Intrinsic Material Properties Research Articles

A steered molecular dynamics investigation on the role of glycation on the energy dissipation capacity of osteopontin at mineral interfaces in bone.

Type-2 Diabetes (T2D) is associated with a 3-fold increase in bone fracture risk. T2D impairs bone quality, whereby the intrinsic material properties of the bone matrix are altered, through glycation of collagenous and non-collagenous proteins (NCPs). There is a distinct lack of understanding of how altered protein configurations impair whole-bone biomechanics, particularly in the case of NCPs since their structural roles in bone are only now emerging. In this study, the effect of glycation on the energy dissipation behaviour of OPN, the most abundant NCP, on HydroxyApatite (HAp) mineral surfaces was investigated. The adsorption modes of OPN on the surface was obtained by conventional MD by comparing the residues residence time for each protein orientation with their average values. Then, energy dissipation of OPN was obtained through Steered Molecular Dynamics (SMD) by pulling simulations perpendicular to the surface. Two different glycation possibilities were considered whereby (a) Glycation occurred prior to Adsorption (GA) or (b) Adsorption took place before Glycation (AG). The simulation results showed that AG has the same adsorption modes as the healthy OPN, while the GA experienced a different mode. It was found that energy dissipation in absence of glycation was EOPN = 2646 kcal/mol. For glycated groups energy dissipation values were EOPN-AG = 2324 kcal/mol and EOPN-GA = 773 kcal/mol. The simulation results showed that OPN had reduced capacity for energy dissipation for either glycation case. However, it was notable that if OPN glycation occurred before its adsorption on HAp, its energy dissipation capacity was greatly reduced, which was caused by changes to the adsorption mode itself. The current study for the first time showed that the glycation sequence could negatively affects energy dissipation behaviour of OPN, which could have consequence for bone toughness.

Characterization of the electrical properties of mammalian peripheral nerve laminae.

The intrinsic electrical material properties of the laminar components of the mammalian peripheral nerve bundle are important parameters necessary for the accurate simulation of the electrical interaction between nerve fibers and neural interfaces. Improvements in the accuracy of these parameters improve the realism of the simulation and enables realistic screening of novel devices used for extracellular recording and stimulation of mammalian peripheral nerves. This work aims to characterize these properties for mammalian peripheral nerves to build upon the resistive parameter set established by Weerasuriya et al. in 1984 for amphibian somatic peripheral nerves (frog sciatic nerve) that is currently used ubiquitously in the in-silico peripheral nerve modeling community. A custom designed characterization chamber was implemented and used to measure the radial and longitudinal impedance between 10 mHz and 50 kHz of freshly excised canine vagus nerves using four-point impedance spectroscopy. The impedance spectra were parametrically fitted to an equivalent circuit model to decompose and estimate the components of the various laminae. Histological sections of the electrically characterized nerves were then made to quantify the geometry and laminae thicknesses of the perineurium and epineurium. These measured values were then used to calculate the estimated intrinsic electrical properties, resistivity and permittivity, from the decomposed resistances and reactances. Finally, the estimated intrinsic electrical properties were used in a finite element method (FEM) model of the nerve characterization setup to evaluate the realism of the model. The geometric measurements were as follows: nerve bundle (1.6 ± 0.6 mm), major nerve fascicle diameter (1.3 ± 0.23 mm), and perineurium thickness (13.8 ± 2.1 μm). The longitudinal resistivity of the endoneurium was estimated to be 0.97 ± 0.05 Ωm. The relative permittivity and resistivity of the perineurium were estimated to be 2018 ± 391 and 3.75 kΩm ± 981 Ωm, respectively. The relative permittivity and resistivity of the epineurium were found to be 9.4 × 106 ± 8.2 × 106 and 55.0 ± 24.4 Ωm, respectively. The root mean squared (RMS) error of the experimentally obtained values when used in the equivalent circuit model to determine goodness of fit against the measured impedance spectra was found to be 13.0 ± 10.7 Ω, 2.4° ± 1.3°. The corner frequency of the perineurium and epineurium were found to be 2.6 ± 1.0 kHz and 368.5 ± 761.9 Hz, respectively. A comparison between the FEM model in-silico impedance experiment against the ex-vivo methods had a RMS error of 159.0 ± 95.4 Ω, 20.7° ± 9.8°. Although the resistive values measured in the mammalian nerve are similar to those of the amphibian model, the relative permittivity of the laminae bring new information about the reactance and the corner frequency (frequency at peak reactance) of the peripheral nerve. The measured and estimated corner frequency are well within the range of most bioelectric signals, and are important to take into account when modeling the nerve and neural interfaces.

