Effect Of Interfacial Stress Research Articles

Microfluidic Stress Device to Decouple the Synergistic Effect of Shear and Interfaces on Antibody Aggregation

Protein denaturation and aggregation resulting from the effects of interfacial stress, often enhanced by flow and shear stress, pose significant challenges in the production of therapeutic proteins and monoclonal antibodies. The influence of flow on protein stability is closely intertwined with interfacial effects. In this study, we have developed a microfluidic device capable of exposing low volume (< 320 µL) protein solutions to highly uniform shear. To disentangle the synergistic impact of flow and interfaces on protein aggregation, we fabricated two devices composed of different materials, namely poly(methyl methacrylate) (PMMA) and stainless steel. Upon application of shear, we observed formation of protein particles in the micron-size range. Notably, The number of particles generated in the steel devices was ∼ 3.5 fold lower than in the PMMA device, hinting at an interface-mediated effect. With increasing the protein concentration from 1 to 50 mg/mL we observed a saturation in the amount of aggregates, further confirming the key role of solid-liquid interfaces in inducing particle formation. Introduction of non-ionic surfactants prevented protein aggregation, even at the highest tested protein concentration and low surfactant concentrations of 0.05 mg/mL. Overall, our findings corroborate the synergistic impact of shear and interface effects on protein aggregation. The device developed in this study offers a small-scale platform for assessing the stability of antibody formulations throughout various stages of the development and manufacturing process.

Effect of interfacial stress on microchemistry and coercivity in 2:17-type SmCo sintered magnets

The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu element within the cell boundary phase, and the gradient of Cu distribution increases with aging time, together with coercivity. However, the fundamental origin of such Cu gradient distribution is not clear. In this work, the element redistribution and interfacial stress change during the aging process were simultaneously analyzed by employing typical Sm(CobalFe0.16Cu0.08Zr0.03)7.6 magnets with and without slow cooling. The increased atomic diffusion after slow cooling leads to a narrow width and large Cu distribution gradient of 1:5H phase, contributing to a high coercivity. Meanwhile, the lattice mismatch at the 1:5H/2:17R interface along 〈1¯010〉2:17R direction was enhanced in the magnet with slow cooling, giving rise to a large interfacial stress. Such interfacial stress was found, via physical chemistry analysis, to contribute to the gradient of Cu distribution in the 1:5H phase. The combined analysis of transmission electron microscopy, geometric phase analyses, and micromagnetic simulations reveal the presence of the interfacial stress together with a large concentration and gradient of Cu distribution in the 1:5H phase can improve the coercivity. These findings provide new considerations for the design of high-performance 2:17-type SmCo magnets.

The effect of carbon nanotube electrodes on electron transport properties of nanowire phase change material Ge[formula omitted]Sb[formula omitted]Te[formula omitted]

The present work studied the scalability of phase change material (PCM) down to a single-digit nm with single wall metallic carbon nanotubes (SWCNT) electrodes. For this purpose, the low bias electron transport properties of Ge2Sb2Te5 (GST) are investigated using a DFT–NEGF formalism. The amorphous Ge2Sb2Te5 (a-GST) is obtained using DFT-based molecular dynamic simulation. It has been seen that while 6 nm crystalline Ge2Sb2Te5 (c-GST) has a large transmission near the Fermi level, a-GST exhibits a clear band-gap, and by further reduction of its length to 12 Å, the band-gap disappears. The electrical conductance of nanowire a-GST is predominantly due to coherent electron transport via acceptor-like and donor-like traps. The c-GST/a-GST conductance (Gc/Ga) ratio as a function of the device length is calculated, which shows good agreement compared with experimental works. We show that the ultimate limit for downscaling the nanowire GST sandwiched between SWCNT electrodes is about 24 Å . This can be attributed to the overlapping metal-induced gap states from electrodes that lead to the disappearance of the band-gap of the amorphous phase and a sharp decrease in the Gc/Ga ratio in shorter channel length. The On/Off ratio of 12 Å GST sharply drops below 10, and the reliable read procedure is not possible on this size scale. We have also investigated the effect of interfacial stress between the electrode and GST and show that it reduces the Gc/Ga ratio and hurts the switch-ability of the device.

