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BACKGROUND RESULTS CONCLUSION Intelligent identification and precise plucking are the keys to intelligent tea harvesting robots, which are currently of increasing significance. Aiming at plucking tender leaves for high‐quality green tea production, in this study, a tender leaf identification algorithm and a mechanically perceptible plucking finger have been proposed.Based on the segmentation algorithm and color features, the tender leaf identification algorithm shows an average identification accuracy of over 92.8%. The mechanically perceptible plucking finger plucks tender leaves in a way that a human hand does, aiming to maintain the high quality of tea products. Though finite element analysis, we determine the ideal size of grippers and the location of strain gauge attachment on a gripper to enable the employment of feedback control of desired gripping force. As revealed in our experiments, the success rate of tender leaf plucking reaches 92.5%, demonstrating the effectiveness of our design.The results show that the tender leaf identification algorithm and the mechanically perceptible plucking finger are effective for identification of tender leaves and plucking, providing a foundation for the development of an intelligent tender leaf plucking robot. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This study designs a blasting loading device capable of changing the utilization of explosive gas by modifying the constraint conditions. The propagation of crack and stress waves in red sandstone under different explosive gases is recorded using digital image correlation technology and ultra‐dynamic strain gauges. Both methods are effectively validated against each other. The results showed that as the utilization of explosive gas increases, the explosive stress wave induces layer cracking at the specimen's far end and tensile failure at its near end. In addition, the larger the stress wave's amplitude, the greater the spatial attenuation coefficients of the compression and tension waves. The study ultimately deduces the propagation process of the incident wave and analyzes the influence of stress wave propagation on the specimen's failure characteristics. [ABSTRACT FROM AUTHOR]

The sense of touch and perception of hand motion form an essential part of the somatic sensory system. Although piezoelectric sensors demonstrate high sensitivity and linearity, they are traditionally not employed for electronic skins because of their limited stretchability. Here, a printed, skin‐conformal, electronic system consisting of stretchable piezoelectric pressure sensors and carbon nanotube strain gauges capable of identifying tactile sensations and joint movements on the hand is introduced. The pressure sensor demonstrates both high sensitivity (19.9 mV kPa−1) and linearity (0.1–1000 kPa) while being reliably stretchable to above 15%. To complement the pressure sensing functionality, a strain gauge is fabricated in a rapid stamp printing process and designed to demonstrate excellent mechanical reliability with up to 70% strain and high sensitivity (36.5‐gauge factor). These sensors can seamlessly conform to numerous anatomical regions and cover wide areas of the skin, making them ideal for deployment in an electronic skin. Finally, the sensors are integrated with a flexible microelectronic device to demonstrate their functionality in human touch and prosthetic hand applications. [ABSTRACT FROM AUTHOR]

A novel laser thermal printing technique toward the fabrication of all‐in‐one flexible intelligent devices is presented in this work, addressing the existing challenges in their scalable manufacturing and multifunctional performance. The first‐ever application of this technique for the synthesis of a multifunctional intelligent cobweb structure is presented. The resultant cobweb integrates a conductive network of multi‐walled carbon nanotubes (MWCNTs) and NdFeB magnetic microparticles within a polydimethylsiloxane (PDMS) matrix, enabling seamless incorporation of sensing, stimulus response, and actuation functionalities. The cobweb exhibits multifunctional sensing characteristics, including a 2.37 strain gauge factor and a 0.312%·mT−1 magnetic field sensitivity, excellent stability exceeding 3500 cycles. Furthermore, the cobweb achieves accurate capture of a beetle on the basis of real‐time sensing of the beetle, verifying its rapid stimulus response characteristics. Meanwhile, the cobweb exhibits an electromagnetic ejection performance with an ejection height of over 33.5 times the size of the projectile, verifying its powerful actuating ability. These results demonstrate the successful integration of multifunctional sensing, stimulus response, and actuation within the cobweb structure, facilitated by the innovative laser thermal printing process. The laser thermal printing technique marks a significant advancement in the efficient fabrication of miniaturized and multifunctional flexible intelligent devices based on thermosetting materials. [ABSTRACT FROM AUTHOR]

Benign, locally aggressive tumors of the distal femur are typically treated with intralesional curettage and polymethylmethacrylate (PMMA) cementation. However, it is not known whether plate fixation should be added to biomechanically augment these PMMA‐filled defects. The purpose of this study was to evaluate the performance of two competing techniques for reconstruction of a distal femoral defect. For this biomechanical study, we used 12 composite femurs with properties comparable to bone. In nine femurs, identical contained medial distal femoral defects were created using a robotic arm. Group A contained three intact femurs, Group B three femurs with an unfilled defect, Group C three femurs reconstructed with PMMA alone, and Group D three femurs reconstructed with PMMA plus a medial locking plate. Locations of greatest stress concentration were determined by PhotoStress analysis, then three strain gauges were applied to each specimen at these high‐stress locations. Specimens were loaded within a physiologic range followed by loading to failure. Outcome measures included construct stiffness, strain along the distal femur, and load at failure. Results showed that stiffness and strain were not significantly different between reconstructive techniques; however, both techniques reduced tensile strain along the popliteal surface by approximately 40% compared to non‐reconstructed specimens. All specimens failed at the femoral neck before failing at the distal femur. These findings suggest that plate augmentation of PMMA‐filled distal femoral defects like the one in this study offers insignificant biomechanical benefit within physiologic loads and therefore may be unnecessary. [ABSTRACT FROM AUTHOR]

Extrusion tests were conducted on recycled coarse aggregate concrete with circular steel tubes (RCCST, 100% replacement of recycled coarse aggregate) to investigate the impact of freeze–thaw cycles on bond properties. RCCST samples were subjected to 0, 25, 50, 75, 100, 125 and 150 freeze–thaw cycles and their bond properties were then compared with those of natural coarse aggregate concrete with circular steel tubes (NCCST) after 0, 100 and 150 freeze–thaw cycles. The experimental results indicate that freeze–thaw cycling damages the internal structure of RCCST, causing a significant decrease in interfacial bond strength with an increase in the number of freeze–thaw cycles. Freeze–thaw RCCST exhibits lower peak load and higher peak slip compared to NCCST, with increases of 25.2%, 73.2%, and 70.3% after 0, 100, and 150 freeze–thaw cycles, respectively. Regression analysis was used to derive an exponential equation that describes the relationship between longitudinal strain and strain gauge position. Additionally, a segmented fitting method was employed to obtain an expression for the bond slip of the freeze–thaw RCCST with a circular steel pipe. [ABSTRACT FROM AUTHOR]