Optical modeling of single and multilayer two-dimensional materials and heterostructures

Bidimensional materials are ideally viewed as having no thickness, as their name suggests. Their optical response have been previously modelled by a purely bidimensional surface current or by a very thin film with some contradictory results. The advent of multilayer stacks of bidimensional materials and combinations of different materials in vertical van der Waals heterostructures highlights, however, that these materials have a finite thickness. In this article, we propose a new model that reconciles both approaches and we show how volume properties of stacked bidimensional layers can be calculated from the bidimensional response of each individual layer, and conversely. In our approach, each bidimensional layers is surrounded by vacuum and described as a kind of transfer matrix with intrinsic parameters that do not depend on the external medium. This provides a link between continuous thin films and discrete layers. We show how to model heterostructures of bidimensional materials and identify the parameters of the current sheet that represents the bidimensional material in the zero-thickness limit, namely the in-plane surface susceptibility and the out-of-plane displacement susceptibility. We show that our unified model is perfectly compatible with existing ellipsometric data with the same reliability as the existing interface model but with different values of the surface susceptibility or bulk dielectric function. We discuss in detail the origin of the discrepancies and show that our approach allows to determine intrinsic properties of the bidimensional materials with the advantage that multilayer and monolayer systems are described in a same framework.

Curvature sensing as an emergent property of multiscale assembly of septins

The ability of cells to sense and communicate their shape is central to many of their functions. Much is known about how cells generate complex shapes, yet how they sense and respond to geometric cues remains poorly understood. Septins are GTP-binding proteins that localize to sites of micrometer-scale membrane curvature. Assembly of septins is a multistep and multiscale process, but it is unknown how these discrete steps lead to curvature sensing. Here, we experimentally examine the time-dependent binding of septins at different curvatures and septin bulk concentrations. These experiments unexpectedly indicated that septins' curvature preference is not absolute but rather is sensitive to the combinations of membrane curvatures present in a reaction, suggesting that there is competition between different curvatures for septin binding. To understand the physical underpinning of this result, we developed a kinetic model that connects septins' self-assembly and curvature-sensing properties. Our experimental and modeling results are consistent with curvature-sensitive assembly being driven by cooperative associations of septin oligomers in solution with the bound septins. When combined, the work indicates that septin curvature sensing is an emergent property of the multistep, multiscale assembly of membrane-bound septins. As a result, curvature preference is not absolute and can be modulated by changing the physicochemical and geometric parameters involved in septin assembly, including bulk concentration, and the available membrane curvatures. While much geometry-sensitive assembly in biology is thought to be guided by intrinsic material properties of molecules, this is an important example of how curvature sensing can arise from multiscale assembly of polymers.

Influences of notch width and notch-tip angle on the fracture toughness measurement using the semi-circular bend (SCB) specimen

Semi-circular bend (SCB) method has been proposed by the International Society for Rock Mechanics and Rock Engineering (ISRM) as one of the four suggested methods for measuring the mode I fracture toughness of rocks. Due to limitations in the machining precision and the quasi-brittle nature of rocks, there exists inevitable measurement error in the measurement results using this method. Our previous study concluded that the SCB specimen with a sharp notch-tip (sharp-SCB) is the optimal configuration for minimizing the measurement error. This study further investigates the effects of notch width and notch-tip angle on the fracture toughness measurement using the sharp-SCB specimens. Five tip angles (i.e., 30°, 60°, 90°, 120°, and 150°) and three notch widths (i.e., 1 mm, 2 mm, and 3 mm) are considered. Within the theoretical framework of K-resistance (KR) curve, the results indicate that the initial load, peak load, critical crack length, and initial fracture toughness are all significantly dependent on the notch width and the notch-tip angle. As the intrinsic property of the rock material, the unstable fracture toughness is however relatively insensitive to these geometrical parameters. The error analysis of the experimental results shows that the ISRM suggested SCB method is reliable within certain ranges of these geometrical parameters. This study provides useful guidance on applying the ISRM suggested SCB method for quantifying rock fracture toughness.

