Dark-field Imaging Research Articles

Multimodal measurement of glycocalyx degradation during coronary artery bypass grafting.

Glycocalyx shedding and subsequent endothelial dysfunction occur in many conditions, such as in sepsis, in critical illness, and during major surgery such as in coronary artery bypass grafting (CABG) where it has been shown to associate with organ dysfunction. Hitherto, there is no consensus about the golden standard in measuring glycocalyx properties in humans. The objective of this study was to compare different indices of glycocalyx shedding and dysfunction. To this end, we studied patients undergoing elective CABG surgery, which is a known cause of glycocalyx shedding. Sublingual glycocalyx thickness was measured in 23 patients by: 1) determining the perfused boundary region (PBR)-an inverse measure of glycocalyx thickness-by means of sidestream dark field imaging technique. This is stated double, 2) measuring plasma levels of the glycocalyx shedding products syndecan-1, hyaluronan, and heparan sulfate and 3) measuring plasma markers of impaired glycocalyx function and endothelial activation (Ang-2, Tie-2, E-selectin, and thrombomodulin). Measurements were performed directly after induction, directly after onset of cardiopulmonary bypass (CPB), and directly after cessation of CPB. We assessed changes over time as well as correlations between the various markers. The PBR increased from 1.81 ± 0.21 μm after induction of anesthesia to 2.27 ± 0.25 μm (p < 0.0001) directly after CPB was initiated and did not change further during CPB. A similar pattern was seen for syndecan-1, hyaluronan, heparan sulfate, Ang-2, Tie-2, and thrombomodulin. E-selectin levels also increased between induction and the start of CPB and increased further during CPB. The PBR correlated moderately with heparan sulfate, E-selectin, and thrombomodulin and weakly with Syndecan-1, hyaluronan, and Tie-2. Shedding markers syndecan-1 and hyaluronan correlated with all functional markers. Shedding marker heparan sulfate only correlated with Tie-2, thrombomodulin, and E-selectin. Thrombomodulin correlated with all shedding markers. Our results show that glycocalyx thinning, illustrated by increased sublingual PBR and increased levels of shedding markers, is paralleled with impaired glycocalyx function and increased endothelial activation in CABG surgery with CPB. As correlations between different markers were limited, no single marker could be identified to represent the glycocalyx in its full complexity.

Improving data quality for three-dimensional electron diffraction by a post-column energy filter and a new crystal tracking method.

Three-dimensional electron diffraction (3D ED) has become an effective technique to determine the structures of submicrometre- (nanometre-)sized crystals. In this work, energy-filtered 3D ED was implemented using a post-column energy filter in both STEM mode and TEM mode [(S)TEM denoting (scanning) transmission electron microscope]. The setups for performing energy-filtered 3D ED on a Gatan imaging filter are described. The technique and protocol improve the accessibility of energy-filtered 3D ED post-column energy filters, which are available in many TEM laboratories. In addition, a crystal tracking method in STEM mode using high-angle annular dark-field imaging is proposed. This method enables the user to monitor the crystal position while collecting 3D ED data at the same time, allowing a larger tilt range without foregoing any diffraction frames or imposing extra electron dose. In order to compare the differences between energy-filtered and unfiltered 3D ED data sets, three well known crystallized inorganic samples have been studied in detail. For these samples, the final R 1 values improved by 10-30% for the energy-filtered data sets compared with the unfiltered data sets, and the structures became more chemically reasonable. Possible reasons for improvement are also discussed.

Different atomic contrasts in HAADF images and EELS maps of rutile TiO2.

High-angle annular dark-field (HAADF) imaging and elemental mapping at the atomic scale by scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) are widely used for material characterization, in which quantitative understanding of the contrast of the image is required. Here, we report an unexpected image contrast in the elemental mapping of rutile TiO2, where the Ti L2,3 map shows an anisotropic elliptical shape that extends along the long axis in the octahedral structure, while the atomic contrast of Ti columns in the HAADF image is almost circular. Multi-slice simulation reveals that unique electron channeling related to the rutile structure and the difference of the potentials between HAADF and EELS cause the different atomic contrasts in the two images.

