Strain Mapping Research Articles

2-Dimensional strain mapping and post curing effects on viscoelastic properties of glass fiber infused photocurable composites prepared using Vat-photopolymerization process

2-Dimensional strain mapping and post curing effects on viscoelastic properties of glass fiber infused photocurable composites prepared using Vat-photopolymerization process

In Situ Scanning Electron Microscopy Crack Characterization and Resistance Evolution in Cyclically-Strained Ag Nanoflake-Based Inks.

The reliability of nanocomposite conductive inks under cyclic loading is the key to designing robust flexible electronics. Although resistance increases with cycling and models exist, the exact degradation mechanism is not well understood and is critical for developing inks. This study links cracking behavior to changes in electrical resistance by performing in situ cyclic stretch experiments in scanning electron microscopy (SEM) with synchronized resistance measurements. Two screen-printed conductive inks, PE874 and 5025, on thermoplastic polyurethane (TPU) and polyimide (PI) substrates, respectively, were tested using the in situ technique. The obtained SEM images were analyzed with digital image correlation (DIC) to map the strain across cycles. The strain maps show that fatigue damage mainly occurred within the cracks formed during the initial monotonic stretch. There was no delamination at the ink-substrate interface or crack extension along the surface with cycling. Instead, fatigue damage resulted from a combination of crack widening and local shearing within the existing cracks. Crack depth varied based on the ink and substrate properties. The cracks in the 5025 ink on the PI substrate were only partially through the ink thickness, while fully through-thickness cracks were more prevalent in the PE874 ink on the TPU substrate. The 5025 ink showed a faster resistance increase with cycling than the PE874 ink because fatigue damage affected more bridging ink material for partial through-thickness cracks. Higher strain amplitudes caused greater crack widening and shearing and therefore faster resistance increase per cycle.

The heartbeat induces local volumetric compression in the healthy human brain: a 7 T magnetic resonance imaging study on brain tissue pulsations.

Intracerebral blood volume changes along the cardiac cycle cause volumetric strain in brain tissue, measurable with displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging. Individual volumetric strain maps show compressing and expanding voxels, raising the question whether systolic compressions reflect a physiological phenomenon. In DENSE data from nine healthy volunteers, voxels were grouped into three clusters according to volumetric strain in a tissue mask excluding extracerebral blood vessels and cerebrospinal fluid using a two-stage clustering approach. To confirm the physiological source of the compressions, data from a patient with a cranial opening was analysed. Spatial patterns of compressing and expanding clusters were matched to high-resolution anatomical scans, acquired in one additional individual. All healthy subjects consistently showed a cluster with compressive volumetric strain during systole, covering 10.2% [7.3-13.1%] (mean [95% confidence interval]) of the tissue mask, besides two expansion clusters. In the patient, no compression was observed. Although the compression cluster did not consistently co-localize with intracerebral veins or perivascular spaces on the anatomical scans, the first-stage clustering results suggested that the distinction between the clusters has a (peri)vascular source. In conclusion, brain tissue shows heartbeat-induced volumetric compressions, possibly indicating compression of porous structures such as intracerebral veins or perivascular spaces.

Synchrotron X-Ray Micro Computed Tomography Investigation of in-Situ Deformation of PFSA Membranes for Water Electrolyzers