Interfacial Stress‐Modulated Mechanosensitive Upconversion Luminescence of NaErF4 Based Heteroepitaxial Core–Shell Nanoparticles

AbstractThe resulting interfacial stress in heteroepitaxial nanocomplex usually has negligible influence on its performance, but at high pressures (HP) the effect can be significantly amplified. In order to unravel the underlying mechanism and search for high quality pressure sensors, a simple object is employed, NaErF4@NaLnF4 (Ln = Y, Lu, Gd) and its Tm3+‐doped derivatives, to comparatively study the effect of interfacial stress on upconversion (UC) luminescence. Specifically, the doping enhances greatly mechanosensitivity because of the anisotropic local geometry of the dopant ions of which the structural distortion is amplified by HP. The generated compressive strain does extend into the core as witnessed by the effect of tensile strain in the shell on the core and the fact that Lu‐shelled nanoparticles are the most sensitive to external force among Tm3+‐doped system. This compressive strain in concert with the external HP intensifies the coupling between Er3+ and Tm3+, making the attenuation of green UC emission more pronounced. The red to green UC emission ratio of this material, robust both in structural and optical properties, increases linearly with pressure in the range from ambient to 9 GPa. The study opens a new horizon for understanding the effect of interfacial stress on UC luminescence.

Modifying energy storage performances of new lead-free system ferroelectric capacitors through interfacial stress

Ferroelectric energy storing is one of the most potential research hotspots in functional materials. To seek for better performance, current strategies are mostly relied on structure designing and multi-element (more than 5) doping. Till now, energy storage density (ESD) for ferroelectric thin film capacitors have reached to over 100 J/cm3, which seems to be a bottleneck, and the corresponding material structure and chemical composition are also becoming complex. Thus, exploiting simple and single-layered candidates will probably re-develop this field. For epitaxial thin films, interfacial stress from substrates will assist. Hence, a new system of Sm doped BaZr0.2Ti0.8O3 (BaZr0.2Ti0.8O3-2%Sm2O3, abbr. BZTS) thin films were epitaxially grown on STO substrates and a better ESD of 40.42 J/cm3 with η of 85.03% was obtained in 200-nm film. The effects of interfacial stress between films and substrates on the ferroelectric performance of BZTS thin films have been systematically discussed. The interfacial pressure stress offered by substrates enhanced the thermal stability and Sm doping facilitated the ferroelectric behavior. Finally, this new BZTS system thin films shown rather a better ferroelectric reliability in both temperature and frequency than the only-BZT system, making it a proper candidate to be composited with other materials in next-generation functional materials.

Influence of Interfacial Stress on Microstructural Evolution in NiAl Alloys

A phase-field model for the phase transition between austenite and martensite and twinning between two martensitic variants is presented from our previous theory [1] with the main focus on the influence of interfacial stress that is consistent with the sharp interface limit. Each variant-variant transformation can be represented by only one order parameter. Thus, it allows us to get the analytical solution of interface energy and width. Coupled phase-field and elasticity equations are solved for cubic-to-tetragonal phase transformation in NiAl shape memory alloy. The effects of interfacial stress are studied for martensite-martensite interfaces in detail, which was absent in [1]. Additionally, stress and temperature-induced growth of the martensitic phase inside austenite and twining are simulated. Some of the nontrivial experimentally observed microstructures reproduced in the simulations [1] are analyzed in detail. It includes tip splitting and bending, and twins crossing. This theory can be extended for electric, reconstructive, and magnetic phase transformations.