Investigation into a practical approach and application of cotton fiber elongation

BackgroundThe strength of cotton fiber has been extensively studied and significantly improved through selective breeding, but fiber elongation has largely been ignored, even though elongation contributes to determining the energy needed to break fibers. Recent developments to calibrate the high volume instrument (HVI) for elongation has renewed interest in elongation. However, it is not understood how best to utilize yet another fiber property which has the potential to add to the complexity of fiber selection. To explore a practical approach to applying elongation, cotton samples were tested using single fiber methods, the Stelometer, and the HVI. Comparison of strength, elongation, and combined properties such as modulus were explored.ResultsHVI testing was shown to be sensitive enough to characterize elongation differences but unlike single fiber testing it was unable to capture within-sample variation. Fiber bundle testing, like Stelometer and HVI was shown to reduce bias due to fiber selection.ConclusionThe use of secant modulus, an intrinsic material property, allowed for one value to represent both strength and elongation. Secant modulus was shown to contain more useful information than either elongation or work-to-break. Work-to-break was shown to be more influenced by a specific value of breaking force or elongation rather than the intrinsic behavior of the sample being tested. Exploring the influence of genetics and environment on elongation, and its interaction with other fiber properties, requires additional work. Secant modulus, by combining strength and elongation into one value, shows the potential to incorporate elongation values into fiber characterization without increasing the complexity of current fiber selection processes.

Multi-source data-driven unsaturated seepage parameter inversion: Application to a high core rockfill dam

The inverse parameter’s estimation of unsaturated seepage models is important to ensure the safety of earth dams, while most existing studies determine the hydraulic characteristics only based on seepage pressure monitoring data, which may lead to inversion results deviating from the intrinsic properties of dam materials. This study proposed an advanced methodology for unsaturated seepage parameter inversion of earth dams driven by multi-source data. The transient unsaturated seepage behavior of earth dams is simulated using the Van Genuchten (VG) model, and the extreme learning machine (ELM) is adopted as the surrogate model to estimate the approximate simulation results. Then the multi-objective function for parameter inversion is constructed by combining the observed transient pressure data and ELM models, and the Pareto-optimal solutions are generated using the elitist non-dominated sorting genetic algorithm (NSGA-II). Multi-source information, including parameter design values, in-situ testing results, and monitoring data, are fused to construct a comprehensive index to drive the parameter decision. The proposed method is applied to the PB core rockfill dam, which has a well-established seepage pressure monitoring system. In addition, the design values and in-situ testing results of the hydraulic conductivity of the dam material are also available. The results showed that the inversion parameters of the proposed method are closer to the physical characteristics of materials and have advantages in prediction accuracy.

Thermal treated amidoxime modified polymer of intrinsic microporosity (AOPIM-1) membranes for high permselectivity reverse osmosis desalination

Despite the commercial success of polyamide reverse osmosis (RO) membranes for desalination, shortcomings of the material intrinsic properties hinder the further improvement of RO membrane permselectivity towards more energy-efficient desalination. Exploring new polymer materials is thus important to overcome the limitation of existing RO membrane materials. This work reports an investigation on an amidoxime modified polymer of intrinsic microporosity (AOPIM-1) as a membrane material for reverse osmosis desalination. AOPIM-1 is casted into a defect-free dense membrane, and followed by a thermal treatment to finetune its structural feature for enhanced salt rejection. As a polymer with stiff and distorted backbone structure, thermal treated AOPIM-1 possesses a high free volume and highly connected 0.3–0.8 nm micropores that provide fast water transport routes while regulating the permeation of ions. The rapid transport through the microporous channels gives the AOPIM-1 membrane a water permeability of 1.92 × 10−7 m·kg/m2·h·bar with NaCl rejection as high as 98.5 %. The thickness-normalized water permeability of AOPIM-1 membrane exhibits order-of-magnitude improvement comparing to conventional polyamide-based desalination membranes, and the permselectivity of the membrane is also found to be on the high side. This study confirms the possibility of utilizing microporous polymers as reverse osmosis membrane materials for high performance desalination.