Proton exchange membrane water electrolysis (PEMWE) is an electrochemical energy conversion technology that splits water molecules to produce hydrogen gas. PEMWE, when powered by renewable electricity sources, offers a promising solution to generate clean hydrogen fuel as well as for storing energy [1]. One barrier to the wide-scale commercialization of PEMWEs is their durability, which is compromised in part by mechanical damage to the membrane. It has been hypothesized that the rough surface of the PTL causes damage to the surface of the membrane in the form of pinholes and interfacial fractures under PEMWE operating conditions, which lead to increased degradation of the membrane and reduced performance and longevity of the PEMWE cell [3]. Furthermore, the extent of damage and deformation to the membrane can be related to the morphology (i.e. the feature and pore size/distribution) of the PTL. Thus, characterizing the interfacial contact between the PEM-PTL and the stresses induced in the membrane during operation is of great importance for understanding and mitigating the mechanical aspects of failure in PEM electrolyzers.To investigate this phenomenon, we conducted X-ray micro computed tomography (MCT) at the advanced light source (ALS) at Lawrence Berkeley National Laboratory (LBNL) on a PTL/membrane stack being pressed together at 2.2, 4.4, 8.9, and 22.2 MPa using a custom compression stage. We tested the effect of two different standard PTL morphologies: a sintered Ti from Mott® and a fibrous Ti from Bekeart® on both wet and dry membrane specimens (Nafion 115). By carefully segmenting the X-ray MCT images, we were able to construct 3D strain mappings across the membrane to highlight areas of concentrated stress due to prominent features of the PTL protruding into the membrane and portions of membrane extruding into the pores of the PTL. Based on these results, we find that prominent features on the PTL surfaces lead to increased membrane surface roughness and strain, and indeed can pierce the hydrated membrane surface at elevated pressures. In summary, our study offers a unique insight into the deformation mechanisms that occur at the membrane surface as it interfaces with the PTL under standard PEMWE operating conditions of high compressive stress and hydrated states. This work will guide researchers within the PEMWE community to develop material and integration strategies that mitigate mechanical degradation and improve the system lifetime.

Boron Delta-Doping in Si : B Stacks By RP-CVD Epitaxy

To reach the electrical performance of advanced CMOS technology, the source and drain contact resistance becomes a key figure of merit. By reducing the size of electrical devices, the minimum active carrier concentration required to obtain sufficiently low contact resistance and high-performance increases. However, incorporation of dopants by Reduced Pressure-Chemical Vapor Deposition (RP-CVD) is limited to <1020at/cm3 (substitutional atoms). For high B2H6 flow ratio (F[B2H6]/F[H2] of 7.1x10-06 at 750 °C, 10 torr), the material either forms defects, notably Boron clusters [1], or even turns polycrystalline which increase the resistivity [2]. To incorporate as many electrically active dopants as possible while maintaining a good crystalline quality, stacks of Boron saturated layers δ-(B) in between each Si:B thin film, known in the literature as delta-doping, are investigated to further reduce resistivity without degrading the crystalline quality [3].In this presentation we show that the delta-doping method with the use of a stacked δ-(B)/Si:B structure, provides a factor two decrease of the resistivity limit and a ten times increase of electrically active B dopants as compared to a standard co-flow doping process. Such results are obtained for basic set of process parameters, with temperature and pressure set at 750 °C and 10 torr, respectively.The influence of the number of δ-(B) layers and of the saturation times (per δ-(B) layer) were investigated from 2 to 23 and from 20 s to 600 s respectively. The resistivity reduces when increasing the saturation time and the number of saturation steps up to a plateau at saturation times around 400 s, whatever the number of δ-(B) layers (Fig. 1). In standard growth conditions (DCS flux, Pressure and Temperature), and at low B2H6 flow ratio ( a record resistivity of 8.9x10-04 Ω.cm was obtained which is a decade lower than the 9x10-03 Ω.cm obtained with the standard co-flow process. Secondary Ion Mass Spectrometry (SIMS) analyses and High-Resolution Transmission Electron Microscopy (HRTEM) images were performed on different stacks (see Fig. 2a and 2b). SIMS profiles showed that the total [B] was about 2x1021 at.cm-3 compared to electrically active [B] of 1.5x1020 at.cm-3, meaning that only 10% of incorporated Boron was electrically active.Strain mapping analyses were performed on a stack with five δ-(B) layers. Despite the good crystalline quality and a low resistivity, the local strain mapping image revealed a dislocation associated to the high strain in the δ-(B) layers. In addition, the four hours required to process the epitaxial stack with the best resistivity result is prohibitive for industrial application.To achieve lower contact resistance, high B2H6 flow ratios (>1x10-06) were investigated. The saturation time and number of δ-(B) layers were kept constant at 5s and 20, respectively, to obtain similar results but with shorter, more industry orientated process times (~ 5 min). The resistivity and the total [B] did not reduce further compared to previous results (at lower B2H6/H2 flow ratio). However, the SIMS and the TEM revealed a more homogeneous boron distribution over the entire depth of the layer (see Fig.2c).The efficiency of the process, in terms of crystalline quality, was assessed for low and high B2H6/H2 flow ratios typically and >1x10-06 respectively using the soaking volume parameter (Vsoaking). It is defined as the product of B2H6 flow (in sccm) and flow time (in s) which gives the total volume of B2H6 introduced into the epitaxy chamber during a saturation step. Vsoaking initially evolves linearly up to 8x10-08 m-3 for low B2H6 flow and 2.5x10-08 m-3 for high B2H6 flow and then it saturates. At large Vsoaking, the crystalline quality degraded probably due to the strain in the δ-(B) which perturbates the crystal lattice. The results show that for the same amount of [B], the lower Vsoaking (1x10-7 m3), corresponding to the higher B2H6 flow process, lead to a higher crystalline quality.In conclusion, in standard experimental conditions, the delta doping process leads to a decade lower resistivity while preserving excellent crystalline quality when using high B2H6 flow and low exposure times.[1] Cristiano et al. / Appl. Phys. Lett., Vol. 83, No. 26, 29 December 2003[2] J.M. Hartmann et al. / Journal of Crystal Growth 264 (2004) 36-47[3] D. Kohen et al. / Journal of Crystal Growth 483 (2018) 285-290 Figure 1

