner and the backing steel. In this paper, several details involving the influence of axial and hoop stress interaction, friction behavior and the influence of free boundaries are investigated in testing contexts. Published results using different testing regimes have been re-investigated in order to show the effects of accounting for axial strain release close to free boundaries, axial and hoop stress interaction and different friction behaviors. It has clearly been demonstrated that these effects must be accounted for when trying to accurately quantify surface interaction properties between liners and backing steels in physical testing contexts.

Confinement induced lateral segregation of polymer coated nanospheres

The equilibrium structures of polymers end-tethered to nanoparticles or to nanomicelles interacting with surfaces have been studied theoretically. Polymer chains chemically grafted to nanoparticles are laterally immobile. On the other hand, nanosized polymer micelles formed by polymer chains conjugated with lipids, have end-tethered chains that are laterally mobile within the self-assembled structure. Using a molecular theory, we investigated the influences of the mobile nature of the tethered chains and the nanoscale dimension of the anchoring surface on the structures and interactions of the polymers during the process of binding of the nanoparticle to a surface. We show that polymer chains with bidisperse molecular weight distributions end-tethered to a nanomicelle/nanoparticle surface segregate upon approach to a surface. The shorter chains preferentially locate in the vicinity of the surface, while the longer ones are excluded from the region between the micelle and the surface and thus become more concentrated on the opposite side of the micelle surface. The extent of this segregation is controlled by the overall surface coverage and compositions of the tethered chains, and the sizes of the short and long chains. Combining lateral mobility of the polymer tether with an end-binding capability of the chain (e.g., through a ligand–receptor interaction) can give rise to an enhancement of the interaction of the polymer nanoparticle with a surface. The results demonstrate that laterally mobility of tethered chains is an important aspect that needs to be taken into account in designing polymeric nanoparticles with enhanced surface interaction properties.

Slip flow and heat transfer in rectangular and circular microchannels using hybrid FE/FV method

SUMMARYRarefied gas flows typically encountered in MEMS systems are numerically investigated in this study. Fluid flow and heat transfer in rectangular and circular microchannels within the slip flow regime are studied in detail by our recently developed implicit, incompressible, hybrid (finite element/finite volume) flow solver. The hybrid flow solver methodology is based on the pressure correction or projection method, which involves a fractional step approach to obtain an intermediate velocity field by solving the original momentum equations with the matrix‐free, implicit, cell‐centered finite volume method. The Poisson equation resulting from the fractional step approach is then solved by node based Galerkin finite element method for an auxiliary variable, which is closely related to pressure and is used to update the velocity field and pressure field. The hybrid flow solver has been extended for applications in MEMS by incorporating first order slip flow boundary conditions. Extended inlet boundary conditions are used for rectangular microchannels, whereas classical inlet boundary conditions are used for circular microchannels to emphasize on the entrance region singularity. In this study, rarefaction effects characterized by Knudsen number (Kn) in the range of 0 ⩽ Kn ⩽ 0.1 are numerically investigated for rectangular and circular microchannels with constant wall temperature. Extensive validations of our hybrid code are performed with available analytical solutions and experimental data for fully developed velocity profiles, friction factors, and Nusselt numbers. The influence of rarefaction on rectangular microchannels with aspect ratios between 0 and 1 is thoroughly investigated. Friction coefficients are found to be decreasing with increasing Knudsen number for both rectangular and circular microchannels. The reduction in the friction coefficients is more pronounced for rectangular microchannels with smaller aspect ratios. Effects of rarefaction and gas‐wall surface interaction parameter on heat transfer are analyzed for rectangular and circular microchannels. For most engineering applications, heat transfer is decreased with rarefaction. However, for fluids with very large Prandtl numbers, velocity slip dominates the temperature jump resulting in an increase in heat transfer with rarefaction. Depending on the gas‐wall surface interaction properties, extreme reductions in the Nusselt number can occur. Present results confirm the existence of a transition point below and above wherein heat transfer enhancement and reduction can occur. Copyright © 2011 John Wiley & Sons, Ltd.

Polymeric coatings on micro- and nanometric particles for bioapplications

Particles and notably magnetic particles are used more and more extensively in bioanalytical processes today owing to their ability to considerably facilitate the development of protocols (e.g., easy rinsing and exchange of buffers) and allow miniaturization. Such protocols largely combine the advantages of heterogeneous and homogeneous assays. Applications of these particles, e.g., in protein or nucleic acids purification, immunoassays, or enzymatic microreactors, are developing rapidly, as reflected by the number of commercial kits that are regularly launched. The particles are also increasingly used in microfluidics, in which their potential for miniaturization is at its best. For optimal applications, however, and notably for the analysis and biomolecules and biological samples that are often complex, mastering the interactions between various molecules—particularly biopolymers such as nucleic acids and proteins and the particle surface—and the grafting of active compounds onto the particles is critical and is indeed the major bottleneck to success. These surface interaction properties are responsible for the direct performance of the particles, such as load capacity and kinetics. Most often, however, the bottlenecks to development and key features for performance lie in mastering the surface properties of the grafted active compounds. These properties are responsible for the intrinsic performance, such as load capacity or reaction kinetics, and are also crucial for the control of spurious effects such as nonspecific adsorption or loss of colloidal stability. By providing an intermediate layer between the particle and its environment, that can be tailored both physically and chemically, polymer coatings offer a very powerful tool for controlling the surface properties of micro- and nanoparticles and for their biofunctionalization. Intense research is being performed in this area, stimulated by the strong potential applications mentioned above, and by the recent development of numerous new chemical routes that simplify the synthesis/grafting of polymers, such as controlled radical polymerization methods or click chemistry. We provide here a general review of the field. We first give a general overview of the main features and properties of micro- and nanoparticles that are important for bioapplications, such as specific surface area, surface charge, zeta potential, and colloidal stability. We then summarize the different particle morphologies and the configurations that polymers can adopt on their surfaces, from a structural and physical point of view. We also describe the different strategies that can be used to cover particles with polymers, including physisorption, covalent grafting, or direct polymerization onto the particle. This is followed by a section dedicated to the different characterization methods that can be used to master the development of coating protocols, and to control the final properties. We end with a description of a few typical applications, in which the consequences and importance of the different parameters described in the review are exemplified and discussed.

