Mechanical Stress Measurements Research Articles

Effect of Nanostructure Morphology and Concentration on the Piezoelectric Performance of Flexible Pressure Sensor based on PVDFTrFE/ Nano-ZnO Composite Thin Film

Background: The development of high-performance piezoelectric pressure sensors with outstanding sensitivity, good linearity, flexibility, durability, and biocompatibility is of great significance for smart robotics, human healthcare devices, smart sensors, and electronic skin. Thus, considerable progress has been achieved in enhancing the piezoelectric property of PVDF-TrFEbased composite pressure sensors by adding various ZnO nanostructures in PVDF-TrFE polymer acting as a nucleating agent and dielectric material. Aims: In this work, flexible pressure sensors with a sandwich structure based on PVDFTrFE/ nano-ZnO composite sensing film were fabricated using a simple spin-coating method and post-annealing process, while electrospinning and high-voltage polarization processes were not adopted. Methods: Poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)/nano-ZnO composite films were prepared via spin coating to fabricate flexible piezoelectric pressure sensors. ZnO nanoparticles (ZnO NPs), tetrapod ZnO (T-ZnO) and ZnO nanorods (ZnO NRs) were used as nano-fillers for piezoelectric PVDF-TrFE, to enhance the beta-crystal ratio as well as the crystallinity of PVDF-TrFE. The structural and surface morphologies of the composite films were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results: Among three different types of ZnO nanostructures with a concentration range (0-7.5 wt%), the sensor with 0.75 wt% ZnO NRs nanofiller exhibits a maximum output voltage of 1.73 V under an external pressure of 3 N and a maximum sensitivity of 586.3 mV/N at the range of 0-3 N. Further, the sensor can generate a clear piezoelectric voltage under bending and twisting deformation as well as compression and tensile deformation. Conclusion: To summarize, the addition of different concentrations of nano-ZnO can remarkably improve the piezoelectric performance of the composite sensor, and ZnO NRs can achieve better piezoelectric properties of the sensor as compared to ZnO NPs and T-ZnO. In addition, the sensor with 0.75 wt% ZnO NRs as nanofiller has the highest piezoelectric response, which is about 2.4 times that of the pure PVDF-TrFE sensor. It is demonstrated that the sensor has great potential applications in wearable health monitoring systems and mechanical stress measurement electronics.

Blood flow assessment technology in aortic surgery: a narrative review.

Blood flow assessment is an emerging technique that allows for assessment of hemodynamics in the heart and blood vessels. Recent advances in cardiovascular imaging technologies have made it possible for this technique to be more accessible to clinicians and researchers. Blood flow assessment typically refers to two techniques: measurement-based flow visualization using echocardiography or four-dimensional flow magnetic resonance imaging (4D flow MRI), and computer-based flow simulation based on computational fluid dynamics modeling. Using these methods, blood flow patterns can be visualized and quantitative measurements of mechanical stress on the walls of the ventricles and blood vessels, most notably the aorta, can be made. Thus, blood flow assessment has been enhancing the understanding of cardiac and aortic diseases; however, its introduction to clinical practice has been negligible yet. In this article, we aim to discuss the clinical applications and future directions of blood flow assessment in aortic surgery. We then provide our unique perspective on the technique's translational impact on the surgical management of aortic disease. Articles from the PubMed database and Google Scholar regarding blood flow assessment in aortic surgery were reviewed. For the initial search, articles published between 2013 and 2023 were prioritized, including original articles, clinical trials, case reports, and reviews. Following the initial search, additional articles were considered based on manual searches of the references from the retrieved literature. In aortic root pathology and ascending aortic aneurysms, blood flow assessment can elucidate postoperative hemodynamic changes after surgical reconfiguration of the aortic valve complex or ascending aorta. In cases of aortic dissection, analysis of blood flow can predict future aortic dilatation. For complicated congenital aortic anomalies, surgeons may use preoperative imaging to perform "virtual surgery", in which blood flow assessment can predict postoperative hemodynamics for different surgical reconstructions and assist in procedural planning even before entering the operating room. Blood flow assessment and computational modeling can evaluate hemodynamics and flow patterns by visualizing blood flow and calculating biomechanical forces in patients with aortic disease. We anticipate that blood flow assessment will become an essential tool in the treatment planning and understanding of the progression of aortic disease.