Dark-field chest X-ray imaging for the assessment of COVID-19-pneumonia

BackgroundCurrently, alternative medical imaging methods for the assessment of pulmonary involvement in patients infected with COVID-19 are sought that combine a higher sensitivity than conventional (attenuation-based) chest radiography with a lower radiation dose than CT imaging.MethodsSixty patients with COVID-19-associated lung changes in a CT scan and 40 subjects without pathologic lung changes visible in the CT scan were included (in total, 100, 59 male, mean age 58 ± 14 years). All patients gave written informed consent. We employed a clinical setup for grating-based dark-field chest radiography, obtaining both a dark-field and a conventional attenuation image in one image acquisition. Attenuation images alone, dark-field images alone, and both displayed simultaneously were assessed for the presence of COVID-19-associated lung changes on a scale from 1 to 6 (1 = surely not, 6 = surely) by four blinded radiologists. Statistical analysis was performed by evaluation of the area under the receiver–operator-characteristics curves (AUC) using Obuchowski’s method with a 0.05 level of significance.ResultsWe show that dark-field imaging has a higher sensitivity for COVID-19-pneumonia than attenuation-based imaging and that the combination of both is superior to one imaging modality alone. Furthermore, a quantitative image analysis shows a significant reduction of dark-field signals for COVID-19-patients.ConclusionsDark-field imaging complements and improves conventional radiography for the visualisation and detection of COVID-19-pneumonia.

Variability of microcirculatory measurements in healthy volunteers

Reliable assessment of the microcirculation is important to investigate microcirculatory properties in various disease states. The GlycoCheck system automatically analyzes sublingual sidestream dark field images to determine the perfused boundary region (PBR; a measure of glycocalyx thickness), red blood cell filling percentage, and microvascular vessel density. Although GlycoCheck has been used to study the microcirculation in patients, little is known about the reproducibility of measurements in healthy volunteers. We assessed intra- and interobserver agreement by having two experienced observers perform three consecutive microcirculation measurements with the GlycoCheck system in 49 healthy volunteers. Intraobserver agreement of single measurements were poor (intraclass correlation coefficients (ICCs) < 0.4) for PBR, red blood cell filling percentage and microvascular vessel density. ICCs increased to values > 0.6 (indicating good reproducibility) for all parameters when performing and averaging three consecutive measurements. No systematic differences were observed between observers for any parameter. Interobserver variability was fair for PBR (ICC = 0.53) and red blood cell filling percentage (ICC = 0.58) and poor for perfused vessel density (ICC = 0.20). In conclusion, GlycoCheck software can be used with acceptable reliability and reproducibility for microcirculation measurements on a population level when averaging three consecutive measurements. Repeated measurements are preferably performed by the same observer.

Large refrigerant capacity in superparamagnetic iron nanoparticles embedded in a thin film matrix

A magnetocaloric effect (MCE) with sizable isothermal entropy change (ΔS) maintained over a broad range of temperatures above the blocking temperature is reported for a rare earth-free superparamagnetic nanoparticle system comprising of Fe–TiN heterostructure. Superparamagnetic iron (Fe) particles were embedded in a titanium nitride (TiN) thin film matrix in a TiN/Fe/TiN multilayered pattern using a pulsed laser deposition method. High angle annular dark-field images in conjunction with dispersive energy analysis, recorded using scanning transmission electron microscopy, show a clear presence of alternating layers of Fe and TiN with a distinct atomic number contrast between Fe particles and TiN. Quantitative information about the isothermal entropy change (ΔS) and the magnetocaloric effect in the multilayer Fe–TiN system has been obtained by applying Maxwell relation to the magnetization vs temperature data at various fields. With the absence of a dynamic magnetic hysteresis above the blocking temperature, the negative ΔS as high as 4.18 × 103 J/Km3 (normal or forward MCE) is obtained at 3 T at 300 K.

Improving Data Quality in Traditional Low‐Dose Scanning Transmission Electron Microscopy Imaging

AbstractIt has become very important to study and find optimal conditions for imaging electron‐beam (e‐beam) sensitive materials in scanning transmission electron microscopy under low electron‐dose with high signal‐to‐noise ratio (SNR). Convergence and collection angles and electron‐probe current are essential parameters. However, these parameters have rarely been discussed in a systematic way. In this paper, the illumination and collection conditions are optimized according to the resolution requirement of different materials by adjusting the condenser and intermediate lenses in a commercial transmission electron microscope. To demonstrate the significance of optimizing these parameters, two examples, zeolite MFI and metal–organic framework (MOF) MIL‐101, are taken among the sensitive materials, with the most important electron incidences along the [010] and &lt;110&gt; directions, respectively. High SNR atomic resolution images of MFI are obtained with e‐beam current as low as 0.50 pA, reaching information transfer for reflection up to 18 0 2 corresponding to d‐spacing of 0.11 nm, close to the resolution limit of 0.098 nm from resolvable diffraction limit. MOF MIL‐101 is characterized under an even lower e‐beam 0.2 pA to avoid severe beam damage. High‐quality annular dark and bright field images are obtained, which proves the wide applicability of this method on more e‐beam sensitive materials.

