Influence Of Mechanical Strain Research Articles

The impact of mechanical strain on magnetic and structural properties of 2D materials: A Monte Carlo study.

The inherent flexibility of two-dimensional (2D) materials allows for efficient manipulation of their physical properties through strain application, which is essential for the development of advanced nanoscale devices. This study aimed to understand the impact of mechanical strain on the magnetic properties of two-dimensional (2D) materials using Monte Carlo simulations. The effects of several strain states on the magnetic properties were investigated using the Lennard-Jones potential and bond length-dependent exchange interactions. The key parameters analyzed include the Lindemann coefficient, radial distribution function, and magnetization in relation to temperature and magnetic field. The results indicate that applying biaxial tensile strain generally reduces the critical temperature (Tc). In contrast, the biaxial compressive strain increased Tc within the elastic range, but decreased at higher strain levels. Both compressive and tensile strains significantly influence the ferromagnetic properties and structural ordering, as evidenced by magnetization hysteresis. Notably, pure shear strain did not induce disorder, leaving the magnetization unaffected. In addition, our findings suggest the potential of domain-formation mechanisms. This study provides comprehensive insights into the influence of mechanical strain on the magnetic behavior and structural integrity of 2D materials, offering valuable guidance for future research and advanced material design applications.

Influence of circadian rhythm on effects induced by mechanical strain in periodontal ligament cells.

The aim of this study was to investigate the influence of mechanical strain on clock gene function in periodontal ligament (PDL) cells. Furthermore, we wanted to analyze whether effects induced by mechanical stress vary in relation to the circadian rhythm. Human PDL fibroblasts were synchronized in their circadian rhythm with dexamethasone and stretched over 24 h. Unstretched cells served as controls. Gene expression of the core clock genes were analyzed at 4 h intervals by quantitative real-time polymerase chain reaction (qRT-PCR). Time points 0 h (group SI1) and 12 h (group SI2) after synchronization served as starting points of a4 h force application period. Collagen-1α (COL-1α/Col-1α), interleukin-1β (IL1-β), and runt-related transcription factor 2 (RUNX2/Runx2) were assessed by qRT-PCR and enzyme-linked immunosorbent assay (ELISA) after 2 and 4 h. Statistical analysis comprised one-way analysis of variance (ANOVA) and posthoc tests. After synchronization, the typical pattern for clock genes was visible in control cells over the 24 h period. This pattern was significantly altered by mechanical strain. Under tensile stress, ARNTL gene expression was reduced, while Per1 and2 gene expression were upregulated. In addition, mechanical stress had adifferential effect on the expression of Col-1α and IL1‑β depending on its initiation within the circadian rhythm (group SI1 vs group SI2). For RUNX2, no significant differences in the two groups were observed. Our results suggest that mechanical stress affects the molecular peripheral oscillator of PDL cells. Vice versa, the circadian rhythm also seems to partially influence the effects that mechanical stress exerts on PDL cells.

The Influence of Mechanical Strains and Quantum-Size Effects on the Photosensitivity of Ge/Ge(x)Si(1-x) Nanofilm

Calculations of the maximum light wavelength of intrinsic absorption for the unstrained and strained germanium nanofilm were carried out. It was established that the photosensitivity of such nanofilm with the thickness of d 10 nm significantly depends on the effects of dimensional quantization and the magnitude of internal mechanical strains. It is shown that the variation of the thickness of the germanium nanofilm and the component composition of the Ge(x)Si(1–x) substrate allow controlling by its photosensitivity in the range from 0.8 to 4 μm.

Editorial: Strong field physics and attosecond science

emission from Rydberg atoms. Substantial neutral atoms can be excited after tunneling in a strong laser 14 field, in the process known as frustrated tunneling ionization. The generation of coherent emission from 15 the excited-state atoms produced by the frustrated tunneling ionization is demonstrated to be dependent on 16 the chirp of the laser pulse. This chirp dependence also provides a new way to investigate the dynamics 17 of Rydberg states. Kong et al. (Kong et al., 2022) explored the influence of mechanical strains on the 18 high-order harmonic generation in the monolayer hexagonal boron nitride crystal by using time-dependent 19 density functional theory. They found the band structure is sensitive to the structural deformation modulated 20 by strains. This result may be useful in probing lattice deformations in crystals and heuristic to enhance the 21 optoelectronic efficiency of solid-state nano-devices. In conclusion, the Research Topic is created to present the latest advances and trends concerning the 62 strong field physics and attosecond science. Our special thanks to the Frontiers in Physics team for the 63 technical assistance with publishing. Much more efforts are still ongoing in this fascinating area. We expect 64 that this field will attract more and more attentions and benefit potential applications.

