Surface Stress Changes Research Articles

(Invited) Reaction-Based Microcantilever Sensors

Microcantilevers (MCLs) have emerged as a cost-effective, label-free, and portable analytical technique for detecting chemical and biological species. The method offers notable advantages, particularly its high sensitivity, enabling the precise detection of cantilever motion at sub-nanometer levels. Furthermore, MCLs can be effectively fabricated into a multi-element sensor array, amplifying their capabilities. While many sensors rely on adsorption-induced frequency or surface stress changes of MCLs, there is a notable gap in the literature. Despite numerous review articles on MCLs, none have specifically focused on summarizing these sensors with an emphasis on reactions. Beyond their role in detecting chemical species, MCLs present a distinctive application in characterizing the morphology and mechanical properties of materials at solid-liquid or solid-gas interfaces during reaction processes. I will discuss the reaction based MCL sensors and also their potential applications in monitoring reactions.

Time-Series Analysis of Mining-Induced Subsidence in the Arid Region of Mongolia Based on SBAS-InSAR

Mongolia’s substantial mineral resources have played a pivotal role in its economic progress, with mining activities significantly contributing to this development. However, these continuous mining operations, particularly at the Oyu Tolgoi copper and gold mine, have induced land subsidence that threatens both production activities and poses risks of geological and other natural disasters. This study employs the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technique to monitor and analyze time-series surface subsidence using 120 Sentinel-1A datasets from 2018 to 2022. The findings reveal that the SBAS-InSAR method successfully captures the subsidence and its spatial distribution at Oyu Tolgoi, with the maximum cumulative subsidence reaching −742.01 mm and the highest annual average subsidence rate at −158.11 mm/year. Key drivers identified for the subsidence include variations in groundwater levels, active mining operations, and changes in surface stress. This research underscores the ongoing subsidence issue at the Oyu Tolgoi mining area, providing crucial insights that could aid in enhancing mining safety and environmental conservation in the region.

The Force-Frequency Characteristics of Quartz Wafers under a Cantilever Beam Structure.

This study investigated the force-frequency characteristics of quartz wafers inside a cantilever beam frame. Firstly, the force-frequency coefficient formula of quartz wafers with fixed ends under axial force was analyzed. Firstly, the formula for the force-frequency coefficient of quartz wafers with fixed ends under axial force was analyzed. A force-frequency coefficient formula suitable for cantilever beam structures was derived by considering the changes in surface stress and stiffness of quartz wafers with fixed ends and one end under force on the other. Subsequently, the formula's accuracy was verified by experiments, and the accuracy was more than 92%. In addition, strain simulation analysis was performed on three different shapes of quartz wafers, and experimental verification was carried out on two of them. The results revealed that trapezoidal quartz wafers and cantilever beam structures exhibited superior stress distribution to rectangular chips. Furthermore, by positioning electrodes at various locations on the surface of the quartz chip, it was observed that, as the electrodes moved closer to the fixed end, the force-frequency coefficient of the rectangular quartz chip increased, along with an increase in chip strain under the cantilever structure. In summary, this study provides a new approach for designing cantilever quartz resonator sensors in the future.

The Role of Bottom Friction in Mediating the Response of the Weddell Gyre Circulation to Changes in Surface Stress and Buoyancy Fluxes

Abstract The Weddell Gyre is one of the dominant features of the Southern Ocean circulation and its dynamics have been linked to processes of climatic relevance. Variability in the strength of the gyre’s horizontal transport has been linked to heat transport toward the Antarctic margins and changes in the properties and rates of export of bottom waters from the Weddell Sea region to the abyssal global ocean. However, the precise physical mechanisms that force variability in the Weddell’s lateral circulation across different time scales remain unknown. In this study, we use a barotropic vorticity budget from a mesoscale eddy active model simulation to attribute changes in gyre strength to variability in possible driving processes. We find that the Weddell Gyre’s circulation is sensitive to bottom friction associated with the overflowing dense waters at its western boundary. In particular, an increase in the production of dense waters at the southwestern continental shelf strengthens the bottom flow at the gyre’s western boundary, yet this drives a weakening of the depth-integrated barotropic circulation via increased bottom friction. Strengthening surface winds initially accelerate the gyre, but within a few years the response reverses once dense water production and export increases. These results reveal that the gyre can weaken in response to stronger surface winds, putting into question the traditional assumption of a direct relationship between surface stress and gyre strength in regions where overflowing dense water forms part of the depth-integrated flow.