Effects of interfacial stress in phase field approach for martensitic phase transformation in NiAl shape memory alloys

A phase field approach for phase transition between austenite to martensitic variants and twinning between martensitic variants is presented with the main focus on the effects of interfacial stress on phase transformations. In this theory, each variant-variant phase transformations and twinnings within each martensitic variant can be represented by only one-order parameter. Thus, it allows us to get the analytical solution of the martensite-martensite interface profile, energy, and width. Moreover, this model allows us to include interface stress which is consistent with the sharp interface limit. The finite element method is utilized to solve the coupled phase field and elasticity equations for a cubic to tetragonal phase transformation in NiAl shape memory alloy. The stress fields are obtained and the effects of interfacial stress on the stress field at the interfaces are studied for both austenite–martensite and martensite–martensite interfaces in detail. Additionally, the temperature-induced growth of the martensitic phase inside austenite, martensitic phase transformation, and twining are solved. The evolution of the microstructure and stress fields are obtained and the effects of interfacial stress on the morphological evolution of martensitic nanostructures are examined. It is found that the interfacial stress is an important factor, influencing the stress distribution at interfaces and the phase field solution significantly. This theory can be extended for electric, reconstructive, and magnetic phase transformations.

ANALYTICAL SOLUTION FOR POROUS-FLUID FLOW CHARACTERISTICS WITH STRESS JUMP INTERFACIAL CONDITION

The complicated mass and momentum transfer problems in the porous region,especially at the interface between porous and free fluid region were analyzed in an asymmetric and coupled porous-fluid channel. By taking the Brinkman-extended Darcy model in the porous region with the velocity continuity and the shear stress jump interface conditions, the fluid transfer characteristics were solved. The analytical expressions for the fluid flow velocity of each region and friction coefficient in the coupled asymmetric channel were proposed by considering the stress jump interfacial condition. Then the effects of interfacial stress jump coefficient, Darcy number and dimensionless off-center thickness of porous layer on fluid flow velocity and friction coefficient were studied. The results show that under certain conditions changing the interface property can obviously control the velocity profile in each region of the coupled channel. For certain values of Darcy number and porous off-center thickness, increasing the interfacial stress coefficient has a reducing effect on the interfacial velocity but an increasing effect on the fluid friction coefficient, and the effect is more obvious when the interfacial stress coefficient is less than 0, in this case that without considering the effect of the interfacial stress coefficient can cause larger error. When both the interfacial stress coefficient and the porous off-center thickness are smaller negative values, the effect by varying the porous off-center thickness on the interfacial velocity is greater than the effect of altering the interfacial stress coefficient, while when the interfacial stress coefficient and the porous off-center thickness of porous layer are larger positive values, the result is quite the opposite. At a larger Darcy number, both the interfacial stress coefficient and porous off-center thickness have greater influence on the fluid friction coefficient; reducing Darcy number to a certain small value, the influence of interfacial stress coefficient on fluid friction coefficient can be neglected and the fluid friction coefficient is only related to the porous off-center thickness, and much more sensitive to a larger porous off-center thickness.

Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure.

FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized.

Combined voids size and shape effects on the macroscopic criterion of ductile nanoporous materials

In this paper, we investigate the interfacial stress effects on the macroscopic yield function of ductile porous media containing nanosized spheroidal cavities. The solid matrix is assumed rigid-ideal plastic and of von Mises type with associated flow rule. We then perform limit analysis of a spheroidal unit cell containing a confocal spheroidal (prolate or oblate) cavity and subjected to arbitrary mechanical loadings. Voids size effects are captured by considering at the interface between the matrix and the cavity a surface stress model which relates the jump of the traction vector to the interfacial residual stress and interfacial plastic strain. This accounts for a thin shell of material in which occurs a strong plastic strain accumulation. We then provide a closed-form two-field based estimate of the overall dissipation which contains additional terms related to the interfacial plasticity. By taking advantage of this result, we derive parametric equations of the macroscopic yield surface of the nanoporous plastic material. The obtained estimates are assessed through comparisons with numerical data. Finally, it is shown that the resulting macroscopic criterion of the nanoporous material exhibits specific features such as (i) a dependence of the yield stress on the size of the spheroidal nanovoids, (ii) asymmetry between the yield stress in uniaxial tension and compression, (iii) more pronounced size effects for oblate voids than for prolate ones.