In situ SEM analysis of cracking and its quantitative link to resistance evolution in uniaxially stretched nanocomposite inks

Nanocomposite conductive inks consisting of metal flakes embedded in a polymer binder are employed as interconnect materials in flexible hybrid electronics (FHE) devices. Crack formation has been hypothesized to play a key role in the ink's electrical degradation (increase of resistance), but the two have not been directly correlated. To address this gap, two classes of inks are studied using uniaxial stretch experiments, with in situ SEM imaging, and synchronous electrical resistance measurement. In plane strain maps obtained from digital image correlation (DIC) analysis of wide-field SEM images (∼300 μm in width) identify crack patterns at various applied strains. From these strain maps, crack length measurements are obtained. A finite-element based numerical model adapted for non-uniform crack lengths is used to predict normalized resistance increase from the crack lengths. The model predictions are compared against the experimentally measured resistance changes. There is a remarkable correlation between the predicted and experimentally measured normalized resistance values. The linear crack density was also used to help understand the relation between the effective crack length and resistance increase. Closeup images of the ink top surface and the ink cross-section during the in situ SEM stretch experiment are used to explain differences between predicted and measured normalized resistance.

Nanoscale mapping of local intrinsic strain-induced anomalous bandgap variations in WSe2 using selective-wavelength scanning photoconductivity microscopy

Nanoscale defects can locally tailor the optoelectronic properties of two-dimensional materials such as bandgap. However, it is still challenging to directly map and analyze the defect-induced bandgap variations in a quantitative manner. Here, we report the nanoscale mapping of local intrinsic strain-induced anomalous bandgap variations in as-grown WSe2 by using a selective-wavelength scanning photoconductivity microscopy. In this method, a conducting nanoprobe is utilized to map the spatial distributions of strain, sheet-conductance, and charge trap density (Neff) of epitaxially-grown WSe2 on sapphire while illuminating monochromatic light of selective wavelengths. Under un-illuminated conditions, the maps showed WSe2 domain structures with boundaries having slightly lower sheet-conductance and higher Neff than those in domains, presumably due to low misorientation angles between adjacent epitaxially-grown domains. By measuring wavelength-dependent photoconductance maps and fitting each pixel value of the maps, we could successfully obtain the map of local bandgap. The map clearly showed bandgap variations inside domains as well as rather low bandgaps at boundaries. By comparing with local strain map, we found that tensile strain effectively reduced bandgap following two different power-law relationships. Such anomalous bandgap variations in WSe2 could be explained by strain-induced weakening of d-orbital couplings. Furthermore, in a monolayer-bilayer WSe2 interface, bilayer WSe2 exhibited lower bandgap than the underlying monolayer WSe2, while interfacial boundaries exhibited the strain-induced bandgap values in between those of monolayer and bilayer WSe2. Since our method allows us to directly map the intrinsic strain-induced bandgap variations with a nanoscale resolution down to tens-of-nm, it can be a powerful tool for basic research and practical applications of optoelectronic devices based on two-dimensional materials.

Nanoscale Identification of Local Strain Effect on TMD Catalysis.

