Phase Contrast X-ray Microscopy Research Articles

Operando ultra-high-resolution X-ray microscopy of lithium anodes with separator interactions

Lithium (Li) metal is an attractive anode material candidate for high-energy-density battery systems that could enable challenging electrification applications, such as flight and heavy-duty vehicles. However, the formation of porous deposits and dendrites during cycling cause capacity loss and internal short-circuit risks. Here, we use high-resolution in-situ/operando Zernike phase contrast X-ray microscopy to directly visualize the lithium electrodeposition process inside a coin cell with a commercial separator. The nucleation and subsequent lithium electrodeposition were imaged by transmission X-ray microscopy (TXM) at 150 nm spatial resolution and <2 min temporal resolution. The resulting lithium deposits were then reconstructed into three-dimensional (3D) volumes by computed tomography (CT), revealing the Li structures above, at, and below the anode/separator interface. Distinct nucleation and deposition mechanisms were observed under varied cell temperatures, charging current density, and electrolyte composition. This work demonstrates the unique strengths of combining TXM and CT imaging techniques: the dynamic evolution of lithium electrodeposition and the comprehensive morphology of the resulting structure were characterized together. Furthermore, our results indicate the importance of in-situ/operando characterization of systems in commercially-relevant configurations in developing practical dendrite mitigation strategies.

Freestanding high-aspect-ratio gold masks for low-energy, phase-based x-ray microscopy

High-resolution, x-ray phase contrast microscopy, a key technique with promising potential in biomedical imaging and diagnostics, is based on narrow-slit high-aspect-ratio gold gratings. We present the development, fabrication details, and experimental testing of the freestanding 10 μm thick gold membrane masks with an array of 0.9–1.5 μm void slit apertures for a novel low-energy x-ray microscope. The overall mask size is 4 mm × 4 mm, with a grating pitch of 7.5 μm, 6.0–6.6 μm wide gold bars are supported by 3 μm wide crosslinks at 400 μm intervals. The fabrication process is based on gold electroplating into a silicon mold coated with various thin films to form a voltage barrier, plating base, and sacrificial layer, followed by the mold removal to obtain the freestanding gold membrane with void slit apertures. We discuss key aspects for the materials and processes, including gold structures homogeneity, residual stresses, and prevention of collapsing of the grid elements. We further demonstrate the possibility to obtain high-resolution, high contrast 2D images of biological samples using an incoherent, rotating anode x-ray tube.

Phase-contrast X-ray Imaging and Microscopy for Crystallographic Applications at EMBL Beamline P14 of PETRA III

Phase-contrast X-ray Imaging and Microscopy for Crystallographic Applications at EMBL Beamline P14 of PETRA III

Phase-contrast hard X-ray microscopy using synchrotron radiation for the properties of skeletal muscle in mouse hind limbs.

Radiation beam interface contrast X-ray microscopy provides resolution of a few dozen nanometers from fixed whole muscle biopsies, allowing better reconstruction of the microstructure of the muscle than is currently possible with classic histological techniques. Fixed soleus muscle biopsies have been evaluated from the walk-in mouse model using phase-contrast X-ray microscopy, and results presented that corroborate the accuracy of the method used, and its potential for application in physiotherapy and occupational therapy studies. We believe that this method will enhance existing morphometric methods of analysis, leading to accurate reconstruction of other thick specimens that would otherwise require thin sectioning and reconstruction through deconvolution algorithms.

Development toward high-resolution X-ray phase imaging.

Since the 1990s, the use of X-ray phase contrast has been extensively studied for imaging weakly absorbing objects consisting of low-Z elements such as biological soft tissues and polymers. The development of X-ray microscopy was also progressing during this time, although absorption contrast was only available. It was straightforward and important to develop phase-contrast X-ray microscopy. One characteristic in the development is that quantitative phase measurement is possible through the acquisition of phase-contrast images under a specific procedure, thanks to digital X-ray image detectors. Therefore, such a technique is called 'phase imaging' rather than phase-contrast imaging in this review. Highly sensitive three-dimensional phase imaging is feasible in combination with tomography. This article reviews the progress in X-ray phase imaging, especially with regards to X-ray microscopy.

Characterising the structural properties of polymer separators for lithium-ion batteries in 3D using phase contrast X-ray microscopy

Separators are an integral component for optimising performance and safety of lithium-ion batteries; therefore, a clear understanding of how their microstructure affects cell performance and safety is crucial. Phase contrast X-ray microscopy is used here to capture the microstructures of commercial monolayer, tri-layer, and ceramic-coated lithium-ion battery polymer separators. Spatial variations in key structural parameters, including porosity, tortuosity factor and pore size distribution, are determined through the application of 3D quantification techniques and stereology. The architectures of individual layers in multi-layer membranes are characterised, revealing anisotropy in porosity, tortuosity factor and mean pore size of the three types of separator. Detailed structural properties of the individual layers of multi-layered membranes are then related with their expected effect on safety and rate capability of cells.

X-Ray Nanoscopy of a Bulk Heterojunction.