The checkerboard constitutes the best pattern for full‐field strain measurement because it maximizes image gradient. In the experimental mechanics community, employing this pattern is currently strongly limited because depositing it on the surface of specimens raises practical difficulties. A recent study shows, however, that it is technically possible by using a laser engraver. The present paper aims to push this solution forward by printing a checkerboard pattern on a thin polymeric film and then gluing the resulting laser‐engraved film on the specimen surface. The underlying idea is to separate the manufacturing process of this optical strain gauge on the one hand and its use on the other hand to help spread this strain measuring tool in the experimental mechanics community. The polymeric film employed here is the same as that used in the manufacturing process of classic electrical gauges, so one can rely on the know‐how of classic strain gauge bonding to glue this optical strain gauge on the specimen surface. The main difference between the proposed tool and classic electrical gauges is that the strain field beneath the polymeric support is measured instead of localized strain values. The paper is a proof of concept for this strain field measuring tool. The manufacturing and bonding processes are described in the paper. The localized spectrum analysis, a spectral technique developed for processing images of periodic patterns, is used to retrieve the strain fields from checkerboard images. Through two complementary examples, we show the ability of this new type of strain gauge to detect and quantify local details in the strain field beneath. A simplified 1D model is also proposed to assess the minimum width of the strain peak that can reliably be measured with this technique. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) is a technology aimed to monitor the soundness of the structures. Applications for aircraft structures are largely investigated. The goal is to utilize the information acquired during the monitoring to save maintenance costs, improve flight safety, and design lighter structures. Different issues, like load monitoring and impact detection, are investigated by SHM research. The most largely investigated issue is damage detection, i.e., developing a system that utilizes sensors to detect the damage in the structure. Damage detection can be performed with two sensors: dynamic and static. Dynamic sensors work by transmission of waves through the structures. Defects are identified by deviation and reflection of the waves by damages. The SHM approach described in this work is based on static sensors, like strain gages or fiber optics. The strain fields under load in pristine and damaged conditions are compared; the evaluation of the change in the strain field identifies damages. Two different algorithms for damage detection have been developed and patented in Leonardo Aircraft and are described in this work; they are based on the reverse finite element model (FEM) and neural network. The issues related to the strain field measurement are also briefly described. [ABSTRACT FROM AUTHOR]

Effective transmission of stress between fillers and the host matrix is instrumental in enhancing the properties of nanocomposites and optimizing filler reinforcement. This study delves into understanding stress transfer in materials, exploring the impact of synthesis methods and matrix materials through a comprehensive examination of a bilayer graphene (BLG)‐polydimethylsiloxane (PDMS) nanocomposite. BLG was synthesized via chemical exfoliation and subjected to various strain conditions within a PDMS matrix. A precisely controlled strain, ranging from 0% to 0.19%, was applied using a meticulous 4‐point bending method, monitored with a standard strain gauge. The study unveiled significant shifts in the Raman spectra's 2D band, indicating a direct linear relationship with applied strain. Utilizing contour mapping techniques on well‐defined Raman spectra and stress‐induced band shifts, we mapped strain distribution within the BLG layer. The results revealed a gradual increase in strain from the lower to the upper end of the BLG structure, resembling strain behaviors observed in differently shaped fibers. These compelling findings advance our understanding of strain dynamics within BLG‐PDMS nanocomposites, highlighting the crucial role of strain mapping methodologies in scrutinizing the material's structural response to deformation. Highlights: The study reports successful synthesis of high‐quality bilayer graphene (BLG) using a chemical exfoliation method, as evidenced by the sharp 2D and G Raman peaks.Significant shifts in 2D band exhibited linear correlation between applied strain; observed within precise strain levels of 0% to 0.19%.Contour maps revealed a gradual increase in strain from the lower to the upper end of the BLG structure, akin to strain behaviors observed in differently shaped fibers. [ABSTRACT FROM AUTHOR]

Flexible strain sensors are widely used in the fields of human motion monitoring, electronic skin, and soft robotics. In this work, to satisfy the demand for high‐sensitivity, low‐cost, and fast‐response flexible strain sensors for these fields, embedded 3D printing (E‐3DP) technology is employed to fabricate highly sensitive and fast‐responding flexible strain sensors. The effects of conductive carbon paste concentration and printing process parameters by establishing the E‐3DP system on the piezoresistive behavior of the sensor were investigated. The results show that the gauge factor of the strain sensor is about 36.1 and 247.67, under the strain of 0%–40% and 40%–45%, respectively. Its response/recovery time is about 250/350 ms. On this basis, the sensor can also accurately sense and distinguish the motion in distinct parts of the human body, demonstrating that the flexible strain sensor manufactured by the method possesses the potential to be widely used in the fields of human motion monitoring, electronic skin, and soft robotics. [ABSTRACT FROM AUTHOR]

The strain on the cell casing can serve as an indicator of the internal state of the cell. Monitoring strain during the charging and discharging processes aids in determining optimal charging and discharging operations, thereby maximizing the lifespan and performance of the battery. Herein, strain dynamic curves are obtained for lithium‐ion batteries at low, medium, and high charge and discharge rates by affixing strain gauges to individual cells. The investigation delves into parameters such as strain relaxation time, maximum strain, and residual strain at various charge rates and states of charge. The experimental findings reveal distinctive patterns, indicating that the strain curve during high‐rate charging resembles a second‐order function, exhibiting more pronounced fluctuations as the rate increases. This stands in stark contrast to the strain exponential decay observed during conventional medium and low‐rate charging. Notably, the strain residual resulting from high‐rate charging proves to be several times higher than that observed in low‐rate charging, hinting at potential differences in the dynamic distribution of lithium ions within batteries during high‐rate versus medium‐low‐rate charging modes. [ABSTRACT FROM AUTHOR]

This study describes a novel stretchable and very sensitive strain gauge enabled by laser‐joining carbon nanotubes, resulting in unique architectures forming macroscopic web networks. The stiffness of the resistive strain sensor created by laser material patterning is reduced significantly, from 1.5824 to 0.142 kN m−1, corresponding to a change in laser power from 0 to 0.436 W. Many benefits of laser‐based bonding include precise and flexible local pattern production with minimal energy impact on the flexible substrate. Furthermore, the maximum Gauge factor of the sensor exhibits diverse trends with different strains, generating values of GF = 12.8 for strains less than 2.5% and GF = 165 for strains greater than 2.5% during extension‐retraction cycles. These disparities are the result of a dynamic fight between network degradation and regeneration. [ABSTRACT FROM AUTHOR]

Fault reactivations induced by deep excavation can pose significant challenges to underground construction or resource extraction. Laboratory experiments on rock faults demonstrate that unloading‐induced fault reactivations obey the Coulomb failure criterion derived from loading‐induced events. However, the effect of stress path during unloading on the failure criterion and rupture dynamics of fault reactivations remains poorly understood. Here, we present findings from a series of laboratory experiments aimed at elucidating the effect of the unloading path on the failure criterion and rupture dynamics of fault reactivations. We conducted experiments under various stress conditions, examining two cases of unloading paths. In Case I, we unloaded the minimum principal stress, while in Case II, the maximum principal stress was unloaded. Strain gauges and high‐speed photography were employed to capture the transient dynamic rupture process. Our investigations have yielded new insights into the effect of unloading path on the rupture dynamics when the fault is reactivated. In Case I, we observed fault reactivations resembling those loading‐induced events characterized by forward sliding. Conversely, in Case II, fault reactivations associated with stress reversal produce mild reversed sliding with lower stress drop and rupture velocity. Furthermore, we find that there is a remarkable reduction in static friction for reversed sliding, indicating that the failure criterion for fault reactivation is influenced by the stress path. We demonstrate that enhanced stress heterogeneity, caused by stress reversal, serves as a mechanism for reduced static friction. These findings contribute to our understanding of the mechanisms underlying fault reactivations, particularly those involving reversed sliding. Plain Language Summary: It is known that underground excavation, accompanied by stress release, can trigger fault reactivation, resulting in induced earthquakes. Understanding how unloading affects the activation and rupture dynamics of these induced events is crucial. To investigate the role of unloading path, we conducted laboratory experiments to simulate unloading‐induced fault reactivation on analog material containing a fault. Loadings are applied biaxially at the boundary. We observed that unloading the minimum principal stress (i.e., reducing the minimum loading) could reactivate the fault, generating forward sliding resembling loading‐induced rupture events. Conversely, unloading the maximum principal stress (i.e., reducing the maximum loading) induces reversed sliding, featuring smaller stress drop, coseismic slip, and rupture speed compared to forward sliding. Moreover, the static friction coefficient is reduced prior to reversed sliding. We also found that enhanced stress heterogeneity prior to unloading‐induced reversed sliding can account for the difference in static friction coefficient. Therefore, it is necessary to incorporate the effect of loading path into the studies of fault reactivation. Key Points: Rupture process of unloading‐induced fault reactivation is dictated by the initial stress state and stress pathThe static friction of fault is reduced for the unloading‐induced reversed slidingEnhanced stress heterogeneity caused by stress reversal contributes to reduced static friction [ABSTRACT FROM AUTHOR]