Strain engineering plays a crucial role in activating the basal plane of the TMD catalysts. However, experimental evidence linking strain strength to activity and distinguishing effects of compressive and tensile strain remains elusive due to the absence of high-resolution in situ correlation techniques. Here, we utilize nanobubble imaging by on-chip total-internal reflection microscopy to visualize active sites on the basal plane of strained MoS2 during hydrogen evolution reaction and atomic force microscopy to correlatively capture the nanoscale morphology and strain maps. By integrating the activity, morphology, and strain maps into comprehensive statistical analyses, we elucidate the strain effect on local activity at both multiprotrusion and (sub)single-protrusion levels. Our findings demonstrate that strain effectively activates sulfur vacancies on the basal plane, with tensile strain significantly enhancing local activity compared to compressive strain. Furthermore, we observe a time-dependent propagation of activity from high-activity to low-activity regions within single protrusions. This work clarifies the interplay between structural morphology and catalytic activity and provides new guidelines for the rational design of optimal TMD catalysts.

Microscopic Strain Mapping: Functional Diversity and Their Demands

Microscopic Strain Mapping: Functional Diversity and Their Demands

MULTIAXIAL AND UNIAXIAL FATIGUE ANALYSIS OF A MOORING CHAINS FOR AN OFFSHORE FLOATING WIND TURBINE

This paper presents the fatigue study (uniaxial fatigue and multiaxial fatigue) of mooring chains for a floating wind turbine (FWT). The operating principle of a floating offshore wind turbine (FOWT) and general information on uniaxial and multiaxial fatigue are presented, together with a reminder of the standards governing fatigue in the offshore sector. Uniaxial fatigue damage and service life calculations are carried out for various loading conditions and sea states. The finite element method is carried out using ANSYS software in order to estimate the best mapping of stresses and strains on the structure of the mooring chain. Finally, a simulation was also carried out using usingMatlab software to calculate the damage and multiaxial fatigue life. Comparison of the two analyses shows that uniaxial fatigue analysis minimises long-term damage and that multiaxial fatigue should be preferred for estimating the durability of offshore structures under extreme loading.

Speckle tracking echocardiography as a predictor of location of ablation sites in candidates to catheter ablation for recurrent ventricular tachycardia

Abstract Background Preoperative imaging is essential before a ventricular tachycardia (VT) ablation procedure, to improve operative outcomes and reduce procedural times. Although MRI is the gold standard, it has several limitations, including patient compliance, possible presence of non-MRI-compatible devices, and long acquisition time. Speckle tracking echocardiography (STE) is a reliable and appealing technique that quantifies regional and global myocardial deformation, as well as layer-specific (endo-, mid- and epicardial) longitudinal strain, without MRI limitations. Purpose This study aimed to evaluate the efficacy of STE in predicting VT ablation sites. Methods In this study, we compared the bull’s eye segmentation of the left ventricle, global and layer-specific, obtained with STE (TomTec Arena), to investigate whether echocardiography can predict the areas of scar and late potential, as identified by electroanatomic mapping (EnSite X mapping, HD Grid mapping catheter, Abbott). Strain analysis and electroanatomic mapping data were matched segment-by-segment to obtain pairs of endocardial strain and bipolar substrate maps, as well as pairs of midmyocardial/epicardial strain and unipolar substrate maps. Results Twenty-three consecutive patients with an indication for catheter ablation for recurrent VT were enrolled. All patients were being treated with beta-blockers, 52% were taking amiodarone, and only 2 patients were on mexiletine. A total of 1170 pairs of bull’s eye segments were available for analysis. A binary logistic mixed-effects model was used to predict the presence of electroanatomical scar based on strain echocardiography data, to account for interpatient variability. The study findings highlighted a close correlation between the bipolar map and endocardial strain values, and between the unipolar map and midmyocardial strain values. Progressively higher (less negative) values of endocardial strain proved predictive of bipolar electroanatomical scar, with an increase in the odds ratio of bipolar electroanatomical scar equal to 6.2% (95% confidence interval 2.5%-10%) for each unit increase in strain values. Similarly, progressively higher values of midmyocardial strain were predictive of unipolar electroanatomical scar, with an increase in the odds ratio of unipolar electroanatomical scar equal to 6.2% (95% confidence interval 1.2%-11.4%) for each unit increase in strain values. Conclusions The data from our study showed an anatomical correspondence between the areas of low potential identified by electroanatomical mapping and the areas of anomalous longitudinal strain. In particular, the endocardial strain correlates with the bipolar map, and the meso-epicardial strain correlates with the unipolar map. These data may prove useful in the appropriate planning of the procedure in patients with an indication for catheter ablation in the context of recurrent VT.