300 mm CMOS-compatible superconducting HfN and ZrN thin films for quantum applications

The rising interest in increased manufacturing maturity of quantum processing units is pushing the development of alternative superconducting materials for semiconductor fab process technology. However, these are often facing CMOS process incompatibility. In contrast to common CMOS materials, such as Al, TiN, and TaN, reports on the superconductivity of other suitable transition-metal nitrides are scarce, despite potential superiority. Here, we demonstrate fully CMOS-compatible fabrication of HfN and ZrN thin films on state-of-the-art 300 mm semiconductor process equipment, utilizing reactive DC magnetron sputtering on silicon wafers. Measurement of mechanical stress and surface roughness of the thin films demonstrates process compatibility. We investigated the materials phase and stoichiometry by structural analysis. The HfN and ZrN samples exhibit superconducting phase transitions with critical temperatures up to 5.84 and 7.32 K, critical fields of 1.73 and 6.40 T, and coherence lengths of 14 and 7 nm, respectively. A decrease in the critical temperature with decreasing film thickness indicates mesoscopic behavior due to geometric and grain-size limitations. The results promise a scalable application of HfN and ZrN in quantum computing and related fields.

Aging estimation of lithium ion cells under real-world conditions through mechanical stress measurements

Lithium-ion batteries are the storage technology employed in today's electric vehicles; however, they still have some technological limitations. Aging strongly influences battery performance and cycling induces volume variations in unconstrained cells during their life. Deformation becomes pressure as soon as there is a constraint, such as the typical cell frame used in vehicle battery modules. This work proposes to use a simple mechanical stress measurement as a marker to assess the State of Health (SOH) of a cell under real cycling and operative conditions. An experimental set-up for pouch cells was specifically designed to identify correlations between mechanical deformation, stress on the cell and SOH, in terms of capacity and internal resistance. Aging tests applied to two cells showed that cell's resistance increased by 25 % after 287 cycles and is the parameter that likely defines the battery end of life. The results revealed a relationship between capacity and cell resistance with cell pressure and deformation. Another outcome was that age-induced swelling should be considered when designing the module structure, as mechanical stresses could increase up to 31 %. The correlations identified in this work could be implemented in a Battery Management System to estimate the SOH, directly or in combination with more complex algorithms.

Strategic texturation of VO2 thin films for tuning mechanical, structural, and electronic couplings during metal-insulator transitions

Owing to its pronounced metal-insulator transition at ∼340 K, vanadium dioxide (VO2) has emerged as a promising candidate material to emulate neuronal logic and memory functions for neuromorphic computing applications. For viable implementation into practical devices, it is critical to understand the fundamental mechanical behavior of VO2 during this phase transformation. Herein, we implemented sputter deposition under various conditions to strategically texture VO2 thin films, thereby enabling us to examine the influence of crystal orientation on mechanical, structural, and electrical properties across its characteristic metal-insulator transition. Notably, polycrystalline VO2 and epitaxial VO2/sapphire (0001) films developed tension, whereas epitaxial VO2/TiO2 (001) developed compression in heating through the phase transformation. Through structural analysis, we attribute this tension/compression disparity to highly anisotropic deformation that occurs during the phase transformation. Corresponding analyses from linear elastic fracture mechanics enable the prediction of a critical film thickness, below which polycrystalline VO2 films will not fracture, which has implications for the design of resilient neuromorphic architectures. Similarly, by analyzing the stress evolution in epitaxial VO2/TiO2 (001) films, we find that fracture occurs during sputter deposition itself. Finally, we conduct simultaneous measurements of mechanical stress and electrical conductance of polycrystalline and epitaxial VO2 thin films during thermal cycling. Surprisingly, we unveiled that the orientation of the film can even alter the temperature-sequence of the macroscopic electrical response and overall stress response during the phase transformation, which we attribute to spatial heterogeneities in the transformation.