This article presents beta‐gallium oxide (β‐Ga2O3) micro electro mechanical systems (MEMS) strain/pressure sensors as a way to enhance sensitivity. The model consists of four piezoresistive strain gauges connected in a Wheatstone bridge configuration. The MEMS model is simulated from 0 Pa to 50 kPa, resulting in an output signal range of −3–16 mV and a responsivity of 0.38 mV kPa−1. The simulation also shows that as temperature increases, the resistance of the piezoresistive material in the MEMS decreases, leading to changes in the output signals. The reliable device effectively utilizes the full Wheatstone bridge configuration to compensate for temperature‐related influences. These early results suggest that Ga2O3‐based MEMS devices have great potential for use in high‐temperature pressure sensor applications in the future. [ABSTRACT FROM AUTHOR]

The roughness of 3D‐printed surfaces poses a challenge when integrating fused filament fabrication (FFF) printing with printed electronics, leading to inconsistencies and breaks in the circuit traces. To improve the surface roughness, an ironing toolpath is proposed. The ironing toolpath involves the hot nozzle going over the printed surface with finer line spacing, remelting the surface to fill gaps, and creating a smooth finish. For further optimization, various ironing parameters are investigated including flow, speed, line spacing, and temperature. A wide range of materials is tested, including commonly used low‐temperature filaments (polylactic acid, polyethylene terephthalate, acrylonitrile butadiene styrene) and high‐temperature filaments (polysulfone, polyetherimide, polyether ether ketone) suitable for integration with printed electronics and medical applications. To collect the extensive datasets, an automated measurement system is deployed. With this method, surface roughness reductions of up to 96.6% are achieved and significant trends are identified. Lastly, the integration of 3D printing with electronics is demonstrated by printing a high‐resolution strain gauge structure on top of an ironed surface and embedding it into fully printed tweezers which can be used in medical robotics. The insights on ironing extend beyond electronics and can also be valuable in other areas where low surface roughness of FFF‐printed parts is required. [ABSTRACT FROM AUTHOR]

In the energy production and transportation industries, numerous metallic structures may be subjected to at least several billions of cycles, i.e. loaded in the very high cycle fatigue domain (VHCF). Therefore, to design structures in the VHCF domain, a reliable methodology is necessary. One useful quantity to characterize plastic activity at the microscopic scale and fatigue damage evolution is the mechanical work supplied to a material. However, the estimation of this mechanical work in a metal during ultrasonic fatigue tests remains challenging. This paper aims to present an innovative methodology to quantify this. An experimental procedure was developed to estimate the mechanical work from stress and total strain evolution measurements during one loading cycle with a time accuracy of about 50 ns. This was achieved by conducting time-resolved X-ray diffraction coupled to strain gauge measurements at a synchrotron facility working in pulsed mode (single-bunch mode). [ABSTRACT FROM AUTHOR]

The article presents a dual‐optimized adaptive algorithm based on continuous wavelet transform and derivative precise peak capture is developed for fiber cavity ring‐down spectroscopy. Adaptive spectral signal processing is achieved so that peak selection blindness can be effectively solved. To verify the performance of the dual‐optimized adaptive algorithm, a highly sensitive refractive index sensor using a bandgap fiber‐based linear fiber cavity is demonstrated. The developed dual‐optimized adaptive algorithm is compared with the conventional maximum extraction algorithm, and the results show that the dual‐optimized adaptive algorithm has a better performance in suppressing noise and processing superimposed peaks. A stable enhancement factor of 5 is obtained, indicating that the newly developed dual‐optimized adaptive algorithm can generate a high‐quality cavity ring‐down spectrum for applications including refractive index sensors, biosensors, strain gauges, and pressure sensors. [ABSTRACT FROM AUTHOR]

Exposed column base (ECB) connections are widely used in low‐ and mid‐rise steel moment‐resisting frames (MRFs). In this study, we investigated the impact of ECB damage on the overall seismic properties of low‐rise MRFs. A novel method was proposed to evaluate the post‐earthquake conditions of steel frame structures based on the coupling coefficient (CC). Using only the strain gauge data of the columns in the bottom storey, a method using a modified CC was adopted to classify the degree of damage by estimating the residual capacity of the MRF and predicting the future seismic response under specific intensity levels of hypothetical earthquakes, considering both the structural and non‐structural components. The limit values of CC were obtained by solving the deduced equations. Finite element analyses were conducted to validate the proposed method. The method was applied for calculating the test data of a four‐storey MRF tested at the E‐Defense shaking table facility. Four loading cases comprising six groups of monitored data in the X‐ and Y‐directions were used in this study. A comprehensive and systematic evaluation result was eventually obtained, and the accuracy of the method was validated. [ABSTRACT FROM AUTHOR]

Given the rising demand for cold brew coffee, innovative approaches are required to address the present difficulties in its production. This motivates the consideration of the planetary rotating bed reactor (PRBR) as a solid–liquid extraction technology. The PRBR consists of cylindrical mesh chambers that contain the solid phase and move in two superimposed rotations. This motion pattern enhances mass transfer through alternating radial forces: the pushback effect (PBE). To evaluate the utility of the PRBR and the role of PBE, we investigated the kinetics and energy demand of cold brew coffee extraction. For this purpose, we varied rotational speeds and PBE conditions in a 1 L lab‐scale reactor. Kinetics was determined by in‐line monitoring of electrical conductivity correlated with the eluate's weight‐based total dissolved solids and caffeine by high‐performance liquid chromatography. Energy consumption was derived from strain gauge torque measurements. Our findings reveal that saturation of the extraction rate with respect to the rotational speed is evident both with and without PBE. However, PBE significantly reduces extraction time by 75% while requiring 60% less mechanical energy. The fastest conditions probed 95% of the maximum extraction yield within 12 s, effectively being >99% faster than static immersion. We believe these findings, along with further procedural advantages, qualify the PRBR as a viable technology for cold brew coffee production. Practical Applications: The relevance of an economical and sustainable preparation of cold brew coffee extends from the industrial to the gastronomic to the domestic environment. Challenges and limitations relate to process time, particle separation, product and extraction yield, and taste problems due to over‐extraction. The planetary rotating bed reactor (PRBR) promises to address all these issues by combining extraction and separation in a simultaneous and ultrafast process. The present study confirms the superiority of PRBR's action mechanisms in terms of rapidity and energetic efficiency for extraction. Due to the excellent scalability of both the design and the physical effect, the PRBR is intended for large‐scale production of ready‐to‐drink products and local production in coffee shops or private households. By modifying the particle feed, even continuous operation is conceivable. Further applications are, for example, dry‐hopping of beer, fast‐aging of spirits, and preparation of various liquid foods. [ABSTRACT FROM AUTHOR]