Semi-analytical investigation of stress interfacial effects in ductile media with nanosized spheroidal cavities

In this paper we investigate the interfacial stress effects on the macroscopic yield strength of plastic porous media containing nanosized spheroidal cavities. The solid matrix is assumed to obey the von Mises criterion with associated flow rule. Analysis of a rigid-ideal plastic spheroidal unit cell, containing a confocal spheroidal cavity, and subjected to arbitrary mechanical loadings is made. Void size effects are captured by considering at the interface between the matrix and the cavity a surface stress model, which relates the jump of the traction vector to the interfacial residual stress and to interfacial plastic strain. The resulting macroscopic criterion for the nanoporous material exhibits unusual features such as (i) an increase of the yield stress when the void size is decreased, (ii) asymmetry between the yield stress in uniaxial tension and compression.

Hyperelastic large deformations of two-phase composites with membrane-type interface

The composite under investigation consists of two phases which are bonded together through a membrane-type interface. The work reported in this paper aims at studying the hyperelastic large deformations of this composite while accounting for interfacial stress effects. A variational formulation for a general traction boundary value problem of the composite is provided, leading to the local bulk and interfacial equilibrium equations and to the traction boundary conditions. Assuming that each bulk phase is incompressible and characterized by an energy density function depending only on the trace of the right Cauchy–Green bulk strain tensor and that the interface is compressible and defined by an energy density function being isotropic with respect to the right Cauchy–Green surface strain tensor, exact solutions are given for the simple axial extension, simple torsion and out-of-plane shear of a fiber-reinforced cylinder, and a closed-form solution is also found for a hollow composite sphere subjected both to an internal pressure and an external pressure. These analytical results are further specified and discussed in the particular case where each bulk phase is described by an incompressible Neo–Hookean law and the interface is specified by a compressible Neo–Hookean law. Apart from their own usefulness, the results obtained in this work can serve as benchmarks for relevant numerical methods.

Combination of short‐range periodicity and interfacial stress effects on valence band scheme in strained MQW (GaN/AlGaN)n

AbstractWe observed intense photoluminescence from the GaN well layers of the multi‐quantum well consisting of GaN and Al0.24Ga0.76N with various thicknesses (about 0.8, 1.6, 2.4 nm) of the GaN well layers. The peak position of the photoluminescence largely shifts towards the higher energy and the peak intensity becomes strong enormously with the decreasing of the GaN well‐layer thickness. We qualitatively discuss on the effects of the interfacial stress (strain) and the induced dielectric polarization in addition to the short‐range periodicity to elucidate the observed phenomena instead of the usual explanation based on an internal electric field effect, that seems to be too intuitive and of little physical logic. The band scheme alteration is also discussed with the observed phenomena of the photoluminescence in connection with the above argument. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Effect of the Interfacial Stress Distribution on the Material Interfacial Shear Strength Measurement

An integrated experimental and numerical analysis is carried out to study the interfacial shear strength of bonded materials. Two types of shear tests, namely the Iosipescu shear test, and the short-beam shear test are employed to understand the effect of interfacial stress on the interfacial shear strength measurements. The measured average shear strengths are very close, even though the interfacial shear stress distributions of these two kinds of specimens are very different. Therefore, we conclude that the interfacial stress distribution has the least effect on the interfacial strength measurement if the interfacial shear stress is non-singular.

Size-dependent effective dynamic properties of unidirectional nanocomposites with interface energy effects

This article studies the size effect on wave propagation characteristics of plane longitudinal and transverse elastic waves in a two-phase nanocomposite consisting of transversely isotropic and unidirectionally oriented identical cylindrical nanofibers embedded in a transversely isotropic homogeneous matrix. The surface elasticity theory is employed to incorporate the interfacial stress effects. The effect of random distribution of nanofibers in the composite medium is taken into account via a generalized self-consistent multiple scattering model. The phase velocities and attenuations of longitudinal and shear waves along with the associated dynamic effective elastic constants are calculated for a wide range of frequencies and fiber concentrations. The numerical results reveal that interface elasticity at nanometer length scales can significantly alter the overall dynamic mechanical properties of nanofiber-reinforced composites. Limiting cases are considered and excellent agreements with solutions available in the literature have been obtained.