Mechanical Properties and Residual Stress Measurement of TiN/Ti Duplex Coating Using HiPIMS TiN on Cold Spray Ti

This study investigated the mechanical properties and the residual stress of high-power impulse magnetron sputtering (HiPIMS) titanium nitride (TiN) thin film capping on cold spray titanium (Ti) coating. This TiN/Ti duplex coating was deposited on the Ti substrate, and the cold spray titanium (Ti) coating was prepared in three cases with different numbers of layers. The study determined Young’s modulus, hardness, and roughness of TiN thin film and cold spray Ti coatings by nano-indentation and AFM. The residual stress measurement of TiN/Ti duplex coating was conducted using the ring-core drilling method. A focused ion beam (FIB) drilled the TiN/Ti duplex coating with various milling depth steps. The corresponding images were obtained with a scanning electron microscope (SEM). The relationship between surface deformations and relaxation stress after each milling depth step was obtained using the digital image correlation (DIC) method. The results showed TiN/Ti duplex coating exhibited excellent mechanical properties, and the residual stresses were not significantly changing with different Ti cold spray substrates, showing the feasibility of coating technology for the future applications in the aerospace industry.

MATHEMATICAL MODELING OF THE STRESS-STRAIN RELATIONS OF THE FOOT ELEMENTS IN THE CONDITIONS OF LATERAL MALLEOLUS HYPOPLASIA

One of the most common complications of long-term talocrural joint (TCJ) injury is the development of chronic instability. Among the risk factors for its occurrence - congenital or acquired shortening (hypoplasia) of the lateral malleolus of varying degrees. Objective. Determine the effect of lateral malleolus hypoplasia on the distribution of stresses in the bone and ligament elements of the foot. Methods. Mathematical modeling of the distal end of thelower extremity was performed. There are two variants of the position of the heel bone — varus and valgus with an angle of deviation from the vertical axis in both cases 15°. A vertical distributed load of 700 N was applied to the tibial plateau. On the supporting surface of the feet model's were rigidly fixed. Measurements of mechanical stresses were performed at control points. According to the criteria for estimating the stress-strain relations (SSR), the Misesstress was used. Results. It was determined that lateral malleolus hypoplasia increases the values of stresses on the lateral side of the distal tibial bone from 6.3 MPa to 6.4 MPa, from the medial — on the heel bone from 5.8 MPa to 6.0 MPa, talus from 2.1 MPa to 2.3 MPa. SSR on TCJ are also varies. In the case of a neutral position of the heel bone, lateral malleolus hypoplasia causes a decrease in the values of the ligaments on the lateral side of the TCJ,which can be explained by their elongation and, consequently, the projection increase in length In the case of varus or valgus position of the heel bone under conditions of lateral ankle hypoplasia, it was found that the varus position of the heel bone overstrains the ligaments on the lateral side, valgus - from the medial. Conclusions. Decreased stress in the ligaments of the TCJ in cases of valgus or varus position of the heel bone is one of the factors reducing the functional stability of the joint and may be the cause of its chronic instability.

Engineering of reference materials for providing traceability of measurements of mechanical stresses by acoustic type of nondestructive check

The article presents the investigation of a certified reference material (CRM) of the steels mechanical properties. At present traceability of measurement results of mechanical stresses is ensured to the standard of time, but not mechanical stresses, and a metrological approach to ensuring the uniformity of measurements of mechanical stresses requires the development of a basis for comparison.The aim of the work was the characterization and certification of standard samples of a special form, traceable to SI units-force and length, intended for transferring a unit of magnitude of mechanical stresses to measuring instruments that implement a temporary method of acoustic type of nondestructive check based on the phenomenon of acoustoelasticity. The article discusses the key stages of the development of reference materials: selection of the source material for reference materials; study of the homogeneity of the source material; carrying out experimental studies with the use of reference device (the state standard unit of strength of the 1st category) and establishing the metrological characteristics. As a result of type approval tests CRM was registered in the State Register of CRM’s as GSO 11544-2020/11545-2020. The certified characteristics of the CRM are proportional limit mechanical stress σpl; proof strength σ02 (plastic extension 0,2 %); tensile strength σв; modulus of elasticity E. Limits of the relative error of the certified values at a confidence level of 0,95 do not exceed 12 %. The authors believe that the CRM of the mechanical properties of steels GSO 11544-2020/11545-2020 will provide metrological traceability of the results of measurements of mechanical stresses by measuring instruments that implement the by acoustic type of nondestructive check, when using the GSO as a basis for comparison in the verification scheme.