This research introduces a novel flexible spherical carbon nanoparticle-based polyurethane conductive ink, which is employed to fabricate strain sensors by a lab-developed direct ink writing/3D printing system. Rheological tests are performed, and sensors are pasted on glass fiber-reinforced plastic specimens to study strain gauge behaviors under quasistatic loading. The gauge factor in tensile loading is found to be layer width dependent as decreasing the strain gauge's layer width increases the sensitivity of the strain sensor. A maximum gauge factor of 34 is achieved using a layer width of 0.2 mm, 17 times greater than commercially available metal foil strain gauges. The four-point bend tests are performed under tension/compression to assess the sensor's strain-sensing and damage-monitoring ability. Fractographic analysis is coupled with strain monitoring using the developed sensor, which confirms that the failure progresses from intralaminar failure modes such as ply splitting in tension. At the same time, delamination leads to kink band formation under compression and the eventual failure of load-bearing fibers. The developed sensor exhibits repeatable performance with low hysteresis and integrated nonlinearity errors for up to 1000 cycles. The developed sensors could be effectively employed for online in situ structural health monitoring of aerospace structures under static and dynamic loading. [ABSTRACT FROM AUTHOR]

Electronic skins (E‐skins) capable of biomechanical/bioelectrical signal acquisition are intensively pursued for human‐centered healthcare of daily life. For practical use, it is highly desired, yet challenging, to mass‐produce E‐skins that are soft and breathable for wearing comfort, skin‐adhesive for robust signal acquisition, multi‐signal sensing for enhanced healthcare data. Herein, a scalable fabrication strategy for a bioinspired E‐skin (SPRABE‐skin) with a multi‐layered architecture is reported that integrates skin‐like softness, self‐protection, self‐adhesion, breathability, and bimodal sensing in a single patch. The fibrous thermoplastic polyurethane (TPU) scaffold endows the SPRABE‐skin with tissue‐like softness (Young's modulus of 3.36 MPa) and stretchability, good permeability to water vapor, and self‐protection against adverse loading events. A strain sensing layer composed of MXene‐carbon nanotubes@TPU (MXene‐CNT@TPU) composition exhibits ultra‐high sensitivity in a wide sensing range (gauge factor at strain of 485% reaches 63 494). An electrode layer made of MXene‐waterborne polyurethane (MXene‐WPU) provides a highly adhesive electrode‐skin interface, which enables the acquisition of biopotentials, such as electrocardiograph (ECG), electromyograph (EMG), electroencephalo‐graph (EEG), with improved fidelity even under various dynamic interferences. Finally, a SPRABE‐skin based human‐centered healthcare system is demonstrated that realizes the wireless, long‐duration, and dynamic monitoring of ECG and running activities. [ABSTRACT FROM AUTHOR]

Temperature‐independent properties are critical for high‐temperature thin‐film strain gauges (TFSGs). In this study, by controlling the electron scattering and tunneling effects in the TiB2/SiCN composites, the environmental interference of temperature fluctuations is successfully eliminated, and a temperature‐independent TFSG is fabricated. The effects of pyrolysis temperature and TiB2 content on the microstructural evolution and electrical properties of the ceramic films are studied. The temperature insensitivity is mainly attributed to the balance between the intrasheet resistance with a positive temperature coefficient of resistance (TCR) and the intersheet resistance with a negative TCR. This composite shows nearly constant resistance values over an ultrawide temperature range of 300–700 °C, with less than 0.05% deviation of the normalized resistance and TCR values as low as 1.6 ppm °C−1. In addition, the TiB2/SiCN films exhibited stable piezoresistive responses, with a gauge factor of 4.28, and the temperature‐independent strain response in the high‐temperature range is verified. [ABSTRACT FROM AUTHOR]

The quality of strain measurements using distributed fiber optic sensors (DFOS) depends largely on the bond between the host material and the optical fiber. Experimental investigations were carried out to test the suitability of five different DFOS types for crack monitoring. The DFOS were subsequently bonded to two 4 m long reinforced concrete (RC) beams, so that the influence of the application technique could be evaluated. DFOS measurements were verified by digital image correlation (DIC) and electrical strain gauges (SGs). For the different DFOS types, clear differences in the measured strain curves and determined crack widths were observed. The focus was on two robust DFOS, which can be deployed on construction sites. Compared to the layered sensing cable, a monolithic DFOS showed a clear strain distribution with pronounced strain peaks even for closely spaced cracks. The crack widths obtained by integrating the strain curves showed high agreement with DIC measurements. [ABSTRACT FROM AUTHOR]

Fatigue calculations of steel bridges are particularly vulnerable to inaccuracies in stress assessment. Their accurate evaluation ensures structural safety and can contribute to extending the remaining service life of many structures. The following study deals with the incorporation of measured data into fatigue assessment based on FE calculations using the trains operating on site. The bridge under study was equipped with a large number of strain gauges to capture the global and local effects of train passages. In addition, some strain gauges were placed on both rails to determine train speeds and axle forces. A detailed finite element model of the bridge was created and the strains caused by selected detected trains were blindly compared with measured values. Although a fairly good agreement was obtained for most strain gauges without the need for model updating, some sensors did not comply with the measured values. In order to achieve better agreement, a model update was performed. The authors concluded with a comparison of the original and updated models and the determined operating trains with regard to the fatigue calculations and discussed the added value. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) is crucial for ensuring operational safety in applications like pipelines, tanks, aircraft, ships, and vehicles. Traditional embedded sensors have limitations due to expense and potential structural damage. A novel technology using radio frequency identification devices (RFID) offers wireless transmission of highly sensitive strain measurement data. The system features a thin, flexible sensor based on an inductance‐capacitance (LC) circuit with a parallel‐plate capacitance sensing unit. By incorporating tailored cracks in the capacitor electrodes, the sensor's capacitor electrodes become highly piezoresistive, modifying electromagnetic wave penetration. This unconventional change in capacitance shifts the resonance frequency, resulting in a wireless strain sensor with a gauge factor of 50 for strains under 1%. The frequency shift is passively detected through an external readout system using simple frequency sweeping. This wire‐free, power‐free design allows easy integration into composites without compromising structural integrity. Experimental results demonstrate the cracked wireless strain sensor's ability to detect small strains within composites. This technology offers a cost‐effective, non‐destructive solution for accurate structural health monitoring. [ABSTRACT FROM AUTHOR]

Nonlinear continuum finite element (CFE) analyses rely on accurate multiaxial constitutive law formulations along with reliable imperfection patterns for simulating nonlinear geometric instabilities in steel members under mechanical loading. Validations of these models usually rely on conventional measurements of macroscopic parameters (e.g., displacement and strain field). It is common to use global deformation characteristics (e.g., deduced moment versus chord rotation) for model validation purposes of steel members exhibiting inelastic cyclic local buckling. The reason is that measurements from conventional strain gauge readings are not deemed to be reliable well before the onset of local buckling. This is potentially problematic when the accurate prediction of local strain demands is essential. This paper discusses the experimental results from a steel beam instrumented with a digital image correlation (DIC) system and how optical measurements acquired from DIC can be used to benchmark a CFE model representation of this beam. It is shown that while different CFE model types simulate accurately the moment rotation relationship of the steel beam, local strain demand predictions could vary considerably between model types. The results suggest that DIC measurements can inform the selection of proper imperfection patterns to be used in CFE models for the reliable estimation of inelastic strain demands. [ABSTRACT FROM AUTHOR]