Optimizing the morphology of bulk heterojunctions is known to significantly improve the photovoltaic performance of organic solar cells, but available quantitative imaging techniques are few and have severe limitations. We demonstrate X-ray ptychographic coherent diffractive imaging applied to all-organic blends. Specifically, the phase-separated morphology in bulk heterojunction photoactive layers for organic solar cells, prepared from a 50:50 blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) and thermally treated for different annealing times is imaged to high resolution. Moreover, using a fast-scanning calorimetry chip setup, the nano-morphological changes caused by repeated thermal annealing applied to the same sample could be monitored. X-ray ptychography resolves to better than 100 nm the phase-segregated domains of electron donor and electron acceptor materials over a large field of view within the active layers. The quantitative phase contrast images further allow us to estimate the local volume fraction of PCBM across the photovoltaically active layers. The volume fraction gradient for different regions provides insight on the PCBM diffusion across the depletion zone surrounding PCBM aggregates. Phase contrast X-ray microscopy is under rapid development, and the results presented here are promising for future studies of organic-organic blends, also under in situ conditions, e.g., for monitoring the structural stability during UV-Vis irradiation.

Performance analysis of quantitative phase retrieval method in Zernike phase contrast X-ray microscopy*Supported by the State Key Project for Fundamental Research (2012CB825801), National Natural Science Foundation of China (11475170, 11205157 and 11179004) and Anhui Provincial Natural Science Foundation (1508085MA20).

Since the invention of Zernike phase contrast method in 1930, it has been widely used in optical microscopy and more recently in X-ray microscopy. Considering the image contrast is a mixture of absorption and phase information, we recently have proposed and demonstrated a method for quantitative phase retrieval in Zernike phase contrast X-ray microscopy. In this contribution, we analyze the performance of this method at different photon energies. Intensity images of PMMA samples are simulated at 2.5 keV and 6.2 keV, respectively, and phase retrieval is performed using the proposed method. The results demonstrate that the proposed phase retrieval method is applicable over a wide energy range. For weakly absorbing features, the optimal photon energy is 2.5 keV, from the point of view of image contrast and accuracy of phase retrieval. On the other hand, in the case of strong absorption objects, a higher photon energy is preferred to reduce the error of phase retrieval. These results can be used as guidelines to perform quantitative phase retrieval in Zernike phase contrast X-ray microscopy with the proposed method.

Laboratory x-ray microscopy on high brilliance sources equipped with waveguides

We report on the experimental realization of propagation-based x-ray microscopy with laboratory sources equipped with waveguides. We discuss about the experimental setup, the fabrication steps, and the characterization procedures of the waveguide optics. We demonstrate that the system enables high resolution attenuation imaging of poorly absorbing biological specimens. Furthermore, we report the successful realization of propagation-based phase contrast x-ray microscopy, enabling quantitative thickness estimation in homogeneous objects. Advantages and major limitations of the experimental scheme are presented and discussed.

Laboratory-based multi-modal X-ray microscopy and micro-CT with Bragg magnifiers.

We report on the successful demonstration of X-ray phase contrast microscopy and micro computed tomography (CT) with a Bragg magnifier microscope (BMM) in a laboratory setup. The Bragg magnifiers, constituted by two channel-cut crystals in asymmetric diffraction, produced a 15X magnification of the X-ray beam, thus enabling high resolution imaging to be attained. The angular sensitivity of the crystals was used to implement analyzer-based phase contrast imaging: acquiring images at different angular positions and the three parametric images (apparent absorption, differential phase and scattering) have been obtained. Micro-CT, with resolution of about 5 μm is demonstrated with the same system. The main limitations, as well as the ways to mitigate them, are discussed with the aid of the experimental data. The technique demonstrated herein extends high-resolution, multi-modal, x-ray imaging and micro-CT to compact laboratory setups, with the potential of broadening the reach of these techniques outside the community of synchrotron users.

Mechanisms of the formation of morphological features of micropipes in bulk crystals of silicon carbide

New morphological features of dislocation micropipes in silicon carbide single crystals have been investigated experimentally and theoretically. It has been shown that the cylindrical shape of micropipes is unstable, and the cross-sectional sizes of the micropipes change along their axes. The experimental results have been obtained by measuring X-ray phase-contrast microscopy images of micropipes in highly coherent synchrotron radiation. The cross-sectional sizes of the micropipes have been determined using computer simulation of their images. A theoretical model of the transformation of dislocations into micropipes due to nonequilibrium processes of pipe diffusion and coagulation of vacancies on dislocations parallel to the crystal growth axis has been proposed.

Edge-enhanced Soft X-ray Phase-contrast Microscopy Exploiting the Near K-edge Optical Properties of Carbon

Edge-enhanced Soft X-ray Phase-contrast Microscopy Exploiting the Near K-edge Optical Properties of Carbon

回折格子を利用した高感度X線結像顕微鏡

X-ray microscopy is one of promising candidates to non-destructively visualize internal structures in samples under extreme environments. We have developed a high-sensitive X-ray imaging microscope consisting of an objective lens and a transmission grating. The microscope is based on the Talbot effect of the grating and works simply by appending the grating to an X-ray imaging microscope. Our approach has several advantages over the Zernike X-ray phase-contrast microscopy that has been widely used, and can provide a powerful way of quantitative visualization with a high spatial resolution and a high sensitivity even for relatively thick samples.