Stress Dependence of Oxidation Reaction at SiO2/Si Interfaces during Silicon Thermal Oxidation

The microscopic processes of interfacial reaction of O2 molecules involving compressive stress normal to SiO2/Si(001) interface are investigated by first-principles total-energy calculations. It is found that the energy barrier height for the O2 reaction increases with residual stress at the interface. This is because the energy of the transition state structure for O2 diffusion before O2 insertion into the Si substrate is higher than that for the stress-free interface. The calculated activation volume (7.9 Å3) is comparable to those obtained by numerical simulations using experimental data, implying that the effects of interfacial stress on the reaction of O2 molecules play important roles during thermal oxidation of silicon nanostructures.

Elastic field of an isotropic matrix with a nanoscale elliptical inhomogeneity

In traditional continuum mechanics, the effect of surface energy is ignored as it is small compared to the bulk energy. For nanoscale materials and structures, however, the surface effects become significant due to the high surface/volume ratio. In this paper, two-dimensional elastic field of a nanoscale elliptical inhomogeneity embedded in an infinite matrix under arbitrary remote loading and a uniform eigenstrain in the inhomogeneity is investigated. The Gurtin–Murdoch surface/interface elasticity model is applied to take into account the surface/interface stress effects. By using the complex variable technique of Muskhelishvili, the analytic potential functions are obtained in the form of an infinite series. Selected numerical results are presented to study the size-dependency of the elastic field and the effects of surface elastic moduli and residual surface stress. It is found that the elastic field of an elliptic inhomogeneity under uniform eigenstrain is no longer uniform when the interfacial stress effects are taken into account.

Effect of interfacial stresses on the elastic behavior of nanocomposite materials

This work analyzes the effective bulk modulus of a composite material consisting of spherical inclusions at dilute concentrations. By introducing the theory of surface elasticity and accounting for the contribution of interfacial stresses, a closed-form expression for the effective bulk modulus is derived. The analysis shows that the dependence of the elastic response on the size of the embedded inclusions in the composite material is different from the classic results obtained in the theory of linear elasticity. This is because of shrinkage of the inclusions caused by the interfacial stresses. The interfacial stresses can either enhance or reduce the effective bulk modulus depending on the bulk modulus ratio of matrix to inclusion.

Novel interface-binding chloroperoxidase for interfacial epoxidation of styrene

A unique interface-binding chloroperoxidase (CPO) was developed and examined for interfacial biocatalysis. Native CPO was conjugated with polystyrene (PS) to form a surfactant-like structure that self assembled at oil–water interfaces. While enantioselectivity of the enzyme was maintained, the interfacial assembly of the enzyme improved its overall catalytic efficiency as compared to that observed with the enzyme contained in the bulk aqueous phase. The PS conjugated CPO (PS-CPO) showed a 2.5-fold enhancement of enzyme productivity versus native CPO under batch reaction conditions for the epoxidation of styrene, whereas a 25-fold improvement was realized in a continuous feeding reaction to reach a productivity of 10 μmol h −1 mg protein −1. The interface-binding enzyme also demonstrated several other advantages such as suppressing unwanted side reactions including the hydrolysis of styrene epoxide products, stabilizing the enzyme by limiting its exposure to both the oxidant H 2O 2 and epoxide products, and alleviating the deactivating effect of interfacial stress on enzymes by functioning as a surfactant.

Effect of interfacial stress on the crystalline structure of the matrix and the mechanical properties of high‐density polyethylene/CaCo3 blends

Effect of interfacial stress on the crystalline structure of the matrix and the mechanical properties of high‐density polyethylene/CaCo₃ blends