Aluminium provides many advantages as a construction material in civil engineering, such as for example light weight, functionality by extruded profiles and corrosion resistance. It is obvious to use these advantages also for trusses. However, most aluminium alloys develop zones of weakening due to welding. The so called heat affected zones (HAZ) reduce the load‐bearing capacity of welded aluminium joints by up to 50%. Consequently, the design and execution of welded X‐joints within lattice girders are challenging. Indeed, the design of welded aluminium X‐joints is not specifically treated in EN 1999. Until now, the calculation of aluminium welded X‐joints relies on the steel standard EN 1993‐1‐8, which does not take into account the characteristic of aluminium. This results in errors and inefficient design. Thus, in this experimental research project the behavior of welded X‐joints in real‐scale models is explored. To this purpose, tests have been carried out on lattice girders made from aluminium alloy EN AW 6082 T6. In total, six girders with varying coefficient β and shape of the hollow section of brace members have been investigated. Thereby, the girders were loaded vertically until the failure of the X‐joints. Strains at the brace and chord members were measured by strain gauges and respective stresses were derived. In addition, a comparative analysis between experimentally and theoretically ‐ based on Eurocodes (EN 1993 part 1‐8 and EN 1999 part 1‐1) ‐ obtained results has been made. The analysis shows that the reduction of the load‐bearing capacity of welded aluminium X‐joints due to the HAZ is not constant but varies with the value of coefficient β and the shape of the cross‐section of the brace member. Obviously, the design of welded aluminium X‐joints based on EN 1993‐1‐8 applying a constant value for the HAZ does not reflect the true behavior of these joints as it leads to a quite conservative design approach. [ABSTRACT FROM AUTHOR]

An emergent direct‐write approach, aerosol‐jet printing (AJP), is gaining attention for the deployment of rapid and affordable microadditively manufactured energy‐efficient sensors and printed electronics. AJP enables a broad range of ink viscosities (0.001–1 Pa s) for printing diverse materials ranging from ceramics and metals to polymers and biological matter. Reproducible, high‐spatial‐resolution features (≈10 µm), and wide standoff distances (1–11 mm) between the nozzle and the substrate facilitate conformal printing of complex geometrical designs on nonplanar—e.g., stepped or curved—surfaces. This paper aims to provide a comprehensive overview of state‐of‐the‐art AJP‐based sensors (e.g., strain and temperature gauges, biosensors, photosensors, humidity and surface acoustic wave sensors, dielectric elastomer actuators, and motion, smoke, and hazardous gas detectors) and to discuss prospective applications. The drive toward cost‐effective devices that are smaller, lighter, and better‐performing remains a frontier challenge in the field of printed electronics. Consequently, as AJP becomes increasingly utilized in the high‐volume manufacturing of miniaturized active and passive sensors, it opens a pathway for facile large‐scale fabrication of devices for a wide range of consumer and industrial applications, including transportation, agriculture, infrastructure, aerospace, national defense, and healthcare. [ABSTRACT FROM AUTHOR]

Changes towards electrified vehicles lead to an overall increase of loads in chassis components, particularly in wheel attachments. Especially wheel attachments are facing increased dynamic loads, caused by increased axle loads, wheel dimensions, cornering loads due to tire grip and center of gravity improvements...to name some examples. To prevent fastener failures in future, new measurement and analysis procedures are being presented, enabling a complete and accurate verification of superimposed dynamic stresses caused by dynamic axial and bending loads in wheel & chassis fasteners at its critical failure area. Furthermore load‐specific S−N‐curves are required to accomplish an appropriate damage accumulation. This detailed understanding of loads occurring at fasteners itselfs enables improved safety in all chassis fasteners, provided these loads are known and taken into account at an early stage of a development process. [ABSTRACT FROM AUTHOR]

Background/Aim: Mouthguards (MTG) are used to prevent dental trauma. However, their protective effect on esthetic restorations and whether modified MTGs are beneficial is uncertain. The aim of this study was to evaluate the effect of hard inserts and air spaces in MTGs in protecting direct resin composite veneers during impact. Materials and Methods: Twenty resin composite veneers (1.0 mm) were prepared on upper right central incisors on printed maxilla models using polyether. The effect of the MTGs was evaluated in four groups (n = 5): Con‐MTG, conventional custom‐fit MTGs made with two layers of ethylene vinyl acetate (EVA); Air‐MTG, MTGs with the insertion of 2.0 mm air space between the two layers of EVA and tooth surface; PETG‐MTG, MTGs with 1.0 mm of polyethylene terephthalate glycol‐modified (PETG) inserted between the EVA layers; and No‐MTG, comprising resin composite veneers without MTG. The printed models were fixed in a pendulum device, and the impact was performed at 30°. The strain (μS) and shock absorption (%) of the MTG were recorded using strain gauges. Failure modes and cracks were evaluated using macro photography and transillumination and analyzed using the chi‐square test. Strain and shock absorption data were analyzed using the one‐way analysis of variance followed by Tukey's test (α = 0.05). Results: Mouthguards reduced strain and enhanced shock absorption, regardless of the MTG type (p <.001). Con‐MTG, Air‐MTG, and PETG‐MTG had shock absorption rates of 76.1%, 72.3%, and 33.4%, respectively (p <.001). The single No‐MTG model had a root fracture, while all the others had superficial damage. None of the MTG models had cracks or fractures. Conclusions: Mouthguards protected the resin composite veneers. The Con‐MTG and Air‐MTG groups had lower strain and greater shock absorption than the PETG‐MTG. Resin veneers had no cracks or damage following MTG use. However, 80% of the veneers had surface damage when no MTG was used. [ABSTRACT FROM AUTHOR]

Soft strain gauges provide a flexible and versatile alternative to traditional rigid and inextensible gauges, overcoming issues such as impedance mismatch, the limited sensing range, and fatigue/fracture. Although several materials and structural designs are used to fabricate soft strain gauges, achieving multi‐functionality for applications remains a significant challenge. Herein, a mechanically interlocked gel–elastomer hybrid material is exploited for soft strain gauge. Such a material design provides exceptional fracture energy of 59.6 kJ m−2 and a fatigue threshold of 3300 J m−2, along with impressive strength and stretchability. The hybrid material electrode possesses excellent sensing performances under both static and dynamic loading conditions. It boasts a tiny detection limit of 0.05% strain, ultrafast time resolution of 0.495 ms, and high linearity. This hybrid material electrode can accurately detect full‐range human‐related frequency vibrations ranging from 0.5 to 1000 Hz, enabling the measurement of physiological parameters. Additionally, the patterned soft strain gauge, created through lithography, demonstrates superior signal–noise rate and electromechanical robustness against deformation. By integrating a multiple‐channel device, an intelligent motion detection system is developed, which can classify six typical human body movements with the assistance of machine learning. This innovation is expected to drive advancements in wearable device technology. [ABSTRACT FROM AUTHOR]

In this article, a novel experimental device that combines bending and shearing was proposed to investigate the load‐bearing performance of large‐size C‐beam structures against bending‐shear buckling, allowing for the adjustment of bending‐shearing ratio. Three different bending‐shear coupling conditions were performed for test loading, and the strain gauges were carried out to detect the strain distribution for postbuckling performance of the large‐size C‐beam. The finite element models were established by ABAQUS/Explicit to explore the stress distribution and damage evolution during postbuckling failure. Thereafter, the LaRC05 and Hashin criterion was used for failure prediction of the large‐size C‐beam in numerical simulations. The experiment results show that the large‐size C‐beam has excellent postbuckling bearing capacity regardless of bending or shear resistance. Based on the results, the failure numerical model considering the stress distribution in postbuckling and the finite element calculation were in good agreement with experiments. This study can offer a practical reference for the postbuckling performance of large‐size C‐beam structures after bending‐shear coupling. [ABSTRACT FROM AUTHOR]