METHOD FOR DETERMINING THE PHENOMENON OF STALL ON HELICOPTER BLADE

The analysis of dangerous factors leading to the phenomenon of flow stall on the rotor blades of a helicopter has been carried out. The estimated cruising speed of a helicopter without auxiliary propulsion at the current level of technology development lies in the range of 280-370 km/h. The results of flight experiments showed that the stall phenomenon leads to a sharp increase in the load on the blades, which in turn is transferred to the lower fixed plate of the swashplate. This phenomenon is accompanied by the appearance of the n-th harmonic of the main rotor speed. The results of these experiments made it possible to create a subsystem for recognizing the phenomenon of stall with the issuance of visual and audible indication to the pilot to change the flight mode. A block diagram and description of the operation of the subsystem based on the simultaneous use of two features are given: measurement of mechanical stresses on the swashplate and the amplitude of the harmonic component of the signal from the frequency of rotation of the rotor blades of the helicopter. The use of two signs can significantly increase the probability of determining the moment of flow stall. The technical implementation of the proposed method for determining the phenomenon of flow stall on the rotor blades of a helicopter makes it possible to provide a qualitatively new level of flight safety under conditions of complex maneuvers.

Methodology for assessing the uncertainty of measurements of mechanical stresses by the ultrasonic method with the help of an optical-acoustic separate-combined transducer

The work is devoted to the ultrasonic method of controlling mechanical stresses using ultrasonic head waves. The factors that contribute to the result of measurements of mechanical stresses include: the propagation velocity of the head ultrasonic wave, the temperature of the environment and the object of control, the coefficients of acoustoelastic and thermoacoustic coupling, parameters of the optical-acoustic transducer. The contribution of each of these factors to the results of measurements of mechanical stresses is assessed. A technique for assessing the uncertainty of measurements of mechanical stresses by the ultrasonic method using head waves has been developed.

Tuning the stress state in Nb-thin films by lateral size confinement

For 5 nm thin Nb films adhered to a rigid substrate, hydrogen absorption leads to ultrahigh mechanical stress of about -8 GPa. This is related to a purely elastic behaviour. The high mechanical stress destabilizes phases and even suppresses conventional two-phase regions known for the Nb-H bulk system. These unique thin film properties can be preserved to thicker films, by lateral confinement. Nb-Fe films provide a laterally confined columnar domain structure of well-separated α-Nb(Fe) and μ-FeNb phases. While the α-Nb(Fe) absorbs hydrogen at low chemical potentials, the μ-FeNb phase does not, separating the two phases into a hydrogen active and a hydrogen passive one. The behaviour of 75 nm Nb-Fe films was studied by in situ mechanical stress measurements, in situ x-ray diffraction and transmission electron microscopy. With increasing Fe-content, Nb-Fe films show a strong increase in the yield stress upon hydrogen absorption. This allows for an extended elastic range and high maximum stress values of -4.6 GPa, for 75 nm Nb-Fe films. X-ray diffraction pattern collected upon hydrogen loading of Nb-Fe films show peak shifts and intermediate peak broadening. This indicates the presence of a two-phase region and preservation of the lattice coherency between the α-Nb(Fe)-H phase and the hydride phase. Peak shifts indicate a reduced vertical expansion of the hydrogen absorbing α-Nb(Fe) lattice. This is attributed to the presence of the µ-FeNb phase. FEM simulations on Nb-Fe-H films confirm reduced overall expansions and lateral stresses, when compared to pure Nb-H films. High vertical stresses arise upon H-loading due to the link between the two Nb-Fe phases. These stresses are tensile for µ-FeNb and compressive for the α-Nb(Fe) domains and also reach values of several GPa. Conservation of the exceptional thin film properties to thicker films by lateral confinement is suggested to be a powerful strategy for many different applications like sensor technologies or energy storage.