Cross-species analysis of the glycolytic pathway by comparison of molecular interaction fields

The electrostatic potential of an enzyme is a key determinant of its substrate interactions and catalytic turnover. Here we invoke comparative analysis of protein electrostatic potentials, along with sequence and structural analysis, to classify and characterize all the enzymes in an entire pathway across a set of different organisms. The electrostatic potentials of the enzymes from the glycolytic pathway of 11 eukaryotes were analyzed by qPIPSA (quantitative protein interaction property similarity analysis). The comparison allows the functional assignment of neuron-specific isoforms of triosephosphate isomerase from zebrafish, the identification of unusual protein surface interaction properties of the mosquito glucose-6-phosphate isomerase and the functional annotation of ATP-dependent phosphofructokinases and cofactor-dependent phosphoglycerate mutases from plants. We here show that plants possess two parallel pathways to convert glucose. One is similar to glycolysis in humans, the other is specialized to let plants adapt to their environmental conditions. We use differences in electrostatic potentials to estimate kinetic parameters for the triosephosphate isomerases from nine species for which published parameters are not available. Along the core glycolytic pathway, phosphoglycerate mutase displays the most conserved electrostatic potential. The largest cross-species variations are found for glucose-6-phosphate isomerase, enolase and fructose-1,6-bisphosphate aldolase. The extent of conservation of electrostatic potentials along the pathway is consistent with the absence of a single rate-limiting step in glycolysis.

Comparative Analysis of the Surface Interaction Properties of the Binding Sites of CDK2, CDK4, and ERK2

Recently developed hydrogen-bonding and hydrophobic analysis algorithms were used to investigate the interaction properties of the ATP binding sites of CDK2, CDK4, and ERK2. We were able to prioritise those hydrogen-bonding groups that are observed to bind the native ATP ligand, as well as to identify other important groups found to bind inhibitors of these enzymes. However, as the hydrogen-bonding groups in the ATP binding sites of these enzymes are fairly well-conserved, we have confirmed that inhibitor selectivity may be predominantly due to differences in either the hydrophobic or steric properties of their binding sites. In particular, the hydrophobic properties of regions outside the specificity surface were observed to provide a rationale for the differences in specificity between various inhibitors to these enzymes. Our method was thus able to identify variations in hydrophobicity. The greater hydrophobicity of certain regions of CDK4 over analogous regions in CDK2 was detectable; likewise, it was possible to distinguish variations in hydrophobicity for regions of CDK2 against those in ERK2, despite the fact that these regions are largely composed of similar residue types.

Surface composition and surface energy of Teflon treated by metal plasma immersion ion implantation

Plasma immersion ion implantation using a metal vacuum vapor arc (MEVVA) or cathodic arc source was used to modify the fluorine-based polymer, Teflon. Several transition metal ions such as Co, Ni, Cu were introduced into plasma and implanted into the Teflon surface. The chemical composition of the modified surface was determined by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The metals were found to be distributed several nanometers from the surface and XPS results showed the formation of metallic carbides and fluorides on the surface. Contact angle measurement results demonstrate the favorable change in the wettability from being hydrophobic to hydrophilic. Our study shows that the increase of the surface energy is due to the change of the surface interaction properties after metal plasma implantation.

The prediction of stiction failures in MEMS

The surface interaction energy of sticking surfaces has been the subject of considerable modeling and can be experimentally investigated. Much less is currently known about the influence that a certain surface interaction energy (distribution) has on the reliability of MEMS devices. The only treatises to date are purely black box statistical methods. In this paper, we discuss a comprehensive model that describes many stiction failure situations. For the first time, the surface interaction properties are linked directly to a reliability function.

Photon Probing of Solid State Materials

There is a need to develop cheaper catalytic materials with improved surface interaction properties. These materials are important for the creation of energy and the utilization of energy products (for example, coal gasification and auto exhaust purification). A new technique for determining the structure of catalysts and relationships between catalytic atoms and reactive species is presented. The techniques involve the Fourier analysis of extended X-ray absorption fine structures (EXAFS) with necessary supporting measurements such as EPR, LEED, etc. Examples of data from EXAFS and EPR measurements are given and catalytic relationships discussed.