The Effect of Surface Oil on Ocean Wind Stress

This study provides, to the best of our knowledge, the first detailed analysis of how surface oil modifies air–sea interactions in a two-way coupled model, i.e., the coupled–ocean–atmosphere–wave–sediment–transport (COAWST) model, modified to account for oil-related changes in air–sea fluxes. This study investigates the effects of oil on surface roughness, surface wind, surface and near-surface temperature differences, and boundary-layer stability and how those conditions ultimately affect surface stress. We first conducted twin-coupled modeling simulations with and without the influence of oil over the Deepwater Horizon (DWH) oil spill period (20 April to 5 May 2010) in the Gulf of Mexico. Then, we compared the results by using a modularized flux model with parameterizations selected to match those selected in the coupled model adapted to either ignore or account for different atmospheric/oceanic processes in calculating surface stress. When non-oil inputs to the bulk formula were treated as being unchanged by oil, the surface stress changes were always negative because of oil-related dampening of the surface roughness alone. However, the oil-related changes to 10 m wind speeds and boundary-layer stability were found to play a dominant role in surface stress changes relative to those due to the oil-related surface roughness changes, highlighting that most of the changes in surface stress were due to oil-related changes in wind speed and boundary-layer stability. Finally, the oil-related changes in surface stress due to the combined oil-related changes in surface roughness, surface wind, and boundary-layer stability were not large enough to have a major impact on the surface current and surface oil transport, indicating that the feedback from the surface oil to the surface oil movement itself is insignificant in forecasting surface oil transport unless the fractional oil coverage is much larger than the value found in this study.

Study of surface morphology in GaAs by hydrogen and helium implantation at elevated temperature

In this work, the surface morphology and internal defect evolution process of GaAs substrates implanted with light ions of different fluence combinations are studied. The influence of H and He ions implantation on the atomic mechanism of the blister phenomenon observed after annealing is investigated. Raman spectroscopy is used to measure the surface stress change of different samples before and after implantation and annealing. Optical microscopy and atomic force microscopy are used to characterize the morphology changes of the GaAs surface under different annealing conditions. The evolution of bubbles and defects in GaAs crystals is revealed by transmission electron microscopy. Through this study, it is hoped that ion implantation fluence, surface exfoliation efficiency and exfoliation cost can be optimized. At the same time, it also lays a foundation for the heterointegration of GaAs film on Si.

Compressive Stress and Charge Redistribution during CO Adsorption Onto Pt

Electroorganic reactions, where energy is either stored or released from chemical bonds within carbon-based molecules, are essential to help achieve a circular carbon-based economy. Central to electrochemical conversion of organic molecules is carbon monoxide (CO), which serves as both an intermediate in electrochemical CO2 reduction to hydrocarbons and electrochemical oxidation in fuel cells that operate via oxygenated hydrocarbons (e.g., ethanol, methanol). For the latter, Pt has been the predominate catalyst of choice, and substantial effort has been spent to identify the mechanistic details for complete oxidation of alcohol-based fuels. With CO conversion serving as an important if not rate-limiting step of the oxidative process, it is critical to understand the state of a catalytic surface when CO is present.The change in surface stress associated with the adsorption and oxidative stripping of CO on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte.1 The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO free and CO-saturated electrolyte. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage, and within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers account for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of materials platforms for sensing and catalysis. References D. Raciti, K.A. Schwarz, J. Vinson, and G.R. Stafford, The Journal of Physical Chemistry C , 126, 4446-4457 (2022).