Mechanical Properties and Residual Stress Measurements of Grade IV Titanium and Ti-6Al-4V and Ti-13Nb-13Zr Titanium Alloys after Laser Treatment.

Nowadays, surface engineering focuses on research into materials for medical applications. Titanium and its alloys are prominent, especially Ti-6Al-4V and Ti-13Nb-13Zr. Samples made of pure grade IV titanium and the titanium alloys Ti-6Al-4V and Ti-13Nb-13Zr were modified via laser treatment with laser beam frequency f = 25 Hz and laser beam power P = 1000 W during a laser pulse with duration t = 1 ms. Subsequently, to analyze the properties of the obtained surface layers, the following tests were performed: scanning electron microscopy, chemical and phase composition analysis, wetting angle tests and roughness tests. The assessment of the impact of the laser modification on the internal stresses of the investigated materials was carried out by comparing the values of the stresses of the laser-modified samples to those of the reference samples. The obtained results showed increased values of tensile stresses after laser modification: the highest value was found for the Ti-6Al-4V alloy at 6.7434 GPa and the lowest for pure grade IV titanium at 3.742 GPa. After laser and heat treatment, a reduction in the stress was observed, together with a significant increase in the hardness of the tested materials, with the highest value for Ti-6Al-4V alloy at 27.723 GPa. This can provide better abrasion resistance and lower long-term toxicity, both of which are desirable when using Ti-6Al-4V and Ti-13Nb-13Zr alloys for implant materials.

METHODOLOGY FOR EVALUATION THE UNCERTAINTY OF MEASUREMENT OF MECHANICAL STRESS BY THE ULTRASONIC METHOD WITH THE HELP OF AN OPTICAL-ACOUSTIC SEPARATE-COMBINED TRANSDUCER

The work is devoted to the ultrasonic method for controlling mechanical stresses using ultrasonic head waves. The speed of the head ultrasonic wave is the highest, which allows it to be recorded stably among other types of ultrasonic waves and noises. To determine mechanical stresses, registration of the relative change in the velocity of propagation of the head ultrasonic wave is used, corrected for the change in the measured value caused by the change in the temperature of the test object. Thus, mechanical stresses are not measured directly, but the sources of uncertainty are the results of measurements of the propagation velocity of the head ultrasonic wave, the temperature of the environment and the test object, the coefficients of acoustoelastic and thermoacoustic coupling, and the parameters of the optical-acoustic transducer. The contribution of each of these factors to the results of measurements of mechanical stresses is estimated. On the basis of GOST 34100.3–2017, a method has been developed for asessing the uncertainty of measurements of mechanical stresses by the ultrasonic method using head waves. The dependence of the expanded measurement uncertainty on the value of the measured mechanical stresses was obtained. This dependence shows that measurements of mechanical stresses in the range of less than 100 MPa have an uncertainty of more than 10 % of the measured value. When measuring mechanical stresses over 200 MPa, the measurement uncertainty will not exceed 4 % (at a confidence level of 95 %).The proposed approach to assessing the uncertainty of measurements of mechanical stresses can be useful in the development of requirements for the used measuring instruments, alignment samples and control objects, as well as in the development of methods for monitoring mechanical stresses by the ultrasonic method using an optical-acoustic separate-combined transducer.

РАСЧЕТ МОДЕЛИ ЭТАЛОННОЙ УСТАНОВКИ ДЛЯ СОЗДАНИЯ ПОЛЯ МЕХАНИЧЕСКИХ НАПРЯЖЕНИЙ

The paper concerns the problem of practical measurement of mechanical stresses in industrial objects. The signal dependencies of different nondestructive testing devices on the stresses are discussed. Results of numerical modeling of the mechanical stresses that can be reproduced by the suggested standard machine are presented. A number of questions that should be solved to turn nondestructive testing into the measurements of mechanical stresses is discussed.