A structure with rocking mechanism is able to prolong the period of vibration and reduce seismic internal force. Recent research demonstrated the effectiveness of a tendon made of superelastic material wire connected in series with steel wire in controlling the amount of rotation and providing a source of hysteretic energy dissipation, thereby lowering the risk of overturning to a rigid structure undergoing whole‐body rotation. This article proposed to extend the use of superelastic tendon restraint on a (flexible) shear frame to strike a balance between the need to reduce the seismic force demand and the need to exercise control of the overturning risk. Initially, an analytical model for the rocking response of shear frame with the superelastic tendon restraint was developed. In addition, a physical model of the shear frame with tendon restraint was fabricated and tested under base excitations. Analysis results showed to match with experiment on both strain gauge and rotation sensor readings in the dynamic testing. Simulations and tests were also applied to an unrestrained shear frame for comparison. It was also found that the total deflection of the shear frame during the rocking phase could be described as horizontal vibration about a non‐constant balancing deflection. The analytical models developed for flexible rocking systems were extended in the current study to deal with superelastic tendon restrained rocking shear frames. The validity and versatility were confirmed by shaker table test results. [ABSTRACT FROM AUTHOR]

This paper analyzes the design of the down border of the flexible OLED display, and studies the influence of the neutral layer and the sensitivity of SD strain of different stacks of Pad Bending in the narrow border area based on the finite element simulation. The neutral layer is located in the PI2 layer, and the order of the strain sensitivity of SD at Bending edge is MCL>Organic layer>PI1>PI2, MCL thickness has the greatest influence on SD strain. Through the stacking optimization design based on the sensitivity analysis results, the SD strain is reduced from 11.1% to 6.6%. Finally realize the industry's smallest R0.1mm Pad Bending design. Based on bending strain gauge and 25N static push test, SD strain is at a safe level and pass more than 50 times push tests. Narrow border products with R0.1mm Pad Bending can pass various environmental reliability tests to meet the environmental requirements of terminal products. [ABSTRACT FROM AUTHOR]

Fiber Bragg Grating (FBG) sensors possess enormous potential for the cure monitoring and integrity assessment of Carbon Fiber Reinforced Polymer (CFRP) composites. These sensors can be embedded inside the structure to monitor the strain in the desired region of interest. The strain on an FBG sensor can be calculated by measuring the change in the center wavelength of the sensor. This change in center wavelength is a function of temperature and mechanical strain. Therefore, temperature compensation is necessary for a precise mechanical strain measurement with an FBG sensor. In this study, FBG sensors are embedded in different layers of the CFRP laminate to record the mechanical strain caused by the thermal expansion, which happens under the influence of temperature. Classical laminate theory (CLT) is implemented to assess the accuracy of FBG sensor measurements and the strain data acquired from both FBG sensor and CLT correlates. Furthermore, a resistive strain gauge is deployed to measure the strain under the influence of temperature. It is depicted that strain values recorded by the strain gauge under the influence of the temperature do not agree with the strain measured by CLT, and an error of 150% occurs among their values. [ABSTRACT FROM AUTHOR]

Objectives: Morphological variation in cranial sutures is used to infer aspects of primate feeding behavior, including diet, but strain regimes across sutures are not well documented. Our aim is to test hypotheses about sagittal suture morphology, strain regime, feeding behavior, and muscle activity relationships in robust Sapajus and gracile Cebus capuchin primates. Materials and Methods: Morphometrics of sinuosity in three regions of the sagittal suture were compared among museum specimens of Sapajus and Cebus, as well as in robust and gracile lab specimens. In vivo strains and bilateral electromyographic (EMG) activity were recorded from these regions in the temporalis muscles of capuchin primates while they fed on mechanically‐varying foods. Results: Sapajus and the anterior suture region exhibited greater sinuosity than Cebus and posterior regions. In vivo data reveal minor differences in strain regime between robust and gracile phenotypes but show higher strain magnitudes in the middle suture region and higher tensile strains anteriorly. After gage location, feeding behavior has the most consistent and strongest impact on strain regime in the sagittal suture. Strain in the anterior suture has a high tension to compression ratio compared to the posterior region, especially during forceful biting in the robust Sapajus‐like individual. Discussion: Sagittal suture complexity in robust capuchins likely reflects feeding behaviors associated with mechanically challenging foods. Sutural strain regimes in other anthropoid primates may also be affected by activity in feeding muscles. [ABSTRACT FROM AUTHOR]

Fluids are pervasive in the Earth's crust and saturate fractures and faults. The combination of fluids and gouge layers developing along faults can generate fluids of different viscosities. Such viscous fluids were found to influence the reactivation, frictional stability of faults, and eventually the dynamics of propagating earthquake ruptures. We reproduced laboratory earthquakes on analog material (PMMA) to study the influence of viscous lubricant on fault frictional stability, rupture nucleation, and propagation under mixed lubrication conditions. Experiments were conducted in dry conditions, and with fluids presenting a viscosity ranging from 1 to 1,000 mPa.s. Through photoelasticity, high‐frequency strain gauge sensors, and accelerometer measurements, we obtained new insights about the influence of lubricant on a characteristic nucleation length, rupture propagation velocity, and local slip and slip rate evolution during the reproduced frictional ruptures. Our experiments show that the presence of a lubricant generating mixed lubricated conditions along the fault induces, (a) a reduction of the frictional resistance, (b) an increase in nucleation length, (c) a decrease in the fracture energy. In addition, the larger the viscosity of the fluids, the larger the reduction of frictional strength and the increase in the nucleation length. Moreover, ruptures occurring under mixed lubricated conditions showed a pulse‐like rather than crack‐like behavior, suggesting that viscous lubrication can induce the transition from crack‐like to pulse‐like rupture along natural faults. We demonstrate, supported by existing theory, that this transition is mainly governed by the stress acting on the fault at the onset of nucleation, which is drastically reduced in presence of a lubricant. Plain Language Summary: Fluids naturally permeating the Earth's crust or being injected for reservoir stimulation can promote fault reactivation, resulting in natural or so‐called induced earthquakes. It is important to comprehend how the presence of these fluids, as well as their properties, affect the activation and magnitude of seismic events. In particular, we investigated the role of fluid viscosity under controlled experimental conditions through laboratory experiments on analog material. We show that for the same applied normal stress, faults under lubricated conditions (i.e., where a thin film of viscous lubricant had been spread) can be activated at much lower shear stresses than dry faults. At the same time, the generated events will be much smaller in magnitude (i.e., smaller stress drop) and propagate more stably. Key Points: Frictional strength of lubricated artificial interfaces is dramatically reduced under mixed lubrication conditionsNucleation length of rupture under lubricated conditions is larger than the one of ruptures under dry conditionsViscous lubrication (under mixed conditions) can affect the nature of ruptures that would propagated pulse‐like rather than crack‐like [ABSTRACT FROM AUTHOR]

Aseismic slip may occur during a long preparatory phase preceding earthquakes, and what controls it remains poorly understood. In this study, we explored the role of load point velocity and surface roughness on slow slip during the preparatory stage prior to stick‐slip events. To that end, we conducted displacement‐rate controlled friction experiments by imposing varying load point velocities on sawcut granite samples with different surface roughness at a confining pressure of 35 MPa. We measured the average slip along the fault with the recorded far‐field displacements and strain changes, while acoustic emission sensors and local strain gages were used to capture local slip variations. We found that the average amount of aseismic slip during the preparatory stage increases with roughness, whereas precursory slip duration decreases with increased load point velocity. These results reveal a complex slip pattern on rough faults which leads to dynamic ruptures at high load point velocities. Plain Language Summary: Earthquakes occur mostly along preexisting faults in the earth crust. These faults exhibit various geometrical complexities and are subjected to different strain rates. In the laboratory, we produce earthquake analogs by sliding sawcut granite blocks. We vary the geometrical complexity of the faults by roughening their surfaces and modify the strain rate by displacing the blocks at varying velocities. Under these different conditions, we measure how the forces accumulated by friction are released, by measuring stresses and displacements applied on the block's edges, using local strain deformation sensors, and by recording very small earthquakes occurring during sliding along the sawcut faults. We find that smooth sawcut faults tend to release all the energy accumulated very abruptly, after a very small amount of slip, regardless of the load point velocity applied. The processes leading to failure in the case of a rough fault are much more complex, involving a large amount of slip, and numerous small earthquakes which are distributed heterogeneously in space and time. Key Points: Acoustic emissions highlight the complex preparatory phase prior stick‐slips on rough faultsPreparatory slip increases with roughness and the duration of the preparatory phase decreases with increasing load point velocityRough and heterogeneous faults are more stable than smooth faults, but can become unstable with a small increase of load point velocity [ABSTRACT FROM AUTHOR]