Modelling anisotropic adsorption-induced coal swelling and stress-dependent anisotropic permeability

To investigate the anisotropy of coal swelling, this study proposes an effective stress model for saturated, adsorptive fractured porous media by considering gas adsorption induced surface stress change on solid-fluid interface. The effective stress model can be used to capture the anisotropic swelling of coal combining anisotropic mechanical properties and to link with the anisotropic permeability. Direction dependent fracture compressibility is used to describe the evolution of anisotropic stress-dependent permeability behaviour. Particularly, the impact of gas adsorption on fracture compressibility is considered in the model. The proposed models were tested against experimental results and compared to relevant existing models available in literatures. The model predicts that the coal swelling in the direction perpendicular to the bedding plane, is greater than that in the parallel plane. Coal permeability in each direction can be affected by the stress changes in any directions. The permeability parallel to the bedding plane is more sensitive to change in stresses than in perpendicular to the bedding due to higher fracture compressibility. The cleat compressibility could increase with gas adsorption, especially for carbon dioxide. Permeability loss in the direction parallel to the bedding plane is more significant than that in the direction perpendicular to the bedding plane. The presented models provide a tool for quantifying gas adsorption-induced anisotropic coal swelling and permeability behaviours.

Compressive Stress and Charge Redistribution during CO Adsorption onto Pt.

The change in surface stress associated with the adsorption and oxidative stripping of carbon monoxide (CO) on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte. The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO-free and CO-saturated electrolytes. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage and, within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO-bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers accounts for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of material platforms for sensing and catalysis.

Analytical calculation method for passive tensile damage of asphalt concrete waterproof sealing structure of ballastless track subgrade

The theoretical development of the temperature effect of the full-section asphalt concrete waterproof sealing structure (ACWSS) of the ballastless track subgrade lags the engineering practice. In order to reveal the passive tensile damage behavior of ACWSS from the perspective of theoretical analysis, in this paper, the base plate of the ballastless track and the ACWSS is simplified into an elastic–viscoelastic double layer composite beam model. The analytical calculation method for passive tensile damage of ACWSS under temperature load is derived theoretically. The change of surface stress and strain of ACWSS with time is calculated and analyzed. The theoretical analysis and calculation results show that the variation of the surface strain, the maximum strain, and the time corresponding to the strain peak of ACWSS are consistent with the measured results. The model of the double-layer composite beam has high reliability, and the analytical calculation method of passive tensile damage is reasonable and practical. The temperature stress of ACWSS at the expansion joint of the base plate is synchronized with the temperature change, indicating that the asphalt concrete at this location is mainly subjected to axial tension (or compression). It is suggested that the structural design should be judged by comparing the number of periodic temperature loads and the allowable fatigue number of asphalt concrete, which further improves the design method and technical system of the ACWSS in China's high-speed railway. It has important theoretical and practical significance.

Numerical research on the dynamic rock-breaking process of impact drilling with multi-nozzle water jets

Based on the arbitrary Lagrangian-Eulerian finite element method (ALE-FEM), a coupling model for simulating the rock mass destruction process under the impact of a high-pressure water jet was established. Through the analysis of multi-nozzle jets’ impact on rock surface stress changes, the process of rock breaking and pore formation, and the rock breaking dynamic damage evolution, the mechanism of rock breaking by multi-nozzle jets was revealed by analyzing the stress distribution and dynamic damage of the rock mass during the impact process. The results show that nozzle jets with different inclination angles exhibit different rock breaking methods, which are mainly tensile failure and radial shear fracturing caused by the impact of the water jets. Rock breaking using multi-nozzle jets can be divided into four stages: the elastic deformation stage, the plastic deformation stage, the micro-fracture stage, and the complete failure stage. Based on the spatial-temporal evolution of the damage, the damage depth and scope of rock mass caused by multi-nozzle jets with different tilt angles are different. The results of this study provide a theoretical basis for the effect and optimization of the impact of multi-nozzle jets on rock breaking.