Association between objectively-measured sleep duration and early cardiac and hepatic imaging changes in adolescents: insights from the EnIGMA study

Abstract Introduction Inadequate sleep duration (SD) has been associated with adverse cardiovascular (CV) events in adults and adiposity in all life stages. Furthermore, previous cross-sectional studies have shown a possible association between self-reported SD and cardiac structural alterations as detected with echocardiography and cardiovascular magnetic resonance (MR), even in young healthy people. However, there is a lack of longitudinal studies demonstrating an association between objectively-measured SD and structural cardiac alterations. Purpose To assess the association between SD and MR-derived cardiac and hepatic parameters in adolescents. Methods This study used longitudinal data collected as part of the SI! Program for Secondary Schools trial in Spain (2017-2021), which enrolled 1326 participants (mean age: 12.5±0.5 years at baseline). Measurements were taken at three different time-points: baseline, 2-year follow-up and 4-year follow-up. SD and physical activity were assessed by accelerometry for seven consecutive days at each follow-up. The participants were offered to undergo a MR scan in the final follow-up as part of the Early imaging markers of unhealthy lifestyles in adolescents (EnIGMA) study. The imaging protocol included a cine SSFP to provide images for chamber size and function, myocardial tagging acquisitions to assess myocardial strain, T1 and T2 mapping sequences to provide precise myocardial relaxation time properties, and a liver mDixonQuant sequence to obtain liver fat content, using a 3-T scanner. The cumulative effect of the independent variable (SD) and the covariates was assessed using the area under the curve (AUC) method, calculating the integral of the curve parameters during the follow-up period for each subject. To facilitate interpretation, AUC values were divided by the years of follow-up. The participants were included in the analysis if they had available data for SD in at least 2 of the 3 time-points. The association between SD and the MR parameters was assessed by linear regression models. Results 109 participants (61 girls [56.0%]; mean age=16.0±0.5 years) were included in this study. Indexed left ventricular (LV) mass, as well as indexed end-diastolic biventricular volumes were higher in boys than in girls (Figure 1). SD AUC (hours/day) was independently and inversely associated with indexed LV mass and liver fat fraction in the unadjusted and adjusted (age, gender, physical activity, body mass index percentile, and systolic and diastolic blood pressure percentiles AUCs) models (Figure 2). There were no significant associations between the SD AUC and other MR-derived parameters. Conclusion Shorter SD is independently associated with initial stages of cardiac remodeling and liver fat accumulation as assessed with state-of-the-art MR as early as in adolescence. Considering these results, health promotion programs should be implemented early in life emphasizing the importance of good sleep habits.Participant characteristicsAssociation between SD and MR

Tailoring smart hydrogels through manipulation of heterogeneous subdomains

The mechanical interactions among integrated cellular structures in soft tissues dictate the mechanical behaviors and morphogenetic deformations observed in living organisms. However, replicating these multifaceted attributes in synthetic soft materials remains a challenge. In this work, we develop a smart hydrogel system featuring engineered stiff cellular patterns that induce strain-driven heterogeneous subdomains within the hydrogel film. These subdomains arise from the distinct mechanical responses of the pattern and film domains under applied mechanical forces. Unlike previous studies that incorporate reinforced inclusions into soft matrices to tailor material properties, our method manipulates the localization, integration, and interaction of these subdomain building blocks within the soft film. This enables extensive tuning of both local and global behaviors. Notably, we introduce a subdomain-interface mechanism that allows for the concurrent customization and decoupling of mechanical properties and shape transformations within a single material system—an achievement rarely accomplished with current synthetic soft materials. Additionally, our use of in-situ imaging characterizations, including full-field strain mapping via digital imaging correlation and reciprocal-space patterns through fast Fourier transform analysis of real-space pattern domains, provides rapid real-time monitoring tools to uncover the underlying principles governing tailored multiscale heterogeneities and intricate behaviors.