Analysis of Mechanical Strain in AlGaN/GaN HFETs

Herein, the influence of mechanical strain induced by passivation layers on the electrical performance of AlGaN/GaN heterostructure field‐effect transistor is investigated. We studied the physical mechanism of a threshold voltage (Vth) shift for the monolithically fabricated on/off devices reported earlier by our group. For that, theoretical calculations, simulation‐based analysis, and nano‐beam electron diffraction (NBED) measurements based on STEM are used. Strain distribution in the gate vicinity of transistors is compared for a SiNx passivation layer with intrinsic stress from ≈0.5 to −1 GPa for normally on and normally off devices, respectively. The strain in epitaxial layers transferred by intrinsic stress of SiNx is quantitatively evaluated using NEBD method. Strain dissimilarity Δε = 0.23% is detected between normally on and normally off devices. Using this method, quantitative correlation between 1.13 V of Vth shift and microscopic strain difference in the epitaxial layers caused by 1.5 GPa intrinsic stress variation in passivation layer is provided. It is showed in this correlation that about half of the reported threshold voltage shift is induced by strain, i.e., by the piezoelectric effect. The rest of Vth shift is caused by the fabrication process. Therefore, various components/mechanisms contributing to the measured Vth shift are distinguished.

Strain effects on high-harmonic generation in monolayer hexagonal boron nitride

Based on the time-dependent density functional theory, we theoretically investigate the influence of mechanical strains on the high-order harmonic generation (HHG) in the monolayer hexagonal boron nitride (hBN) crystal. We show that mechanical strains can largely modify the band structure and facilitate the harmonic emission. Compared to uniaxial strains, we find that biaxial strains may enhance the HHG yield significantly, and the HHG spectroscopy generated by a linearly polarized laser is closely related to the symmetry of the deformed hBN. Moreover, when driven by a circularly polarized laser, we find that the appearance of the 3n-order harmonics manifests the restoration of the three-fold rotational symmetry. Our results will be useful in controlling the HHG spectroscopy and probing lattice deformations in crystals.

Absence of Walker Breakdown in the Dynamics of Chiral Néel Domain Walls Driven by In-Plane Strain Gradients

The influence of mechanical strain on the static and dynamic properties of chiral domain walls (DWs) in perpendicularly magnetized strips is investigated using micromagnetic simulations and a one-dimensional model. While a uniform strain allows one to reversibly switch the domain-wall configuration at rest between Bloch and N\'eel patterns, strain gradients are suggested as an energy-sustainable means to drive domain-wall motion without the need for magnetic fields or electrical currents. It is shown that an in-plane strain gradient creates a force on a domain wall that drives it towards a region of higher tensile (compressive) strain for materials with positive (negative) magnetostriction. Moreover, due to the dependence of the domain-wall internal energy on the in-plane strain, a damping torque proportional to the local strain arises during motion that opposes the precessional torque due to the driving force, which is proportional to the strain gradient. After a transient period, where both the internal DW angle and the velocity change nonmonotonically, reaching their maximum values asynchronously, the two torques balance each other. This compensation prevents the onset of turbulent domain-wall dynamics, and steady domain-wall motion with a constant velocity is asymptotically reached for an arbitrarily large strain gradient. Despite this complex dynamics, our work shows that average domain-wall velocities in the range of 500 m/s can be obtained using voltage-induced strain in piezoelectric/ferromagnetic devices under realistic conditions.