Atomic mixed-mode cohesive-zone dual constitutive laws of impurity-embrittled grain boundaries in polycrystalline solids via nanoscale field projection method

Atomic-scale mixed-mode intergranular fracture, featured by non-local non-linear discrete atomic debonding processes near a crack tip along a grain boundary (GB), is modeled with a cohesive zone in a continuum scale controlled by cohesive-zone dual constitutive relations, a balanced traction-separation relationship, i.e., a conventional cohesive-zone law (CZL), and an unbalanced traction (UT)-centerline displacement (CD) relationship. In order to bridge two different scales, we developed a nanoscale field projection method (nano-FPM) based on atomic-scale interaction J and M integrals, for which asymptotic anisotropic elastic fields near an interfacial crack with balanced and unbalanced crack-face tractions are used as probing fields of the CZL and UT-CD relationship, respectively. Cracking phenomena along a GB in nickel with segregated sulfur impurity atoms under mixed-mode loadings are simulated with molecular dynamics. Embrittlement by sulfur impurity atoms is quantitatively estimated with the mixed-mode CZL of the GBs in nickel via the nano-FPM developed in this study. UT-CD relationship, a special feature of atomic fracture, representing the micromechanical change of surface stress between GB and cracked surfaces, is also obtained by the nano-FPM. New functional relationships for CZL, UT-CD relationship, and decohesion potential obtained by the nano-FPM are proposed to facilitate the implementation of them into mesoscale or continuum-scale analysis on mixed-mode intergranular fracture.

Hemodynamic effects of intracranial aneurysms from stent-induced straightening of parent vessels by stent-assisted coiling embolization.

Straightening of parent vessels happens for stent-assisted coiling embolization (SACE) treatment of intracranial aneurysms. This study aims to investigate aneurysmal hemodynamic modifications caused by stent-induced vessel straightening. Stent and coil deployments of a SACE-treated distal bifurcation aneurysm by finite element method were performed first with the preoperative (not straightened, NS) and postoperative (straightened, S) vessel models respectively. Computational fluid dynamics were then performed for eight models, including (I) NS only model, (II) NS+stent model, (III) NS+coils model, (IV) NS+stent+coils model, (V) S only model, (VI) S+stent model, (VII) S+coils model, and (VIII) S+stent+coils model. Finally, changes in aneurysmal flow velocity, isovelocity surface and wall shear stress (WSS) were analyzed qualitatively and quantitatively. The flow was less in the S models than that in the corresponding NS models. Coils blocked most of the flow into the aneurysm sac in both NS models and S models and vessel straightening had more profound effect on the high aneurysmal flow volume reduction than coiling, while stenting generated adverse effect on flow reduction. Taking the NS only model as baseline (100%), the sac-averaged velocities of models II to VIII were 112%, 36%, 42%, 45%, 39%, 12%, 13%, and high flow volumes were 119%, 21%, 30%, 10%, 8%, 3%, 3%, while the sac-averaged WSSs were 106%, 37%, 44%, 41%, 35%, 17% and 24%, respectively. Stent-induced vessel straightening combined coil embolization has the best performance in hemodynamic modifications and may reduce the recurrence rate, whereas stenting may generate adverse effect on hemodynamic alterations.

Portable Real-Time Detection of Pb(II) Using a CMOS MEMS-Based Nanomechanical Sensing Array Modified with PEDOT:PSS.