Ultrahigh-Sensitive Compression-Stress Sensor Using Integrated Stimuli-Responsive Materials.

Measurement of mechanical stresses, such as compression, shear, and tensile stresses, contributes toward achieving a safer and healthier life. In particular, the detection of weak compression stresses is required for healthcare monitoring and biomedical applications. Compression stresses in the order of 106 -1010 Pa have been visualized and/or quantified using mechano-responsive materials in previous works. However, in general, it is not easy to detect compression stresses weaker than 103 Pa using conventional mechano-responsive materials because the dynamic motion of the rigid mechano-responsive molecules is not induced by such a weak stress. In the present work, weak compression stresses in the order of 100 -103 Pa are visualized and measured via the integration of stimuli-responsive materials, such as layered polydiacetylene (PDA) and dry liquid (DL), through response cascades. DLs consisting of liquid droplets covered by solid particles release the interior liquid and collapse with application of a weak compression stress. The color of the layered PDA is changed by the spilled liquid as a chemical stress. A variety of weak compression stresses, such as expiratory pressure, are visualized and colorimetrically measured using the paper-based device of the integrated stimuli-responsive materials. Diverse mechano-sensing devices can be designed via the integration of stimuli-responsive materials.

Serial MRI-based right ventricular mechanical wall stress measurements and their association with right ventricle function in patients with repaired Tetralogy of Fallot

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Stichting Hartekind en Thorax Foundation Background Optimal timing of pulmonary valve replacement (PVR) in Tetralogy of Fallot (TOF) patients remains challenging. Wall stress is considered to be a possible early marker of right ventricular (RV) dysfunction. With patient-specific computational models, wall stress can be determined regionally and with high accuracy, especially in complex shaped ventricles such as in TOF patients. We aimed to 1) develop patient-specific computational models to assess RV diastolic wall stresses and 2) investigate the association of wall stresses and their change over time with functional parameters in TOF patients. Methods Repaired TOF patients with at least moderate pulmonary regurgitation (PR) and prior to PVR were included. MRI-based patient-specific computational ventricular models were created (figure). The ventricular geometry was created by stacking endo- and epicardial contours traced on short axis SSFP cine images. Pressure in the right ventricle was estimated from echocardiography. Mid-diastolic wall stress in the RV free wall was analysed globally and regionally (basal, mid, apical, anterior, lateral and posterior) at two time points. RV ejection fraction (RVEF), NT-proBNP and exercise tests (% maximum predicted workload) were used as outcomes for RV function. Associations between wall stresses and outcomes were investigated using linear mixed models adjusted for follow-up duration. Results Five males and five females were included with an age at baseline of 24 (IQR 16-28) years and RV end-diastolic volume of 140 (IQR 127-144) ml/m2. The period between the two time points was 7.0 (IQR 5.8-7.3) years. Global wall stress of the RV free wall combining both time points was 5.8 kPa (IQR 5.2-7.2). There was no statistical difference between baseline and follow-up global wall stress. The mean wall stresses in the mid region was 1.69 kPa (p < 0.01) higher than in the basal region and was 1.05 kPa (p = 0.03) higher than in the apical region cross-sectionally. The wall stress also increased more in the mid region compared to basal and apical region, corrected for duration of follow-up. Patients with more severe PR at baseline demonstrated a higher increase of global wall stress over time (p = 0.02), especially in lateral free wall. Higher global free wall stresses were cross-sectionally independently associated with lower RVEF, adjusted for LVEF and RVEDV (β=-1.29 % RVEF per kPa increase in wall stress, p = 0.01). This association was most prominent in the anterior, basal and mid part. No statistically significant association was found between wall stress, NT-proBNP, and exercise capacity. Conclusions This study generated a novel MRI-based method to calculate wall stress in geometrically complex ventricles. Wall stress associated negatively with RVEF in patients with TOF and PR. This promising tool for RV wall stress analysis can be used in future larger studies to validate these preliminary findings and to assess the predictive value of wall stress in TOF. Abstract Figure.