A method to analyze the influence of mechanical strain on dermal collagen morphologies

Collagen fibers and their orientation play a major role in the mechanical behavior of soft biological tissue such as skin. Here, we present a proof-of-principle study correlating mechanical properties with collagen fiber network morphologies. A dedicated multiphoton stretching device allows for mechanical deformations in combination with a simultaneous analysis of its collagen fiber network by second harmonic generation imaging (SHG). The recently introduced Fiber Image Network Evaluation (FINE) algorithm is used to obtain detailed information about the morphology with regard to fiber families in collagen network images. To demonstrate the potential of our method, we investigate an isotropic and an anisotropic ex-vivo dorsal pig skin sample under quasi-static cyclic stretching and relaxation sequences. Families of collagen fibers are found to form a partially aligned collagen network under strain. We find that the relative force uptake is accomplished in two steps. Firstly, fibers align within their fiber families and, secondly, fiber families orient in the direction of force. The maximum alignment of the collagen fiber network is found to be determined by the largest strain. Isotropic and anisotropic samples reveal a different micro structural behavior under repeated deformation leading to a similar force uptake after two stretching cycles. Our method correlates mechanical properties with morphologies in collagen fiber networks.

Comparison of Experimentally Determined Two-Dimensional Strain Fields and Mapped Ultrasonic Data Processed by Coda Wave Interferometry.

Due to the high sensitivity of coda waves to the smallest structural alterations such as strain, humidity or temperature changes, ultrasonic waves are a valid means to examine entire structures employing networks of ultrasonic transducers. In order to substantiate this ex ante assessment, the viability of measuring ultrasonic waves as a valid point of reference and inference for structural changes is to be further scrutinized in this work. In order to investigate the influence of mechanical strain on ultrasonic signals, a four-point bending test was carried out on a reinforced concrete beam at Ruhr University Bochum. Thus, measurements collected from a network of selected transducer pairings arranged across the central, shear-free segment of the test specimen, were correlated to their respective strain fields. Detected ultrasonic signals were evaluated employing Coda Wave Interferometry. Such analysis comprised the initial non-cracked state as well as later stages with incremental crack depth and quantity. It was to ascertain that the test specimen can in fact be qualitatively compartmentalized into areas of compression and tension identified via Relative Velocity Changes presented in Attribute Maps. However, since results did not entail a zero crossing, i.e., neither positive nor negative values were to be calculated, only relative changes in this work displayed staggered over the height of the object under test, are discussed. Under the given methodological premises, additional information is currently required to make quantitative assertions regarding this correlation of ultrasonic and strain results. This holds true for the comparability of the ultrasonic and strain results for both non-cracked and even the cracked state.

Massless Dirac fermions in stable two-dimensional carbon-arsenic monolayer

We predict from DFT based electronic structure calculations that a monolayer made up of Carbon and Arsenic atoms, with a chemical composition (CAs3) forms an energetically and dynamically stable system. The optimized geometry of the monolayer is slightly different from the buckled geometric configuration observed for silicene and germanene. The results of electronic structure calculations predict that it is a semi-metal. Interestingly, the electronic band structure of this material possesses a linear dispersion and a Dirac cone at the Fermi level around the high symmetric K point in the reciprocal lattice. Thus, at low energy excitation (up to 105 meV), the charge carriers in this system behave as massless Dirac-Fermions. Detailed analysis of partial density of state suggests that the 2pz orbital of C atoms plays vital role in determining the nature of the states, which has a linear dispersion and hence the Dirac cone, around the Fermi level. Thus, the electronic properties of CAs3 monolayer are similar to those of graphene and other group IV based monolayers. In addition, we have also investigated the influence of mechanical strain on the properties of CAs3 monolayer. The buckled configuration becomes the planar configuration for a tensile strain beyond 18%. Our results indicate that the monolayer possesses linear dispersion in the electronic band structure for a wide range of mechanical strain from -12 to 20%, though the position of Dirac point may not lie exactly at the Fermi level. The linear dispersion disappears for a compressive strain beyond -12% & it is due to the drastic changes in the geometrical environment around C atom. Finally, we wish to point out that CAs3 monolayer belongs to the class of Dirac materials where the behaviour of particles, at low energy excitations, are characterized by the Dirac-like Hamiltonian rather than the Schrodinger Hamiltonian.