Detecting the concentration of Pb2+ ions is important for monitoring the quality of water due to it can become a health threat as being in certain level. In this study, we report a nanomechanical Pb2+ sensor by employing the complementary metal-oxide-semiconductor microelectromechanical system (CMOS MEMS)-based piezoresistive microcantilevers coated with PEDOT:PSS sensing layers. Upon reaction with Pb2+, the PEDOT:PSS layer was oxidized which induced the surface stress change resulted in a subsequent bending of the microcantilever with the signal response of relative resistance change. This sensing platform has the advantages of being mass-produced, miniaturized, and portable. The sensor exhibited its sensitivity to Pb2+ concentrations in a linear range of 0.01–1000 ppm, and the limit of detection was 5 ppb. Moreover, the sensor showed the specificity to Pb2+, required a small sample volume and was easy to operate. Therefore, the proposed analytical method described here may be a sensitive, cost-effective and portable sensing tool for on-site water quality measurement and pollution detection.

Label-free attomolar protein detection using a MEMS optical interferometric surface-stress immunosensor with a freestanding PMMA/parylene-C nanosheet

We demonstrated an optical interferometer-based surface-stress immunosensor using freestanding polymethyl methacrylate (PMMA)/parylene-C nanosheet with high sensitivity for detection of biomolecules. PMMA/parylene-C nanosheets were transferred onto a silicon substrate with microcavities to fabricate freestanding submicron-thick membrane with a sealed cavity structure. The adhesive force between the transferred parylene-C and binder parylene-C layer was measured to be 1.06–2.4 N/10 mm by tape test. Evading Debye shielding, these nanomechanical sensors allow detection of the adsorption on the membrane surface through changes in surface stress transduced by the electric charge. We optimized the density of receptors and mode of immobilization for high sensitivity. To evaluate the selectivity of the sensor, membrane deflections induced by various proteins were measured and the spectral shifts showed high selectivity only for the target antigen. The minimum limit of detection (LOD) of the sensor for human serum albumin antigen was 0.1–1 fg/mL (1.5–15 aM), which was 20,000 times lower than that of the conventional micro-cantilever sensor.

The effect of Biot coefficient and elastic moduli stress–pore pressure dependency on poroelastic response to fluid injection: laboratory experiments and geomechanical modeling

AbstractBiot coefficient and elastic moduli are typically assumed to have a constant value for analyzing poroelastic effects of fluid injection. To investigate the stress–pore pressure dependency of Biot coefficient and elastic moduli, we conducted a series of laboratory experiments on a porous dolomite core sample from a reef in Michigan basin. We varied the confining stress as well as the pore pressure in the experiments. Then, modeling was performed using analytical poroelastic solutions and a coupled two‐phase flow‐geomechanical numerical simulation (for CO2 injection). The modeling results show that the variability of Biot coefficient and elastic moduli should be included in the geomechanical modeling to accurately predict the poroelastic responses of injection (i.e., stress changes and surface uplift). Using a constant stress‐independent Biot coefficient elastic moduli, which is the assumption in poroelastic modeling, leads to underestimation of the stress change and surface uplift due to injection compared to a realistic stress–pore pressure dependent Biot coefficient, which is updated at each time step of injection modeling. Modeling results indicate that decreasing elastic modulus combined with Biot coefficient increase due to the fluid injection could lead to a larger surface uplift and stress changes in the reservoir. In addition, the stress changes and uplift due to injection are a function of initial in situ stress due to Biot coefficient and elastic modulus stress–pore pressure dependency. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Multiscale Modeling Reveals the Cause of Surface Stress Change on Microcantilevers Due to Alkanethiol SAM Adsorption.