Enhanced strain mapping Unveils internal deformation dynamics in Silicon-based lithium-ion batteries during electrochemical cycling

Silicon-based anodes have emerged as a promising advancement in lithium-ion battery technology, offering significantly higher lithium storage capacities than traditional graphite. However, the volumetric expansion of silicon-anodes can swell by up to 300 % during lithiation-presents serious challenges to their structural integrity and electrochemical stability. This study investigates the internal structural dynamics of silicon anodes during lithiation and delithiation cycles. A novel cell design for a 18,650 cylindrical cell featuring micro-sized internal speckles within the silicon anode is presented. This design improves the simulation of electrochemical conditions and allows for precise displacement tracking, mitigating impacts on capacity and cycle performance while enhancing Digital Volume Correlation (DVC) analysis. The research prioritizes reducing scan time and radiation exposure in micro-CT assessments of Li-ion cells, and improves the accuracy of internal strain mapping via DVC. Displacement fields over three charging and discharging cycles are documented. Notably, uneven volumetric changes are observed, with local displacements reaching up to 35 µm in areas smaller than 2.5 mm in radius, which contracted during charging and expanded during discharging. This protocol offers insights into the relationship between electrode mechanics and cell performance, promoting non-destructive evaluations of internal structures in commercial cells.

Unraveling Interdiffusion Phenomena and the Role of Nanoscale Diffusion Barriers in the Copper-Gold System.

Diffusion is one of the most fundamental concepts in materials science, playing a pivotal role in materials synthesis, forming, and degradation. Of particular importance is solid state interdiffusion of metals which defines the usable parameter space for material combinations in the form of alloys. This parameter space can be explored on the macroscopic scale by using diffusion couples. However, this method reaches its limit when going to low temperatures, small scales, and when testing ultrathin diffusion barriers. Therefore, this work transfers the principle of the diffusion couples to small scales by using core-shell nanowires and in situ heating. This allows us to delve into the interdiffusion dynamics of copper and gold, revealing the interplay between diffusion and the disorder-order phase transition. Our in situ TEM experiments in combination with chemical mapping reveal the interdiffusion coefficients of Cu and Au at low temperatures and highlight the impact of ordering processes on the diffusion behavior. The formation of ordered domains within the solid-solution is examined using high-resolution imaging and nanodiffraction including strain mapping. In addition, we examine the effectiveness of ultrathin Al2O3 barrier layers to control interdiffusion of the diffusion couple. Our findings indicate that a 5 nm thick layer serves as an efficient diffusion barrier. This research provides valuable insights into the interdiffusion behavior of Cu and Au on the nanoscale, offering potential applications in the development of miniaturized integrated circuits and nanodevices.

Evaluation of U-Notch and V-Notch Geometries on the Mechanical Behavior of PVDF: The DIC Technique and FEA Approach.

The notch effect of semicrystalline PVDF was investigated using U- and V-notch geometries with different depths, and tensile tests were performed at 23 °C using the DIC technique and FEA. Both unnotched and notched dumbbell-shaped specimens were subjected to tensile loading with the DIC technique to obtain mechanical curves and strain maps. The experimental data were compared to a numerical model, analyzing both global mechanical curves and local strain maps around the notch region to assess the accuracy of the simulations. The results demonstrated that the geometry and depth of the notch influence the mechanical behavior of PVDF, presenting a decrease in load and displacement compared to unnotched specimens. This aspect was corroborated by strain maps, which showed the increase in the local strain around the notch tip. For FEA, the global analysis indicated a good correlation with experimental results, and the local analysis demonstrated a reasonable agreement in strain map results within 0.5 mm of the notch neighborhood. Overall, the DIC technique and FEA provided a reliable evaluation of notch behavior on the PVDF used as pressure sheaths with reasonable precision.

A Review: Non-Contact and Full-Field Strain Mapping Methods for Experimental Mechanics and Structural Health Monitoring.