Effects of flexoelectric polarization on surface potential of dielectric thin-film heterostructures: A comparative study

Recently, flexoelectric effect has attracted considerable attention owing to ubiquitous existence in all dielectrics, regardless of the symmetry. It promises intriguingly physical phenomena, such as strain gradient-induced electric polarizations, photocurrents, and interfacial transports, as well as their electromechanical coupling with external force loading, in diverse materials for multifunctional applications in electronics. In this work, we report the flexoelectric-modulation on surface potential of LaFeO3 (LFO) thin-film heterostructures. The LFO thin film with or without the flexoelectric effect has been achieved by controlling epitaxial misfit against a substrate. Lattice structures and strain behaviors are observed by atomic-resolution high-angle annular dark-field imaging. Grown on a LaAlO3 substrate, a giant strain gradient of ∼3 × 106 m−1 is generated in the LFO thin film due to the gradual relaxation of large misfit strain with increasing thickness, yielding a robust flexoelectric polarization pointing to the heterostructure surface. In contrast, the LFO is almost fully strained on a SrTiO3 substrate due to the small lattice mismatch. The flexoelectric polarization results in an increase in surface potential in the LFO heterostructure due to the incomplete screening of positive polarization bound charges, as observed by scanning kelvin probe microscopy. Furthermore, x-ray photoelectron spectroscopy reveals that the flexoelectric polarization can downward bend the band alignment of the LFO layer and modulate the interfacial potential barriers. These results provide the way for experimental observations of the flexoelectric effect and deliver physical insight into deep understanding of interfacial electronic structures of flexoelectric-based devices.

Identifying a sublingual triangle as the ideal site for assessment of sublingual microcirculation

The sublingual mucosa is a commonly used intraoral location for identifying microcirculatory alterations using handheld vital microscopes (HVMs). The anatomic description of the sublingual cave and its related training have not been adequately introduced. The aim of this study was to introduce anatomy guided sublingual microcirculatory assessment. Measurements were acquired from the floor of the mouth using incident dark-field (IDF) imaging before (T0) and after (T1) sublingual cave anatomy instructed training. Instructions consists of examining a specific region of interested identified through observable anatomical structures adjacent and bilaterally to the lingual frenulum which is next to the sublingual papilla. The anatomical location called the sublingual triangle, was identified as stationed between the lingual frenulum, the sublingual fold and ventrally to the tongue. Small, large, and total vessel density datasets (SVD, LVD and TVD respectively) obtained by non-instructed and instructed measurements (NIN (T0) and IM (T1) respectively) were compared. Microvascular structures were analyzed, and the presence of salivary duct-related microcirculation was identified. A total of 72 video clips were used for analysis in which TVD, but not LVD and SVD, was higher in IM compared to NIM (NIM vs. IM, 25 ± 2 vs. 27 ± 3 mm/mm2 (p = 0.044), LVD NIM vs. IM: 7 ± 1 vs. 8 ± 1mm/mm2 (p = 0.092), SVD NIM vs. IM: 18 ± 2 vs. 20 ± 3 mm/mm2 (p = 0.103)). IM resulted in microcirculatory assessments which included morphological properties such as capillaries, venules and arterioles, without salivary duct-associated microcirculation. The sublingual triangle identified in this study showed consistent network-based microcirculation, without interference from microcirculation associated with specialized anatomic structures. These findings suggest that the sublingual triangle, an anatomy guided location, yielded sublingual based measurements that conforms with international guidelines. IM showed higher TVD values, and future studies are needed with larger sample sizes to prove differences in microcirculatory parameters.

Contrastive learning-based image retrieval for automatic recognition of in situ marine plankton images

Abstract Automatic recognition of in situ marine plankton images has long been treated as an image classification problem in machine learning. However, the deep learning-based classifiers are far from robust when used for predicting actual oceanic data that inevitably has distributional and compositional variations from their training sets. This paper proposes a novel image retrieval-based framework for plankton image recognition, within which supervised contrastive learning is used to train a feature extractor for better image representation, and similarity between the input and a gallery of reference images is compared to determine the identity of queries. We construct a dataset of high-quality in situ dark-field images of plankton and suspended particles to train and test the proposed retrieval model. Experimental results show that the image retrieval method has achieved excellent recognition performance similar to the state-of-the-art classification models on a very imbalanced closed-set, and also exhibited better generalizability in dealing with dataset shift and out-of-distribution issues. In addition, the image retrieval method has also demonstrated great architectural flexibility, bringing practical convenience for its adaptation to complex marine application scenarios. This new recognition framework is expected to enable real-time in situ observation of marine plankton in the actual oceanic underwater environment in the near future.