Tailored Solvation and Interface Structures by Tetrahydrofuran-Derived Electrolyte Facilitates Ultralow Temperature Lithium Metal Battery Operations.

Ineffectiveness of Li-ion batteries (LIBs) in cold climates hinders electronics to work in various conditions including frigid environments, despite high demands. Given that intrinsic properties of LIB materials cause this problem, optimized cell chemistries ultimately are required for low-temperature usage. In this study, Li-metal batteries (LMBs) composed of a Li-metal anode (LMA) stabilized by a localized high-concentration electrolyte (LHCE) are found to significantly enhance low-temperature performance. The LHCE allows the LMA to have compact and regular deposition and excellent plating/stripping efficiency at sub-zero temperatures. The LHCE produces an inorganic-rich solid-electrolyte interphase with larger amounts of Li2 O/LiF interfaces, dominance of ion aggregates in Li+ solvation, and enhanced Li+ transport, which can greatly improve the LMA stability. LMB full cells based on LiNi0.8 Co0.1 Mn0.1 O2 cathodes with the tailored electrolyte show high retentions of 75 and 64 % at -20 and -40 °C, respectively. Furthermore, the LMB configuration retains its charge-discharge capability even at -60 °C.

Regulating the electronic structure of manganese-based materials to optimize the performance of zinc-ion batteries

The optimization of electronic structure is a common internal mechanism of all modification methods and acts as a general modification strategy for the intrinsic properties of manganese-based materials in zinc-ion batteries.

Multiscale modelling potentialities for solid oxide fuel cell performance and degradation analysis

Based on a multiscale approach, the in-home built Fortran code SIMFC allows for high-temperature fuel cell simulation from material intrinsic properties to system overall operation.

Voltage control of magnetic properties in GdxFe100-x films by hydrogen migration

Voltage control of magnetic properties is a promising path to realize low-power spintronic devices and meets the requirements for quicker information processing speed and ongoing scale reduction. Hydrogen migration induced by voltage gating has been demonstrated to modify the intrinsic magnetic properties of materials by affecting the exchange interaction, electron occupancy, and magnetoelastic effect. Herein, the magnetic properties of a ferrimagnetic Gd29Fe71 film in an all-solid-state multilayer device, which is constructed using a GdOx electrolyte, can be reversibly modulated by voltage-controlled hydrogen migration. Polar MOKE results indicate that hydrogen intercalation/deintercalation can modulate the Gd29Fe71 film's degree of compensation and control the dominant magnetic sublattice. Furthermore, the polarity of the polar MOKE curves can be reversibly switched. As with the increase in hydrogen loading, the compensation point in the Gd29Fe71 film is approached, the density of magnetic domain nucleation sites decreases, and the magnetic domain structures transform from labyrinth domains to uniform large area domains. At the same time, a strong perpendicular magnetic anisotropy is developed. This work shows a possible pathway for reversible control of magnetism in spintronic devices.

Single "Swiss-roll" microelectrode elucidates the critical role of iron substitution in conversion-type oxides.

Advancing the lithium-ion battery technology requires the understanding of electrochemical processes in electrode materials with high resolution, accuracy, and sensitivity. However, most techniques today are limited by their inability to separate the complex signals from slurry-coated composite electrodes. Here, we use a three-dimensional "Swiss-roll" microtubular electrode that is incorporated into a micrometer-sized lithium battery. This on-chip platform combines various in situ characterization techniques and precisely probes the intrinsic electrochemical properties of each active material due to the removal of unnecessary binders and additives. As an example, it helps elucidate the critical role of Fe substitution in a conversion-type NiO electrode by monitoring the evolution of Fe2O3 and solid electrolyte interphase layer. The markedly enhanced electrode performances are therefore explained. Our approach exposes a hitherto unexplored route to tracking the phase, morphology, and electrochemical evolution of electrodes in real time, allowing us to reveal information that is not accessible with bulk-level characterization techniques.