Lithium chloride attenuates suppressed differentiation induced by mechanical strain in cementoblasts

ABSTRACTAim: The purpose of this study was to investigate the influence of mechanical strain on OCCM-30 cementoblast differentiation and Wnt/β-catenin pathway activity.Materials and Methods: Mechanical tension in the form of 2500-µ strain was applied to the cells using the Forcel four-point bending system, with or without the Wnt signaling activator, lithium chloride. Changes in cell differentiation and the expression of Wnt/β-catenin pathway components in response to strain and lithium chloride were assessed by real-time PCR, immunofluorescence, and western blotting.Results: The mRNA expression levels of the cementoblastogenesis-related genes alkaline phosphatase, runt-related transcription factor 2, and collagen 1, were decreased with mechanical strain. Similarly, the Wnt signaling pathway component genes LRP5, AXIN2, and LEF1 were decreased. The immunofluorescence assay demonstrated that scant β-catenin underwent nuclear translocation after the cells were subjected to mechanical strain. Moreover, western blotting showed that the protein levels of both β-catenin and phosphorylated β-catenin were increased after mechanical strain. In the presence of lithium chloride, the differentiation that was suppressed by mechanical strain was attenuated.Conclusions: 2500-µ strain mechanical strain inhibited cementoblast differentiation activity in vitro, which could be alleviated by actviating Wnt/β-catenin signaling using lithium chloride.

Impaired Wound Healing of Alveolar Lung Epithelial Cells in a Breathing Lung-On-A-Chip.

The lung alveolar region experiences remodeling during several acute and chronic lung diseases, as for instance idiopathic pulmonary fibrosis (IPF), a fatal disease, whose onset is correlated with repetitive microinjuries to the lung alveolar epithelium and abnormal alveolar wound repair. Although a high degree of mechanical stress (>20% linear strain) is thought to potentially induce IPF, the effect of lower, physiological levels of strain (5–12% linear strain) on IPF pathophysiology remains unknown. In this study, we examined the influence of mechanical strain on alveolar epithelial wound healing. For this purpose, we adopted the “organ-on-a-chip” approach, which provides the possibility of reproducing unique aspects of the in vivo cellular microenvironment, in particular its dynamic nature. Our results provide the first demonstration that a wound healing assay can be performed on a breathing lung-on-a-chip equipped with an ultra-thin elastic membrane. We cultured lung alveolar epithelial cells to confluence, the cells were starved for 24 h, and then wounded by scratching with a standard micropipette tip. Wound healing was assessed after 24 h under different concentrations of recombinant human hepatic growth factor (rhHGF) and the application of cyclic mechanical stretch. Physiological cyclic mechanical stretch (10% linear strain, 0.2 Hz) significantly impaired the alveolar epithelial wound healing process relative to culture in static conditions. This impairment could be partially ameliorated by administration of rhHGF. This proof-of-concept study provides a way to study of more complex interactions, such as a co-culture with fibroblasts, endothelial cells, or immune cells, as well as the study of wound healing at an air–liquid interface.

Unexpected field-induced dynamics in magnetostrictive microstructured elements under isotropic strain

We investigated the influence of an isotropic strain on the magnetization dynamics of microstructured magnetostrictive Co40Fe40B20 (CoFeB) elements with time-resolved scanning transmission x-ray microscopy. We observed that the application of isotropic strain leads to changes in the behavior of the microstructured magnetostrictive elements that cannot be fully explained by the volume magnetostriction term. Therefore, our results prompt for an alternative explanation to the current models used for the interpretation of the influence of mechanical strain on the dynamical processes of magnetostrictive materials.

Strain engineering of nonlinear boron phosphate for phase matching in the ultraviolet region: a first-principles study

Borophosphates, particularly BPO4 (BPO) crystals, have attracted attention in laser frequency conversion devices because of their short ultraviolet cutoff edge and relatively large second harmonic generation (SHG) response, which is almost twice as great as that of KH2PO4. However, the birefringence of BPO (approximately 0.005) is too small to satisfy the phase matching condition in the ultraviolet spectral region, restricting the laser output efficiency. Here we systematically examine the influence of mechanical strains on the atomic structure as well as the electronic and optical properties of BPO using first-principles calculations. Interestingly, we find that the birefringence of BPO can be enhanced by ~0.06 through external uniaxial strain along the c-axis. Meanwhile, compressive strain can increase the band gap and SHG coefficients effectively. Refractive-index dispersion is also emphasized in this work. Our results indicate that phase matching in the ultraviolet region (266 nm) can be achieved under −10% strain (3.9 GPa). This investigation is helpful for understanding the structure–property relationship of BPO under strain, and it also indicates its possible use as a promising ultraviolet nonlinear optical crystal.