Non-contact and full-field strain mapping captures strain across an entire surface, providing a complete two-dimensional (2D) strain distribution without attachment to sensors. It is an essential technique with wide-ranging applications across various industries, significantly contributing to experimental mechanics and structural health monitoring. Although there have been reviews that focus on specific methods, such as interferometric techniques or carbon nanotube-based strain sensors, a comprehensive comparison that evaluates these diverse methods together is lacking. This paper addresses this gap by focusing on strain mapping techniques specifically used in experimental mechanics and structural health monitoring. The fundamental principles of each method are illustrated with specific applications. Their performance characteristics are compared and analyzed to highlight strengths and limitations. The review concludes by discussing future challenges in strain mapping, providing insights into potential advancements and developments in this critical field.

HyperCAN: Hypernetwork-driven deep parameterized constitutive models for metamaterials

We introduce HyperCAN, a machine learning framework that utilizes hypernetworks to construct adaptable constitutive artificial neural networks for a wide range of beam-based metamaterials exhibiting diverse mechanical behavior under finite deformations. HyperCAN integrates an input convex neural network that models the nonlinear stress–strain map of a truss lattice, while ensuring adherence to fundamental mechanics principles, along with a hypernetwork that dynamically adjusts the parameters of the convex network as a function of the lattice topology and geometry. This unified framework demonstrates robust generalization in predicting the mechanical behavior of previously unseen metamaterial designs and loading scenarios well beyond the training domain. We show how HyperCAN can be integrated into multiscale simulations to accurately capture the highly nonlinear responses of large-scale truss metamaterials, closely matching fully resolved simulations while significantly reducing computational costs. This offers new efficient opportunities for the multiscale design and optimization of truss metamaterials.

Impact of Surface Finishing on Ti6Al4V Voronoi Additively Manufactured Structures: Morphology, Dimensional Deviation, and Mechanical Behavior

Additively manufactured medical devices require proper surface finishing before their use to remove partially adhered particles and provide adequate surface roughness. The literature widely investigates regular lattice structures—mainly scaffolds with small pores to enhance osseointegration; however, only a few studies have addressed the impact of surface finishing on the dimensional deviation and the global and local mechanical responses of lattice samples. Therefore, the current research investigates the impact of biomedical surface finishing (i.e., corundum sandblasting and zirconia sandblasting) on Voronoi lattice structures produced by laser powder bed fusion (LPBF) with large pores and different thicknesses on the surface morphology and global and local mechanical behaviors. MicroCT and SEM are performed for the assessment of dimensional mismatch and surface evaluation. The mechanical properties are investigated with 2D digital image correlation (DIC) in quasi-static compression tests to estimate the impact of surface finishes on local maps of strain. In the quasi-static tests, both the global mechanical performances, as expected, and local 2D DIC strain maps were mainly affected by the strut thickness, and the impact of different surface finishings was irrelevant; on the contrary, different surface finishing processes led to differences in the dimensional deviation depending on the strut thickness. These results are relevant for designing lattice structures with thin struts that are integrated into medical prostheses that undergo AM.

Cardiovascular Magnetic Resonance Imaging of Takotsubo Syndrome: Evolving Diagnostic and Prognostic Perspectives.

Takotsubo syndrome (TS) is a temporary form of left ventricular (LV) dysfunction characterized by a distinct pattern of LV impairment, often triggered by a physical or emotional stressful event. Historically, TS was considered a benign condition due to its prompt restoration of myocardial function and generally excellent outcomes. However, recent studies have shown that complications similar to those seen after myocardial infarction can occur, necessitating careful monitoring of these patients. Among noninvasive imaging techniques, cardiovascular magnetic resonance (CMR) is becoming increasingly important in evaluating patients with TS. CMR offers a unique ability to noninvasively assess myocardial tissue characteristics, allowing for detecting the typical features of TS, such as specific wall motion abnormalities and myocardial edema. Beyond its well-established diagnostic utility in the clinical management of TS, CMR has also proven valuable in prognosis and risk stratification for these patients. Advances in CMR, including myocardial strain and parametric mapping have expanded its role in the diagnosis, prognosis, and follow-up of these patients. This review aims to provide a comprehensive overview of the potential applications of CMR in the diagnostic and prognostic evaluation of TS patients. It explores the emerging use of novel CMR imaging biomarkers that may enhance diagnosis, improve prognostic accuracy, and contribute to the overall management of these patients.