Assessing the structural and morphological effect on the tribological characteristics of boehmite and alumina sub-microparticles

Materials based on aluminium oxide can be obtained in different crystalline structures, making them suitable for several industrial applications. Chemical stability and high wear resistance are interesting peculiarities when materials undergo severe mechanical and thermal solicitations, like in breaking events, where aluminium oxides are indeed widely employed like abrasives. Controlled particles size and morphology can affect materials intrinsic properties, then representing a chance when fine adjustments in terms of specific features are required. With this in mind, we obtained boehmite and alumina sub-microparticles with different structural and morphological features by changing the synthesis parameters. The tribological properties where then investigated, using steel as counterface in pin on disc configuration. Both families can be classified as abrasive materials, but friction behaviour appears significantly different. Bohemite samples display high and stable friction coefficient, arising from a stable tribolayer formation, apart when gibbsite presence is observed, since iron hydroxide formed on the steel counterface dramatically reduces the friction stability. The behaviour of alumina family appears strongly driven by structural features, although particles shape change during the sliding tests also affects the COF value and stability.

Smart superamphiphobic surface manipulating wetting behaviors of oil droplet in water

Under limited lubrication oil supply, wettability is closely related to the distribution of oil around the contact zone, which directly affects lubricating performance of mechanical surfaces. Up to now, manipulating oil wetting behaviors remains a challenge. Here superamphiphobic surfaces are prepared by grafting perfluoroalkyl chain on superhydrophobic Cu coating without any low-surface-energy modifier. Furthermore, the surface chemistry of the superamphiphobic surfaces is finely adjusted by introducing terminal carboxyl group. Under the appropriate surface energy, superoleophilicity and superoleophobicity of the superamphiphobic surface in water can be efficiently switched via simply adjusting water pH value. Utilization of intrinsic wetting properties of materials will provide a pathway to guide programmable friction characteristics of engineering materials with controllable oil wetting behaviors in multiphase media.

Delayed Light‐Driven Actuations after Light Stopping

AbstractThe manipulation of light actuators benefits from the advantages of the immediacy of light response. However, the immediacy of light response leads to indispensability of light irradiation in the actuating processes. The actuation after light irradiation stops, i.e., a delayed actuation can execute actuation functions, which is free of direct light irradiation. Here are proposed several delayed actuation systems after light irradiation based on intrinsic delay properties of shape memory alloy materials and additional regulation of soft silicone layers. Continuous motions after light stopping have been realized such as linear and rotating motions. Moreover, the delayed actuation relatively separates the irradiation and actuation, where an operational window period is allowed for task execution in light‐preventing scenarios. The delay principle of light actuation overcomes the limitation of immediate response of light manipulation, and is also applicable to more materials and systems.

Rapid synthesis of MoS2–Ag nanocomposites via photoreduction for optical tuning and surface-enhanced Raman scattering applications

Semiconductor–metal nanocomposites have been widely investigated to modify the intrinsic properties of materials used for optoelectronic devices and sensing applications. In this study, a method for rapid synthesis of MoS2–Ag nanocomposites via laser-assisted photoreduction was proposed. For the photoreduction process, we used AgNO3 solution as a metal source. Under laser irradiation, Ag ions were easily reduced on MoS2 by photo-generated electrons from MoS2. The optical properties of MoS2–Ag nanocomposites were easily controlled by simple adjustment of the photoreduction time. To investigate the surface-enhanced Raman scattering (SERS) effect of the MoS2–Ag nanocomposites, the SERS spectra of methylene blue (MB) on MoS2–Ag nanocomposites were measured, and the nanocomposites were found to enhance the Raman scattering intensity of MB up to ∼106. Therefore, the laser-assisted photoreduction method has great potential for rapid synthesis and optical tuning of semiconductor–metal nanocomposites.