Lithium Chemical Potential Change in Lithium Ion Battery Cathodes Under Mechanical Strain

In solid-state ionic devices, such as all-solid-state lithium ion batteries (LIBs) and solid oxide fuel cells (SOFCs), mechanical strain might be induced at the electrode/electrolyte hetrointerfaces during the cell fabrication process and the operation because of differences in the crystal structures and the chemical/thermal expansion coefficients. Such mechanical strain at the heterointerfaces might affect thermodynamic and kinetic properties of the electrodes and the electrolyte, resulting in deterioration or improvement of the devices’ performance. In this work, we investigated the influence of mechanical strain on lithium chemical potential in cathode materials for LIBs. Dense thin film electrodes, such as LiCoO2 and LiFePO4, were fabricated on a solid-state lithium ion conductor, such as Li0.29La0.57TiO3 (LLT) and Li7La3Zr2O12 (LLZ). The change in the lithium chemical potential in the electrode was evaluated by measuring electromotive force (EMF) between the electrode under compressively- or tensely-strained condition and one under stress-free condition. A clear EMF was generated when a mechanical strain was applied to the electrode. Typically, a positive and negative EMF was observed for a compressive and tensile stress, respectively. When the mechanical strain was released, EMF returned to zero. EMF seemed to increase proportionally with increasing the amount of mechanical strain. Such an EMF accompanied with the mechanical strain was discussed from thermodynamic points of view and, as results, could be related to the lithium partial molar volume of the electrode material.

Piezoresistivity of thin film semiconductors with application to thin film silicon solar cells

The influence of mechanical strain on the conductivity (piezoresistivity) of intrinsic and doped hydrogenated amorphous and microcrystalline silicon (a-Si:H and μ-Si:H) thin films as well as indium tin oxide and aluminum doped zinc oxide is examined under uniaxial tension and compression. The aim of this work is to characterize and model the influence of stress on thin film solar cells. The resistivity of intrinsic a-Si:H and μ-Si:H as well as that of n-type a-Si:H and μ-Si:H decreases with increasing tensile strain whereas it is increasing for both p-type materials. Both ITO and ZnO:Al show no significant change in resistivity with tensile strain until a critical strain value of roughly 0.5% that initiates fracture and introduces a non-reversible resistivity increase. Such irreversible changes occur for silicon layers at higher strains (1%). Silicon nitride buffer layers decrease the value of this critical strain. Tensile tests inside a scanning electron microscope demonstrate that such irreversible changes are related to crack formation when a certain tensile strain is exceeded. Analytical and numerical calculations are performed to estimate the influence of strain on the efficiency of p-i-n solar cells, which is roughly +/−0.3% for a biaxial strain of +/−1%.

Regulation of YAP by Mechanical Strain through Jnk and Hippo Signaling

Mechanical forces affect all the tissues of our bodies. Experiments conducted mainly on cultured cells have establishedthat altering these forces influences cell behaviors, including migration, differentiation, apoptosis, and proliferation [1, 2]. The transcriptional coactivator YAP has been identified as a nuclear relay of mechanical signals, but the molecular mechanisms that lead to YAP activation were not identified [3]. YAP is the main transcriptional effector of the Hippo signaling pathway, a major growth regulatory pathway within metazoa [4], but at least in some instances, the influence of mechanical strain on YAP was reported to be independent of Hippo signaling [5, 6]. Here, we identify a molecular pathway that can promote the proliferation ofcultured mammary epithelial cells in response to cyclic orstatic stretch. These mechanical stimuli are associated with increased activity of the transcriptional coactivator YAP, which is due at least in part to inhibition of Hippo pathway activity. Much of this influence on Hippo signaling can be accounted for by the activation of c-Jun N-terminal kinase (JNK) activity by mechanical strain and subsequent inhibition of Hippo signaling by JNK. LATS1 is a key negative regulator of YAP within the Hippo pathway, and we further show that cyclic stretch is associated with a JNK-dependent increase in binding of a LATS inhibitor, LIMD1, to the LATS1 kinase and that reduction of LIMD1 expression suppresses the activation of YAP by cyclic stretch. Together, these observations establish a pathway for mechanical regulation of cell proliferation via JNK-mediated inhibition of Hippo signaling.