Visualization of nanoscale deformation in polymer composites with zernike-type phase-contrast X-ray microscopy and the finite element method

We visualized the strain field of a polymer matrix using a finite element method (FEM) simulation based on knowledge of the three-dimensional (3D) structural configuration of silica particles in rubber. The 3D structural configuration was obtained using the Zernike-type phase contrast X-ray imaging method. Based on the structural information, the inhomogeneous local deformation of the rubber matrix was visualized using the FEM simulation. We visualized strain field of polymer matrix using an FEM simulation based on the knowledge of 3D structural configuration of silica particles in rubber. The configuration was obtained by using the Zernike-type phase contrast x-ray imaging method.

Large volume, non-destructive 3D analysis of low-density materials and interfaces with phase contrast X-ray microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Advantages of intermediate X-ray energies in Zernike phase contrast X-ray microscopy

Understanding the hierarchical organizations of molecules and organelles within the interior of large eukaryotic cells is a challenge of fundamental interest in cell biology. Light microscopy is a powerful tool for observations of the dynamics of live cells, its resolution attainable is limited and insufficient. While electron microscopy can produce images with astonishing resolution and clarity of ultra-thin (<1μm thick) sections of biological specimens, many questions involve the three-dimensional organization of a cell or the interconnectivity of cells. X-ray microscopy offers superior imaging resolution compared to light microscopy, and unique capability of nondestructive three-dimensional imaging of hydrated unstained biological cells, complementary to existing light and electron microscopy.Until now, X-ray microscopes operating in the “water window” energy range between carbon and oxygen k-shell absorption edges have produced outstanding 3D images of cryo-preserved cells. The relatively low X-ray energy (<540eV) of the water window imposes two important limitations: limited penetration (<10μm) not suitable for imaging larger cells or tissues, and small depth of focus (DoF) for high resolution 3D imaging (e.g., ~1μm DoF for 20nm resolution). An X-ray microscope operating at intermediate energy around 2.5keV using Zernike phase contrast can overcome the above limitations and reduces radiation dose to the specimen. Using a hydrated model cell with an average chemical composition reported in literature, we calculated the image contrast and the radiation dose for absorption and Zernike phase contrast, respectively. The results show that an X-ray microscope operating at ~2.5keV using Zernike phase contrast offers substantial advantages in terms of specimen size, radiation dose and depth-of-focus.

X-ray Zernike apodized photon sieves for phase-contrast microscopy

We present a kind of diffractive lens Zernike apodized photon sieves (ZAPS) whose structure is based on the combination of two concepts: apodized photon sieves and Zernike phase-contrast. Combined with the synchrotron light source, the ZAPS can be used as an objective for high-resolution phase-contrast X-ray microscopy in physical and life sciences. The ZAPS is a single optic unit that integrates the appropriate /2 radians phase shift through selective zone placement shifts in an apodized photon sieve. The focusing properties of the ZAPS can be easily controlled by apodizing its pupil function. An apodized photon sieve with Gaussian pupil is fabricated by lithographic technique and shows that the side-lobes are significantly suppressed at the expense of slightly widening the width of the main lobe.

Erratum: “Phase contrast x-ray microscopy study of rabbit primo-vessels” [Appl. Phys. Lett. 97, 213703 (2010)

Author to whom correspondence should be addressed. Electronic mail: shan@jbnu.ac.kr.FIG. 1. a and c The phase contrast x-ray microscopy images of holeson the primo-vessel. b , d , and e are the cross sections of the holes in aand c , respectively. f and h The cross sections of rabbit blood andlymphatic vessels measured in the air, respectively. g and i Schematicsof the blood and lymphatic vessels, respectively.

Phase contrast x-ray microscopy study of rabbit primo vessels

The microstructural properties of the primo-vascular systems of rabbits were examined by phase contrast x-ray microscopy. The primo-vascular systems with an average diameter of 32 μm were extracted from the surfaces of the rabbit internal organs. Phase contrast x-ray imaging showed that the primo-vascular systems were tubules with random holes on their lateral surfaces. The size of the holes on the vascular surface was 2–5 μm. The holes might act as size selective channels for microcells coming in and out and assist in the unidirectional flow of the primo-vascular systems.

Phase-contrast hard X-ray microscopy using synchrotron radiation for the diagnosis of onychomycosis

Onychomycosis, or fungal infection of the nail, is a disease seen frequently in clinical settings. However, the rates of positive identification using potassium hydroxide preparations or fungal cultures are relatively low. Precise diagnosis is possible via histopathologic examination to monitor the existence of fungus and performance of a fungal culture for confirmation. Phase-contrast hard X-ray microscopy using synchrotron radiation provides 70-nm spatial resolution and enables imaging of minute internal cellular structures. This study confirms the feasibility of diagnosing onychomycosis using a phase-contrast hard X-ray microscope developed at 1B2 beam line using a Pohang light source.