Neural network based iterative learning control for magnetic shape memory alloy actuator with iteration-dependent uncertainties

The magnetic shape memory alloy based actuator (MSMA-BA) is an indispensable component mechanism for high-precision positioning systems as it possesses the advantages of high precision, low energy consumption, and large stroke. However, hysteresis is an intrinsic property of MSMA material, which seriously affects the positioning accuracy of MSMA-BA. In this study, we propose a multi meta-model approach incorporating the nonlinear auto-regressive moving average with exogenous inputs (NARMAX) and Bouc–Wen (BW) models to describe the complex dynamic hysteresis of MSMA-BA. In particular, the BW model is introduced into the NARMAX model as an exogenous variable function, and a wavelet neural network (WNN) is adopted to construct the nonlinear function of the multi meta-model. In addition, iterative learning control is combined with a WNN to improve its convergence speed. A two-valued function is employed in the controller design process, so as to make use of history iteration information in updating control input. The main contribution of this study is the convergence analysis of the proposed iteration learning controller with iteration-dependent uncertainties (non-strict repetition of the initial state and varying iteration length). The experiments conducted on the MSMA-BA illustrate the validity of the proposed control scheme.

High‐Performance Monolayer MoS2 Field‐Effect Transistors on Cyclic Olefin Copolymer‐Passivated SiO2 Gate Dielectric

AbstractTrap states of the semiconductor/gate dielectric interface give rise to a pronounced subthreshold behavior in field‐effect transistors (FETs) diminishing and masking intrinsic properties of 2D materials. To reduce the well‐known detrimental effect of SiO2 surface traps, this work spin‐coated an ultrathin (≈5 nm) cyclic olefin copolymer (COC) layer onto the oxide and this hydrophobic layer acts as a surface passivator. The chemical resistance of COC allows to fabricate monolayer MoS2 FETs on SiO2 by standard cleanroom processes. This way, the interface trap density is lowered and stabilized almost fivefold, to around 5 × 1011 cm−2 eV−1, which enables low‐voltage FETs even on 300 nm thick SiO2. In addition to this superior electrical performance, the photoresponsivity of the MoS2 devices on passivated oxide is also enhanced by four orders of magnitude compared to nonpassivated MoS2 FETs. Under these conditions, negative photoconductivity and a photoresponsivity of 3 × 107 A W−1 is observed which is a new highest value for MoS2. These findings indicate that the ultrathin COC passivation of the gate dielectric enables to probe exciting properties of the atomically thin 2D semiconductor, rather than interface trap dominated effects.

Unravelling the Interfacial Dynamics of Bandgap Funneling in Bismuth-Based Halide Perovskites.

An environmentally friendly mixed-halide perovskite MA3 Bi2 Cl9- x Ix with a bandgap funnel structure has been developed. However, the dynamic interfacial interactions of bandgap funneling in MA3 Bi2 Cl9- x Ix perovskites in the photoelectrochemical (PEC) system remain ambiguous. In light of this, single- and mixed-halide lead-free bismuth-based hybrid perovskites-MA3 Bi2 Cl9- y Iy and MA3 Bi2 I9 (named MBCl-I and MBI)-in the presence and absence of the bandgap funnel structure, respectively, are prepared. Using temperature-dependent transient photoluminescence and electrochemical voltammetric techniques, the photophysical and (photo)electrochemical phenomena of solid-solid and solid-liquid interfaces for MBCl-I and MBI halide perovskites are therefore confirmed. Concerning the mixed-halide hybrid perovskites MBCl-I with a bandgap funnel structure, stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions results in more efficient exciton transport. Besides, MBCl-I's effective diffusion coefficient and electron-transfer rate demonstrate efficient heterogeneous charge transfer at the solid-liquid interface, generating improved photoelectrochemical hydrogen production. Consequently, this combination of photophysical and electrochemical techniques opens up an avenue to explore the intrinsic and interfacial properties of semiconductor materials for elucidating the correlation between material characterization and device performance.