Selective area heteroepitaxy of InAs nanostructures on nanopillar-patterned GaAs(111)A

A process sequence enabling the large-area fabrication of nanopillar-patterned semiconductor templates for selective-area heteroepitaxy is developed. Herein, the nanopillar tops surrounded by a SiNx mask film serve as nanoscale growth areas. The molecular beam epitaxial growth of InAs on such patterned GaAs(111)A templates is investigated by means of electron microscopy. It is found that defect-free nanoscale InAs islands grow selectively on the nanopillar tops at a substrate temperature of 425 °C. High-angle annular dark-field scanning transmission electron microscopy imaging reveals that for a growth temperature of 400 °C, the InAs islands show a tendency to form wurtzite phase arms extending along the lateral ⟨112¯⟩ directions from the central zinc blende region of the islands. This is ascribed to a temporary self-catalyzed vapor–liquid–solid growth on {111¯} B facets, which leads to a kinetically induced preference for the nucleation of the wurtzite phase driven by the local, instantaneous V/III ratio, and to a concomitant reduction of surface energy of the nanoscale diameter arms.

Imaging Breast Microcalcifications Using Dark-Field Signal in Propagation-Based Phase-Contrast Tomography

Breast microcalcifications are an important primary radiological indicator of breast cancer. However, microcalcification classification and diagnosis may be still challenging for radiologists due to limitations of the standard 2D mammography technique, including spatial and contrast resolution. In this study, we propose an approach to improve the detection of microcalcifications in propagation-based phase-contrast X-ray computed tomography of breast tissues. Five fresh mastectomies containing microcalcifications were scanned at different X-ray energies and radiation doses using synchrotron radiation. Both bright-field (i.e. conventional phase-retrieved images) and dark-field images were extracted from the same data sets using different image processing methods. A quantitative analysis was performed in terms of visibility and contrast-to-noise ratio of microcalcifications. The results show that while the signal-to-noise and the contrast-to-noise ratios are lower, the visibility of the microcalcifications is more than two times higher in the dark-field images compared to the bright-field images. Dark-field images have also provided more accurate information about the size and shape of the microcalcifications.

Microvascular perfusion, perfused boundary region and glycocalyx shedding in patients with autosomal dominant polycystic kidney disease: results from the GlycoScore III study.

Vascular abnormalities and endothelial dysfunction are part of the spectrum of autosomal dominant polycystic kidney disease (ADPKD). The mechanisms behind these manifestations, including potential effects on the endothelial surface layer (ESL) and glycocalyx integrity, remain unknown. Forty-five ambulatory adult patients with ADPKD were enrolled in this prospective, observational, cross-sectional, single-centre study. Fifty-one healthy volunteers served as a control group. All participants underwent real-time microvascular perfusion measurements of the sublingual microcirculation using sidestream dark field imaging. After image acquisition, the perfused boundary region (PBR), an inverse parameter for red blood cell (RBC) penetration into the ESL, was automatically calculated. Microvascular perfusion was assessed by RBC filling and capillary density. Concentrations of circulating glycocalyx components were determined by enzyme-linked immunosorbent assay. ADPKD patients showed a significantly larger PBR compared with healthy controls (2.09±0.23µm versus 1.79±0.25µm; P<.001). This was accompanied by significantly lower RBC filling (70.4±5.0% versus 77.9±5.4%; P<.001) as well as a higher valid capillary density {318/mm2 [interquartile range (IQR) 269-380] versus 273/mm2 [230-327]; P=.007}. Significantly higher plasma concentrations of heparan sulphate (1625±807ng/ml versus 1329±316ng/ml; P=.034), hyaluronan (111ng/ml [IQR 79-132] versus 92ng/ml [82-98]; P=.042) and syndecan-1 were noted in ADPKD patients compared with healthy controls (35ng/ml [IQR 27-57] versus 29ng/ml [23-42]; P=.035). Dimensions and integrity of the ESL are impaired in ADPKD patients. Increased capillary density may be a compensatory mechanism for vascular dysfunction to ensure sufficient tissue perfusion and oxygenation.