Mechanically robust, ITO-free, 4.8% efficient, all-solution processed organic solar cells on flexible PET foil

We present all-solution processed, indium tin oxide-free organic solar cells on mechanically flexible polyethylene terephthalate (PET) substrates with power conversion efficiencies up to 4.8%. The mechanical properties of the devices are dictated by the electrodes from either metal-organic silver inks or a combination of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) and silver nanowires. Both electrodes can sustain high tensile strains. The influence of mechanical strain on the solar cell performance was experimentally studied in situ by measuring the J–V curves of elongated samples under illumination. At a strain of 14%, we still observed 90% of the initial device power output. At higher strain, crack formation within the electrodes was identified as the origin for device failure.

Cyclic stretch increases the expression of fibronectin through cPLA2, STAT3, and Akt phosphorylation in renal tubular epithelial cells (690.18)

Extracellular matrix accumulation contributes to the progression of chronic renal disease. Recent in vivo data indicate that unilateral ureteral obstruction (UUO), a model for chronic obstructive nephropathy, induces profibrotic renal tubular cell injury via STAT3 activation. A characterization of obstructive nephropathy and UUO is an increase in intrarenal pressure resulting in tubular mechanical stretch. However, in the kidney, the influence of mechanical strain on renal tubular epithelial (RTE) cells remains unclear. It is possible that tubular mechanical strain may attribute to increased STAT3 activation leading to accumulation of the extracellular matrix protein, fibronectin, in RTE cells. Human proximal tubular HK‐2 cells were either or not subjected to cyclic mechanical stretch on a uniform biaxial strain device. Fibronectin expression increased significantly in response to cyclic stretch, which was attenuated by inhibition of cPLA2, but not sPLA2 or iPLA2. In addition, treatment of cells with arachidonic acid resulted in an increased expression of fibronectin. Cyclic stretch also stimulated phosphorylation of STAT3 and Akt, and inhibition of STAT3, Akt, or its upstream activator phosphatidyl inositol 3‐kinase (PI3‐K), attenuated stretch‐induced fibronectin accumulation. Expression of dominant negative Akt or transfection of small interfering RNA targeting STAT3 significantly blocked stretch‐induced increase in fibronectin, indicating a role for these kinases in fibronectin accumulation. Taken together, these results provide the first evidence for a role of cPLA2, STAT3, and Akt in stretch‐induced fibronectin expression in RTE cells.

Influence of strain on space-charge distribution at ferroelectric thin-film free surfaces

Ferroelectric perovskites are wide-bandgap semiconductors and therefore are often modeled as perfect dielectrics. However, space charges can play an important role in regions with large electric fields, such as at domain walls, free surfaces, near electrodes, etc. In this paper, we apply a mesoscale model to examine the space-charge distribution at free-surface closure domain patterns in a ferroelectric thin film. The model uses a conventional electromechanical phase-field approach for ferroelectric domain patterns in combination with drift–diffusion based equations to model space-charge distribution. We additionally apply a boundary element method to compute the stray electric fields outside the ferroelectric free surface. We probe the influence of mechanical strain, such as would be applied through a substrate, on the distribution of space charge. We find an indirect, but strong, coupling between mechanics and space-charge distribution. The physical mechanism of this coupling is as follows: the mechanical strain induces changes in the domain patterns and polarization distribution; this in turn changes the local electric fields sufficiently that space charges are redistributed on the free surface rather than moving towards the bottom electrode. We note two interesting features of this coupling: first, the coupling mechanism is operative only at free surfaces due to the complex domain patterns in these regions, and would not occur in the bulk; second, although domain patterns are visually only marginally changed by the presence of space charges, the changes in electric field due to these seemingly small changes is significant and this provides the coupling with space charge.