Experimental results show that the adsorption of the self-assembled monolayers (SAMs) on a gold surface induces surface stress change that causes deformation of the underlying substrate. However, the exact mechanism of stress development is yet to be elucidated. In the present study, multiscale computational models based on molecular dynamics (MD) simulations are applied to study the mechanism governing surface stress change. Distinct mechanisms for adsorption-induced surface deformation, namely, interchain repulsion and thiol-gold interaction-driven gold surface reconstruction, are investigated. Two different interatomic potentials, embedded atom method and surface-embedded atom method (SEAM), are used in the MD simulations to study the reconstruction-induced surface stresses. Comparison of the predicted surface stress changes, resulting from MD and continuum mechanics-based models, with the observed experimental response indicates that a modified SEAM-based multiscale model can better capture the surface stress changes observed during alkanethiol SAM formation, and gold surface reconstruction is the primary factor behind the surface stress change. The interchain repulsions of SAM are found to have a minimal contribution. Also, both the simulations and experiments show that the surface stress change increases with the increase of surface coverage density and larger grain size.

Long-term deformations of monopile foundations for offshore wind turbines studied with a high-cycle accumulation model

A parametric study on the long-term deformations of monopile foundations for offshore wind turbines is presented. The finite element calculations of a monopile in fine sand were performed with a high-cycle accumulation (HCA) model. The results are analyzed with respect to the horizontal displacements, the tilting of the pile head, settlement of the ground surface and effective stress changes in the surrounding soil. The dimensions of the pile (diameter, length of embedding, wall thickness), the initial density of the sand and the cyclic loading (average value, amplitude, lever arm) have been varied. The influence of the drainage conditions (either fully drained or partially drained) is also discussed. The validity of Miner’s rule is checked for both types of drainage conditions. Furthermore, the effect of changes of the direction of the cycles and of a multidimensional cyclic loading is addressed. The interesting phenomenon of a “self-healing”, i.e. a re-erection of the deformed monopile after a storm event, is demonstrated based on simulations with small cycles following a large preloading. Simulations with homogeneous and stochastically fluctuating fields of void ratio are compared.

Stress Estimation Using the Acoustoelastic Effect of Surface Waves in Weak Anisotropic Materials

This paper proposes a novel stress measurement method using the acoustoelastic effect of surface wave to estimate the stress of a homogeneous material plate with orthogonal anisotropy, in which the surface wave velocities are measured in three different directions before and after loading stress. The effectiveness of the proposed method was verified by numerical simulations and experiments. For the simulations, the surface wave velocities in three directions were obtained from a conventional perturbation model for weak anisotropic materials. The simulation results showed that the stress estimation error was less than 3% for an anisotropic rate up to 2% under stress conditions up to 90 MPa. Two specimens were prepared for the experiments, one was almost isotropic and another that had a relatively larger anisotropy rate of 2.6%. Then, the stresses loaded by a tensile test machine were estimated. The results showed good agreement with the given stresses for both specimens. These results confirm that the proposed method can be applied to estimate the surface stress state in anisotropic material plates. The proposed method is simple, practical, and is expected to be useful for monitoring changes of surface stress before and after machining such as the punching or bending of plate.

Microcantilever aptasensor for detecting epithelial tumor marker Mucin 1 and diagnosing human breast carcinoma MCF-7 cells

In this paper, a simple and novel method based on microcantilever for detecting tumor biomarker MUC1 and diagnosing human breast carcinoma MCF-7 cells was proposed. With thiolated aptamers of MUC1 self-assembled on the sensing microcantilever, the targets interact with aptamers resulting in the change of surface stress on the microcantilever. As a result, MUC1 and MCF-7 cells were successfully detected. Among them, the differential deflection of the microcantilever is linear with the logarithm of the MUC1 concentration in the range of 5–500 nM with low detection limit of 0.9 nM. However, for MCF-7 cells, the linear relationship between cantilever deflection and cell concentration ranges from 2.0*103 to 5.4*104 cells/mL with low detection limits of 213 cells/mL. In the meantime, according to the characteristics of real-time recording the change of microcantilever deflection over time, we have speculated the dynamic process of the binding of MUC1 to the aptamers. This work has confirmed that the aforementioned microcantilever aptasensor could sensitively detect other biomarkers and provide dynamic information of binding, and also could be used to identify tumor cells.