Bulk morphology of porous materials at submicrometer scale studied by dark-field x-ray imaging with Hartmann masks

We present the quantitative investigation of the submicron structure in the bulk of porous graphite by using the dark-field x-ray imaging with Hartmann masks. By scanning the correlation length and measuring the mask visibility reduction, we obtain the average pore size, relative pore fraction, fractal dimension, and Hurst exponent of the structure in a simple and flexible setup with relaxed requirements on beam coherence. Profiting from the dimensionality of the mask, we obtain scattering signals in two orthogonal directions, which reveals the anisotropy of pore sizes.

High signal-to-noise ratio and high contrast dark-field confocal imaging of subsurface defects

The weak scattering characteristic of subsurface defects (SSD) and the scattering noise from substrate can result in a low SNR and low contrast DFCM image. By applying the proposed high signal-to-noise ratio imaging and details preserving noise reduction algorithm based on TSVD and PCA and an image-adjustment-function, the high signal-to-ratio (SNR) and high contrast dark-field confocal microscopy (DFCM) imaging of SSD is realized. The SNR of the DFCM image is demonstrated a meaningful enhancement of 8.71 times. The proposed method is demonstrated on microscopic images with micron sized SSD structures. At last, we use the processed images for 3D reconstruction. The reconstructed results have higher SNR and contrast and can display more details of SSD.

Mapping structural heterogeneity at the nanoscale with scanning nano-structure electron microscopy (SNEM)

Here we explore the use of scanning electron diffraction (also known as 4D-STEM) coupled with electron atomic pair distribution function analysis (ePDF) to understand the local order (structure and chemistry) as a function of position in a complex multicomponent system, a hot rolled, Ni-encapsulated, Zr65Cu17.5Ni10Al7.5 bulk metallic glass (BMG), with a spatial resolution of 3 nm. We show that it is possible to gain insight into the chemistry and chemical clustering/ordering tendency in different regions of the sample, including in the vicinity of nano-scale crystallites that are identified from virtual dark field images and in heavily deformed regions at the edge of the BMG. In addition to simpler analysis, unsupervised machine learning was used to extract partial PDFs from the material, modeled as a quasi-binary alloy, and map them in space. These maps allowed key insights not only into the local average composition, as validated by EELS, but also a unique insight into chemical short-range ordering tendencies in different regions of the sample during formation. The experiments are straightforward and rapid and, unlike spectroscopic measurements, don’t require energy filters on the instrument. We spatially map different quantities of interest (QoI’s), defined as scalars that can be computed directly from positions and widths of ePDF peaks or parameters refined from fits to the patterns. We developed a flexible and rapid data reduction and analysis software framework that allows experimenters to rapidly explore images of the sample on the basis of different QoI’s. The power and flexibility of this approach are explored and described in detail. Because of the fact that we are getting spatially resolved images of the nanoscale structure obtained from ePDFs we call this approach scanning nano-structure electron microscopy (SNEM), and we believe that it will be powerful and useful extension of current 4D-STEM methods.

Exploration of the X-ray Dark-Field Signal in Mineral Building Materials.

Mineral building materials suffer from weathering processes such as salt efflorescence, freeze–thaw cycling, and microbial colonization. All of these processes are linked to water (liquid and vapor) in the pore space. The degree of damage following these processes is heavily influenced by pore space properties such as porosity, pore size distribution, and pore connectivity. X-ray computed micro-tomography (µCT) has proven to be a valuable tool to non-destructively investigate the pore space of stone samples in 3D. However, a trade-off between the resolution and field-of-view often impedes reliable conclusions on the material’s properties. X-ray dark-field imaging (DFI) is based on the scattering of X-rays by sub-voxel-sized features, and as such, provides information on the sample complementary to that obtained using conventional µCT. In this manuscript, we apply X-ray dark-field tomography for the first time on four mineral building materials (quartzite, fired clay brick, fired clay roof tile, and carbonated mineral building material), and investigate which information the dark-field signal entails on the sub-resolution space of the sample. Dark-field tomography at multiple length scale sensitivities was performed at the TOMCAT beamline of the Swiss Light Source (Villigen, Switzerland) using a Talbot grating interferometer. The complementary information of the dark-field modality is most clear in the fired clay brick and roof tile; quartz grains that are almost indistinguishable in the conventional µCT scan are clearly visible in the dark-field owing to their low dark-field signal (homogenous sub-voxel structure), whereas the microporous bulk mass has a high dark-field signal. Large (resolved) pores on the other hand, which are clearly visible in the absorption dataset, are almost invisible in the dark-field modality because they are overprinted with dark-field signal originating from the bulk mass. The experiments also showed how the dark-field signal from a feature depends on the length scale sensitivity, which is set by moving the sample with respect to the grating interferometer.

