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Abstract: The butterfly wing scales are biocomposites with impressive structural and optical properties, owing to their features spanning from hundreds of microns to a few nanometers. Though they demonstrate efficient color production and structural rigidity, the mechanisms to achieve them are well-concealed across different length scales. As a result, understanding these biocomposites' composition, structure, and corresponding function remains challenging. No single technique can provide a high-resolution three-dimensional (3D) volume with an accurate color map. Traditionally, approaches such as light microscopy (LM) and spectrophotometry for color responses, and scanning electron microscopes (SEM) and transmission electron microscopes (TEM) for structural imaging provide key insights. However, these methods offer either limited resolution (LM) or limited field of view (TEM), falling short of capturing the full complexity of the scales. Here, we used ptychographic X-ray computed tomography (PXCT), which provides 3D density maps at an intermediate resolution (66.5nm) over hundreds of microns. This allowed us to combine the inferences from the high-resolution (<1 nm), limited view structural insights from TEM/SEM with the low-resolution (>1 microm) color response from LM/spectrophotometry. In Figure 1, the images obtained from various modalities are shown along with their corresponding length scales. Notably, PXCT provides both 3D structural measurements and density values. The 3D structural measurements enable us to estimate the tilt map of the continuous lower lamina structure of the scale and the thickness map of the intricate upper lamina structure. The known physics behind the reflectance and absorbance spectra enables us to combine insights from a wide range of imaging modalities synergistically. An optical model estimates reflectance spectra by integrating thickness and tilt information from PXCT and sub-layer separation insights from the resin section TEM. This computational scheme iteratively solves for the refractive indices of the scale layers from the experimentally measured reflectance spectra. Further, such correlative modeling provides the reflectance map of the scale (Fig. 2), which explains the spatial colour variation (adwing) and the influence of the upper lamina in diffusing the color (abwing). In addition, the 3D thickness map of the upper lamina is utilized to get the absorption coefficient of the upper and the lower lamina from the measured absorbance spectra. The absorption coefficient values showed that the upper and lower lamina have similar pigment densities. This work demonstrates that a multi-modal imaging approach, integrating computational and optical modeling, can reveal unique and novel insights into biocomposites that cannot be possible with any single imaging method alone.

Open Access

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Abstract: Although the LiCoO2 (LCO) cathode material has been widely used in commercial lithium ion batteries (LIB) and shows high stability, LIB’s improvements have several challenges that still need to be overcome. In this paper, we have studied the in-operando structural properties of LCO within battery cells using Bragg Coherent X-ray Diffraction Imaging to identify ways to optimise the LCO batteries’ cycling. We have successfully reconstructed the X-ray scattering phase variation (a fingerprint of atomic displacement) within a ≈ (1.6 × 1.4 × 1.3) μm3 LCO nanocrystal across a charge/discharge cycle. Reconstructions indicate strained domains forming, expanding, and fragmenting near the surface of the nanocrystal during charging, with a determined maximum relative lattice displacements of 0.467 Å. While discharging, all domains replicate in reverse the effects observed from the charging states, but with a lower maximum relative lattice displacements of 0.226 Å. These findings show the inefficiency-increasing domain dynamics within LCO lattices during cycling.

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Abstract: Promotion of oxygen reduction reaction (ORR) kinetics, to a large extent, depends on the rational modulation of the electronic structure and mass diffusion of electrocatalysts. Herein, a ferrocene (Fc)–assisted strategy is developed to prepare Fc-trapped ZnMo–hybrid zeolitic imidazolate framework (Fc@ZnMo-HZIF-50) and the derived Fe single atom coupling with MoC nanoparticles, coembedded in hierarchically porous N-doped carbon cubes (MoC@FeNC-50). The introduced Fc is utilized not only as an iron source for single atoms but also as a morphology regulator for generating a hierarchically porous structure. The redistribution of electrons between Fe single atoms and MoC nanoparticles effectively promotes the adsorption of O2 and the formation of *OOH intermediates during the ORR process. Along with a 3D hierarchically porous architecture for enhanced mass transport, the as-fabricated MoC@FeNC-50 presents excellent activity (E1/2 = 0.83 V) and durability (only 9.5% decay in current after 40000 s). This work could inspire valuable insights into the construction of efficient electrocatalysts through electron configuration and kinetics engineering.

Open Access

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Abstract: X-ray ptychography, a scanning coherent diffraction imaging technique, is one of the most used techniques at synchrotron facilities for high resolution imaging, with applications spanning from life science to nano-electronics. In the recent years there has been a great effort to make the technique faster to enable high throughput nanoscale imaging. Here we apply a fast ptychography scanning method to image in 3D μ of brain-like phantom at 3 kHz, in a 7 h acquisition with a resolution of 270 nm. We then present the latest advances in fast ptychography by showing 2D images acquired at 110 kHz by combining the fast-acquisition scheme with a high-acquisition rate prototype detector from DECTRIS Ltd. We finally review the experimental outcome and discuss the prospective use of fast ptychography schemes for the investigation of mm size samples of brain-like phantom, by extrapolating the current results to the high coherent flux scenario of diffraction limited storage rings.

Open Access

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Abstract: Isolation of tissue-specific fetal stem cells and derivation of primary organoids is limited to samples obtained from termination of pregnancies, hampering prenatal investigation of fetal development and congenital diseases. Therefore, new patient-specific in vitro models are needed. To this aim, isolation and expansion of fetal stem cells during pregnancy, without the need for tissue samples or reprogramming, would be advantageous. Amniotic fluid (AF) is a source of cells from multiple developing organs. Using single-cell analysis, we characterized the cellular identities present in human AF. We identified and isolated viable epithelial stem/progenitor cells of fetal gastrointestinal, renal and pulmonary origin. Upon culture, these cells formed clonal epithelial organoids, manifesting small intestine, kidney tubule and lung identity. AF organoids exhibit transcriptomic, protein expression and functional features of their tissue of origin. With relevance for prenatal disease modeling, we derived lung organoids from AF and tracheal fluid cells of congenital diaphragmatic hernia fetuses, recapitulating some features of the disease. AF organoids are derived in a timeline compatible with prenatal intervention, potentially allowing investigation of therapeutic tools and regenerative medicine strategies personalized to the fetus at clinically relevant developmental stages.