Directional strain sensing is essential for advanced sensor applications in the field of human‐machine interfaces and healthcare. Here, the angle dependent anisotropic strain sensitivity caused by charge carriers percolating through cross‐linked gold nanoparticle (GNP) networks is studied and these versatile materials are used for the fabrication of wearable triaxial pulse and gesture sensors. More specifically, the anisotropic response of 1,9‐nonanedithiol cross‐linked GNP films is separated into geometric and piezoresistive contributions by fitting the measured data with an analytic model. Hereby, piezoresistive coefficients of g11 ∼ 32 and g12 ∼ 21 are extracted, indicating a slightly anisotropic response behavior of the GNP‐based material. To use the material for healthcare applications, arrangements of three GNP transducers are patterned lithographically and fully embedded into a highly flexible silicone polymer (Dragon Skin 30). The new encapsulation method ensures good and robust electrical contacts and enables facile handling and protection from external influences. A facile read‐out with wireless data transmission using off‐the‐shelf electrical components underlines the great potential of these devices for applications as skin‐wearable healthcare sensors. [ABSTRACT FROM AUTHOR]

The fatigue of concrete has been the subject of research for many years, and yet, there are still open questions. In particular, the fatigue‐induced damage evolution accompanied by a stress redistribution process propagating through the concrete structure is still not fully understood. So far, there are only few experimental studies addressing the fatigue propagation through a material zone occurring, for example, in beams with a pulsating, nonuniform stress profile. To investigate the influence of such stress configurations on the material and structural degradation process, a measuring concept has been developed combining digital image correlation, fiber optic sensors, and conventional strain gauges. The presented experiments visualize the propagating fatigue degradation in the compression zone of prestressed concrete beams subjected to fatigue loading. Based on the developed measurement concept, the quantitative foundation for a comprehensive validation of design rules and material models accounting for concrete fatigue can be significantly extended. Highlights: Design of a test setup for the analysis of compressive fatigue propagation in concreteEvaluation of a coordinated monitoring concept combining various measurement techniquesVisualization of the propagating fatigue degradation of prestressed concrete beams [ABSTRACT FROM AUTHOR]

Aeroelastic parked testing of a unique downwind two‐bladed subscale rotor was completed to characterize the response of an extreme‐scale 13‐MW turbine in high‐wind parked conditions. A 20% geometric scaling was used resulting in scaled 20‐m‐long blades, whose structural and stiffness properties were designed using aeroelastic scaling to replicate the nondimensional structural aeroelastic deflections and dynamics that would occur for a lightweight, downwind 13‐MW rotor. The subscale rotor was mounted and field tested on the two‐bladed Controls Advanced Research Turbine (CART2) at the National Renewable Energy Laboratory's Flatiron Campus (NREL FC). The parked testing of these highly flexible blades included both pitch‐to‐run and pitch‐to‐feather configurations with the blades in the horizontal braked orientation. The collected experimental data includes the unsteady flapwise root bending moments and tip deflections as a function of inflow wind conditions. The bending moments are based on strain gauges located in the root section, whereas the tip deflections are captured by a video camera on the hub of the turbine pointed toward the tip of the blade. The experimental results are compared against computational predictions generated by FAST, a wind turbine simulation software, for the subscale and full‐scale models with consistent unsteady wind fields. FAST reasonably predicted the bending moments and deflections of the experimental data in terms of both the mean and standard deviations. These results demonstrate the efficacy of the first such aeroelastically scaled turbine test and demonstrate that a highly flexible lightweight downwind coned rotor can be designed to withstand extreme loads in parked conditions. [ABSTRACT FROM AUTHOR]

We conducted fluid injection experiments on cylindrical low‐permeability granite samples with a critically stressed sawcut fault at local injection rates of 0.2 and 0.8 mL/min and confining pressures of 31 and 61 MPa. A local array of six strain gauges attached close to the faults allows us to estimate the nucleation length of each injection‐induced dynamic slip event (i.e., laboratory earthquake). We find nucleation lengths decrease from approximately 90% to <15% of the fault length with higher injection rate and increased effective normal stress. Injection‐induced laboratory earthquakes with smaller nucleation lengths show generally higher peak slip rates and larger fault slip displacements, signifying an intensified seismic hazard. Our results also indicate that initially stable fault patches may be reactivated to slip seismically by increasing injection rates. This study systematically demonstrates that higher injection rates constitute dynamic loading, which increase the seismic hazard by shrinking the earthquake nucleation length. Plain Language Summary: Earthquakes associated with fluid injection in various geo‐energy settings, such as shale gas and deep geothermal energy, have shelved many projects with great potential. However, the injection‐rate dependence of earthquake nucleation length, which characterizes the length of a slowly slipping (creeping) fault patch in preparation for a subsequent earthquake, remains to be studied. To this end, we performed fluid injection experiments on low‐permeability granite samples containing a critically stressed sawcut fault. We demonstrate that the nucleation length of injection‐induced laboratory earthquakes shrinks with higher effective normal stress and larger injection rate. We show that laboratory earthquakes induced by higher fluid injection rates are characterized by smaller nucleation lengths, faster peak slip rates, and larger fault slip displacements. Our results also suggest that a stable fault patch subject to low‐rate injection may be induced to slip seismically by increasing injection rates. Our findings may explain the higher seismic hazards associated with higher injection rates as has been frequently documented in field cases. Key Points: The nucleation length of injection‐induced laboratory earthquakes reduces with higher injection rate and greater effective normal stressInjection‐induced laboratory earthquakes with smaller nucleation lengths exhibit higher peak slip rates and larger fault slip displacementsFast‐rate fluid injection may cause initially stable fault patches of smaller sizes to slip seismically, leading to higher seismic hazards [ABSTRACT FROM AUTHOR]

Background: Artificial organs are playing an increasingly important role in medical field. Artificial anal sphincter, as an example, is a widely used medical device for fecal incontinence. Though it could help patients maintain continence, the issue of perception reconstruction is still unsolved, which means that patients cannot control defecation as desired. Methods: In this paper, a novel sensor system based on vector similarity has been analyzed and evaluated. The sensor system is a self‐packaged strain gauge sensor with a small size 14.5 mm × 6 mm, especially for medical device implanted in body to reconstruct perception function. In order to overcome the disadvantages of single threshold judgment, a more accurate and reliable judgment standard for content pressure detection in rectum is developed by using vector similarity method. Therefore, in the novel sensor system, standard multi‐parameters are comprehensive considered. Furthermore, weight‐optimization of sensors are investigated since each sensor has played a different role in detection. Finally, sensor calibration, in vitro and in vivo experiments are established. Results: In sensor calibration, the result R2 > 0.99 presents the strain gauge pressure sensor has a good linearity. After that, a series of in vitro experiments have been conducted. The optimized sensor system shows a high accuracy rate in perception reconstruction, which is 87.5% on early warning and 95% on the alarm. In the following in vivo experiments. The results indicate that the average accuracy of the proposed perception reconstruction module has increased by 17.7%, compared with that without optimized sensor system. Conclusions: All of these have proven that the novel perception reconstruction module with sensor system based on vector similarity is more acceptable and reliable. [ABSTRACT FROM AUTHOR]