Extension of focal depth by electron quasi-Bessel beam in atomic-resolution scanning transmission electron microscopy

Extension of the focal depth of a sub-nanometer-sized electron probe in a scanning transmission electron microscope was demonstrated using an electron Bessel beam. We observed atomically-resolved annular dark-field scanning transmission electron microscope images of SrTiO3 in the [001] direction with defocus using an electron quasi-Bessel beam generated by a ring-shaped aperture in an aberration-corrected probe-forming system. The experimental results show that the defocus range over which images with a 0.2 nm spatial resolution can be acquired using the electron quasi-Bessel beam is three times longer than the corresponding defocus range for a conventional beam.

Simulating dark-field X-ray microscopy images with wavefront propagation techniques

Dark-field X-ray microscopy is a diffraction-based synchrotron imaging technique capable of imaging defects in the bulk of extended crystalline samples. Numerical simulations are presented of image formation in such a microscope using numerical integration of the dynamical Takagi-Taupin equations and wavefront propagation. The approach is validated by comparing simulated images with experimental data from a near-perfect single crystal of diamond containing a single stacking-fault defect in the illuminated volume.

Microscopic Insights into the Inhomogeneous Degradation of Pt Alloy Catalysts in PEM Fuel Cells

Fuel cell electric vehicles (FCEVs) powered by proton exchange membrane fuel cells (PEMFCs) offer a sustainable, low-carbon alternative to the world’s current energy structure based on fossil fuels. Recently, application of PEMFC to heavy-duty vehicles (HDVs) has attracted significant interest for reducing greenhouse gas emissions in this market. Relative to passenger vehicles, HDVs require extended lifetimes and high operating costs, leading to an increased emphasis on the durability and efficiency of membrane electrode assembly components [1].Degradation of the oxygen reduction reaction (ORR) cathode catalyst is one of the main challenges for heavy duty applications. Several degradation mechanisms have been identified, such as Ostwald ripening, particle coalescence/migration, and particle detachment, the observation of which relies on transmission electron microscopy (TEM) [2,3]. Through TEM, inhomogeneous degradation at the micro- and nanoscale during operation have been observed: (1) the Pt loading decreases toward the cathode/membrane interface and creates a depletion zone adjacent to the interface [2,4] and (2) different rates of electrochemical surface area loss of PtCo supported on various porous carbons,[5] leading to the speculation of different degradation rates for particles at the exterior vs. interior carbon surfaces.To elucidate these inhomogeneous degradation mechanisms, we employ high-throughput image analysis and electron tomography methods to analyze fuel cell cathodes before and after accelerated stress tests (ASTs) performed in both nitrogen and air environments. An automated, high-throughput method was developed that provides statistically relevant analysis of PtCo particle size, shape, and loading distribution. This method combines automated image or energy-dispersive spectroscopy (EDS) map acquisition using a commercial software (MAPS, Thermo Fisher Scientific) and custom Python codes to analyze high-angle annular dark field (HAADF) and EDS spectrum images. With the high-throughput method, we reveal the inhomogeneous distribution of PtCo particle size, Pt loading, and Co content across the entire electrode. In addition, an electron tomography workflow is under development to measure PtCo particle size and composition on the exterior and interior of the porous carbon support. The effect of cathode gaseous environment on the distribution of particle size, loading, and composition is discussed at the microscale across the electrode and at the nanoscale for exterior and interior surfaces of primary carbon particles. Findings from this study will provide new mitigation strategies and design principles to enable durable fuel cell catalysts.[6]References[1] DA Cullen et al., Nat. Energy. 6 (2021), p. 462.[2] PJ Ferreira et al., J. Electrochem. Soc. 152 (2005), p. A2256.[3] R Borup et al., Chem. Rev. 107 (2007), p. 3904.[4] H Yu et al., Electrochim. Acta 247 (2017), p. 1169.[5] M Ko et al., J. Electrochem. Soc. 168 (2021), p. 24512.[6] This material is based on work performed by the Million Mile Fuel Cell Truck (M2FCT) Consortium, technology managers Greg Kleen and Dimitrios Papageorgopoulus, which is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, and by U.S. Department of Energy, Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities. Electron microscopy research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).