Measuring the Internal Stress in Ovine Meniscus During Simulated In Vivo Gait Kinematics: A Novel Method Using Fibre Optic Technology.

Changes in stress transferred across articular joints have been described as a substantial factor in the initiation and progression of joint disease such as post-traumatic osteoarthritis and have thus been of interest to biomechanical researchers. However, to date, stress magnitudes within the menisci have not been successfully measured. In this study, a novel method for measuring stress within the menisci is presented. Small Fibre Bragg Grating (FBG) sensors were inserted inside menisci and used to measure mechanical stress during replicated gait cycles. In-vitro stress measurements within the menisci were preformed for healthy gait and gait following surgical damage to the joints. Together with our capability to reproduce in vivo motions accurately, the improvements in fibre optic technology have allowed for the first direct measurement of mechanical stress in menisci.

Silicon solar cell–integrated stress and temperature sensors for photovoltaic modules

AbstractWe propose silicon solar cell–integrated stress and temperature sensors as a new approach for the stress and temperature measurement in photovoltaic (PV) modules. The solar cell–integrated sensors enable a direct and continuous in situ measurement of mechanical stress and temperature of solar cells within PV modules. In this work, we present a proof of concept for stress and temperature sensors on a silicon solar cell wafer. Both sensors were tested in a conventional PV module setup. For the stress sensor, a sensitivity of (−47.41 ± 0.14)%/GPa has been reached, and for the temperature sensor, a sensitivity of (3.557 ± 0.008) × 10−3 K−1 has been reached. These sensors can already be used in research for increased measurement accuracy of the temperature and the mechanical stress in PV modules because of the implementation at the precise location of the solar cells within a laminate stack, for process evaluation, in‐situ measurements in reliability tests, and the correlation with real exposure to climates.

Stress self-sensing in Amplified Piezoelectric Actuators through a fully-coupled model of hysteresis

Piezoelectric actuators are among the most used devices for micro-positioning applications. Yet, their output displacement shows non-negligible hysteresis effects with respect to both the input voltage and the mechanical stress and, as a consequence, an accurate control system has to be designed, taking into account the mechanical stress measurement too. This task is usually addressed by exploiting external bulky force sensors, e.g. load cells. A novel stress self-sensing approach is proposed in this paper, which allows the stress estimation by simply exploiting the measurement of electrical voltage and current of the piezoelectric stacks. In particular, a thermodynamic consistent fully-coupled multi-input multi-output model of hysteresis is exploited. The method is applied for the first time to a commercial Amplified Piezoelectric Actuator with a crossbow-like amplification system. An experimental validation of the approach is proposed and discussed.

Microscopic Imaging of the Stress Tensor in Diamond Using in Situ Quantum Sensors

The precise measurement of mechanical stress at the nanoscale is of fundamental and technological importance. In principle, all six independent variables of the stress tensor, which describe the direction and magnitude of compression/tension and shear stress in a solid, can be exploited to tune or enhance the properties of materials and devices. However, existing techniques to probe the local stress are generally incapable of measuring the entire stress tensor. Here, we make use of an ensemble of atomic-sized in situ strain sensors in diamond (nitrogen-vacancy defects) to achieve spatial mapping of the full stress tensor, with a submicrometer spatial resolution and a sensitivity of the order of 1 MPa (10 MPa) for the shear (axial) stress components. To illustrate the effectiveness and versatility of the technique, we apply it to a broad range of experimental situations, including mapping the stress induced by localized implantation damage, nanoindents, and scratches. In addition, we observe surprisingly large stress contributions from functional electronic devices fabricated on the diamond and also demonstrate sensitivity to deformations of materials in contact with the diamond. Our technique could enable in situ measurements of the mechanical response of diamond nanostructures under various stimuli, with potential applications in strain engineering for diamond-based quantum technologies and in nanomechanical sensing for on-chip mass spectroscopy.