Conventional strain gauges are not designed for accurate measurement over the large range of deformations possible in compliant textiles. The thin, lightweight, and flexible nature of textiles also makes it challenging to attach strain gauges in a way that does not affect the mechanical properties. In this manuscript, soft, highly extensible fibers that propagate light (i.e., stretchable lightguides) are stitched as a strain gauge to map the deformation of a nylon parachute textile under tension. When under load, these fiber optic strain gauges propagate less light, and this strain‐induced light modulation is used to accurately (absolute error≈2.93%; Std. Dev.: 3.02%) measure strain in the <30% range before these textiles fail. This system has directionality; strain in parallel to the sensor results in little light attenuation while perpendicular loading shows high sensitivity (Gauge factor⊥≈24.8 and Gauge factor||≈0.05 at the first 1% strain). Structural and optical simulations are coupled to demonstrate that load transfer on the fiber optic by the stitchwork is the dominating cause of signal modulation. To further validate the hypotheses, digital image correlation was used under dynamic loading conditions to show that these sensors do not significantly affect the mechanical properties. [ABSTRACT FROM AUTHOR]

Hydrogel‐based sensors with excellent flexibility and stretchability have received extensive attention. However, fabricating anti‐freezing, high‐strength, and conductive hydrogel‐based sensors remains a significant challenge. A stretchable sensor with high strength and anti‐freezing herein is constructed using poly(vinyl alcohol)/urea (PVA/urea) ionic hydrogels. The PVA/urea ionic hydrogels were prepared by a simple strategy of soaking the freeze–thawed PVA hydrogels in sodium citrate (Na3Cit) water/urea aqueous solutions. The presence of Na3Cit in the hydrogel produces hydrophobic aggregation, endowing the PVA/urea ionic hydrogel with high mechanical properties (~1.51 MPa) and makes the hydrogel have high strain gauge factors (GF = 1.94). The synergistic effect of Na3Cit and urea endows the PVA/urea ionic hydrogel with anti‐freezing properties (~−20°C). The obtained sensors have excellent stability (100 cycles at ε = 85%) and could detect various human activities even at −20°C. More importantly, joint motion can be monitored wirelessly via Bluetooth at −20°C. This work provides a feasible method to construct anti‐freezing, high‐strength, and conductive hydrogel. It paves the way for versatile applications in human‐motion detection, intelligence device, and biomimetic skin. [ABSTRACT FROM AUTHOR]

Mechanical characterization of cells is important for understanding their behavior. This paper reports on an in situ evaluation of the stiffness of cellular spheroids using a pinching device. The pinching device is integrated with a bimorph piezoactuator and strain gauge. It can pinch an object by combining a piezo bimorph actuator and a thin Si structure and can detect the reaction force from an elastic object using a strain gauge integrated into the thin Si structure. The strain gauge can detect the bending deformation of the device and estimate the reaction force by considering actuation. This paper presents the design of the pinching device and experimental results when used for the in situ evaluation of the stiffness of cellular spheroids. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Liquid‐metal (LM)‐based soft and stretchable electronics (SSEs) provide unique advantages for wearable computing, soft robotics, and implantable devices applications involving physical interaction with biological tissues and delicate objects. However, the lack of scalable manufacturing techniques prevents their mainstream adoption and commercialization. This paper introduces a scalable and reproducible manufacturing technique for wafer‐level fabrication of LM‐based SSEs, including LM‐only devices and hybrid circuits with LM and solid‐state microelectronics. The approach combines selective metal‐alloy wetting (SMAW) and controlled dip‐coating of eutectic gallium‐indium (EGaIn). The alloying of EGaIn and metal enables depositing EGaIn selectively onto the circuit layout defined by lithographically patterned copper traces on elastomer‐coated wafers. An automated, wafer‐level dip‐coating (DC) approach is developed to enable controllable and reproducible deposition of EGaIn. Wafer‐level simultaneous fabrication of many LM capacitors is demonstrated, and their geometric and electrical reproducibility is evaluated. The results indicate that the SMAW‐DC process can fabricate LM circuits reproducibly and rapidly. Hybrid SSEs are demonstrated by fabricating multiple wearable patches of ultra‐high frequency circuits with an LM dipole antenna, an LM strain gauge, and a solid‐state temperature sensor. Importantly, the presented technique can be integrated into the standard microfabrication flow for microelectronics, ensuring a high level of scalability. [ABSTRACT FROM AUTHOR]

Structural Health Monitoring (SHM) is a technology aimed to monitor the soundness of the structures. Applications for aircraft structure are largely investigated. The goal is to utilize the information acquired during the monitoring to save maintenance costs, improve flight safety, and design lighter structures. There are different issues investigated by SHM research, like load monitoring and impact detection. The most primarily investigated issue is damage detection, that is, developing a system that utilizes sensors to detect the damages in the structure. The damage detection can be performed with two different types of sensors: dynamic and static sensors. Dynamic sensors work by the transmission of waves through the structures. Defects are identified by deviation and reflection of the waves by damages. The SHM approach described in this work uses static sensors, like strain gages or fiber optics. The strain fields under load in pristine and damaged conditions are compared; damages are identified by evaluating the change in the strain field. Developed and patented in Leonardo Aircraft, two different algorithms for damage detection are described in this work. The algorithms are based on reverse finite element model (F.E.M.) and neural networks. [ABSTRACT FROM AUTHOR]

Strain sensors with wide‐range stretchability, good sensitivity, high gauge factor, and reliability are needed for several applications. Herein, stretchable strain sensors capable of operating over multi‐strain range and having an excellent gauge factor are presented. The systematic study, carried out with different combinations of elastomer, conductive filler, and graphene–carbon paste (GCP), revealed that the sensors exhibit excellent stretchability when only filler particles are present in the elastomer, and they exhibit high sensitivity when filler particles are mixed with GCP. The molecular dynamics simulations show that the addition of GCP to the elastomer‐filler composite helps to attain an excellent sensor response with wide range stretchability. Thus, sensors' response can be tuned by using selected material composition. Accordingly, the strain sensor with 50 wt% GCP reveals 500% stretchability and a maximum gauge factor of 504. Likewise, 150 wt% GCP loading lead to sensors with 45% stretchability and an unprecedented gauge factor of 1 834 140. The capability to detect the small‐ to large‐scale strains makes the presented sensors attractive for monitoring the movements of body parts–which range from small movements during facial expression to large movement experienced by the limb joints. [ABSTRACT FROM AUTHOR]

A thermoplastic matrix composite flat panel stiffened by induction welded stringers, according to a typical aerospace configuration was tested. A Poly‐Ether‐Ether‐Ketone (PEEK) matrix reinforced by carbon fibers was adopted. The aim of this study was to investigate the shear buckling, a load condition that is very common for the aerospace structures, of the panel obtained using a non‐conventional approach for its fabrication, that is, induction welding. A finite element (FE) model capable to describe the buckling and the postbuckling behavior of the stiffened panel was also developed and compared with experimental results. Testing was performed using fixtures suitably designed to transmit a pure shear to the panel, and strain gauges were mounted on the external surfaces to measure the deformations. [ABSTRACT FROM AUTHOR]