Phase Contrast Mode Research Articles

Multi-scale fractal Fourier Ptychographic microscopy to assess the dose-dependent impact of copper pollution on living diatoms

Accumulation of bioavailable heavy metals in aquatic environment poses a serious threat to marine communities and human health due to possible trophic transfers through the food chain of toxic, non-degradable, exogenous pollutants. Copper (Cu) is one of the most spread heavy metals in water, and can severely affect primary producers at high doses. Here we show a novel imaging test to assay the dose-dependent effects of Cu on live microalgae identifying stress conditions when they are still capable of sustaining a positive growth. The method relies on Fourier Ptychographic Microscopy (FPM), capable to image large field of view in label-free phase-contrast mode attaining submicron lateral resolution. We uniquely combine FPM with a new multi-scale analysis method based on fractal geometry. The system is able to provide ensemble measurements of thousands of diatoms in the liquid sample simultaneously, while ensuring at same time single-cell imaging and analysis for each diatom. Through new image descriptors, we demonstrate that fractal analysis is suitable for handling the complexity and informative power of such multiscale FPM modality. We successfully tested this new approach by measuring how different concentrations of Cu impact on Skeletonema pseudocostatum diatom populations isolated from the Sarno River mouth.

Efficacy of polyacrylate latex nanodispersions as consolidation agents in porous sandstones evaluated by synchrotron X-ray computed microtomography

This research describes the effects of two innovative aqueous polyacrylate polymers on the microstructure of porous stone materials. Such latex nanodispersions have been designed (with and without fluorination) as consolidation agents and tested on two types of sandstone, namely, Prague (Mšené) and Obernkirchen, largely used as building materials for valuable Cultural Heritage objects. Quantitative description of the polymer distribution within the specimens was obtained noninvasively by adopting synchrotron radiation computed microtomography. The propagation-based phase-contrast mode was adopted to test its effectiveness in enabling the recognition of the polymers in the two matrices, which is usually hampered by their low attenuation coefficient for X-rays. Quantitative image analysis revealed significant dissimilarities in total porosity, specific surface area of pores, connectivity density and fractal dimension as a consequence of the consolidation treatments. For instance, about 7% and 3% lower porosity values were found in the consolidated Prague and Obernkirchen sandstones, respectively, with the distribution shifted towards smaller pores. Furthermore, the simulation of water transport, based on the retrieved pore network, evidenced a decrease in water permeability and diffusivity of more than one order of magnitude in the treated samples; the effect was more pronounced along the direction of penetration of the consolidating agent. Overall, both latexes exhibited similar film-forming and pore-filling abilities. In general, the results highlighted the high potential of synchrotron-based 3D X-ray imaging for the quantitative assessments of the porous microstructure of consolidated building materials.

High energy x-ray Talbot-Lau interferometer employing a microarray anode-structured target source to extend the field of view.

High energy and large field of view (FOV) phase contrast imaging is crucial for biological and even medical applications. Although some works have devoted to achiving a large field of view at high energy through bending gratings and so on, which would be extremely challenging in medical high energy imaging. We analyze the angular shadowing effect of planar gratings in high-energy X-ray Talbot-Lau interferometer (XTLI). Then we design and develop an inverse XTLI coupled with a microarray anode-structured target source, to extend the FOV at high energy. Our experimental results demonstrate the benefit of the source in inverse XTLI and a large FOV of 106.6 mm in the horizontal direction is achieved at 40 keV. Based on this system, experiments of a mouse demonstrate the potential advantage of phase contrast mode in imaging lung tissue. We extend the FOV in a compact XTLI using a microarray anode-structured target source coupled with an inverse geometry, which eliminates grating G0 and relaxes the fabrication difficulty of G2. We believe the established design idea and imaging system would facilitate the wide applications of XTLI in high energy phase contrast imaging.

Transmission mode synthetic aperture interferometry using a compact coherent imager and switched fiber-optic illumination

This paper discusses a modular implementation of synthetic aperture interferometry (SAI) using inexpensive telecommunications technologies that can be expanded for use in optical instruments with arbitrarily large fields of view. Exploiting multiple image sensors and multiple illumination sources, transmission and reflection SAI geometries, capable of emulating the phase contrast and interference modes of conventional interference microscopes, are considered. The point-spread and transfer characteristics of these geometries are illustrated for the case of a transmission mode instrument. It is shown that although imaging is strictly field dependent (i.e. shift-variant), the response of modular instruments is periodic and with careful choice of illumination and sensor positioning can be made quasi shift-invariant. We demonstrate SAI in a transmission configuration comprising of a single coherent imager that holographically records the field scattered from a test target sequentially illuminated by 16 different plane waves. This set-up is equivalent to a single module of a larger SAI system and since brightfield regions in the individual reconstructed images overlap, provides an ideal platform to examine the effect of tilt and phase offset errors in the illumination. By applying a first order correction and assuming phase continuity over the overlapping regions, we demonstrate a significant improvement in the SAI reconstruction.

A versatile laboratory setup for high resolution X-ray phase contrast tomography and scintillator characterization.

X-ray micro-tomography (μCT) is a powerful non-destructive 3D imaging method applied in many scientific fields. In combination with propagation-based phase-contrast, the method is suitable for samples with low absorption contrast. Phase contrast tomography has become available in the lab with the ongoing development of micro-focused tube sources, but it requires sensitive and high-resolution X-ray detectors. The development of novel scintillation detectors, particularly for microscopy, requires more flexibility than available in commercial tomography systems. We aim to develop a compact, flexible, and versatile μCT laboratory setup that combines absorption and phase contrast imaging as well as the option to use it for scintillator characterization. Here, we present details on the design and implementation of the setup. We used the setup for μCT in absorption and propagation-based phase-contrast mode, as well as to study a perovskite scintillator. We show the 2D and 3D performance in absorption and phase contrast mode, as well as how the setup can be used for testing new scintillator materials in a realistic imaging environment. A spatial resolution of around 1.3μm is measured in 2D and 3D. The setup meets the needs for common absorption μCT applications and offers increased contrast in phase contrast mode. The availability of a versatile laboratory μCT setup allows not only for easy access to tomographic measurements, but also enables a prompt monitoring and feedback beneficial for advances in scintillator fabrication.

Visualization of Water Distribution in Fuel Cell Microporous and Catalyst Layers with 3D Nanoscale X-Ray Imaging

As an efficient green energy technology, polymer electrolyte membrane fuel cells (PEMFCs) are rapidly growing in a wide range of applications. Development of high power-density PEMFCs is under investigation to further reduce the overall cost and footprint. However, in such operational conditions, excessive water production could restrict the transport of reactants due to flooding, and subsequently degrade the performance of the PEMFC. This makes the water management a major challenge and necessitates a good understanding of water distribution and transport within the porous layers of the PEMFC [1, 2].3D X-ray computed tomography (XCT) is a strong tool for visualizing the water distribution within porous media. Micro-scale XCT has shown great promise in understanding and visualizing the water behavior within the gas diffusion layer (GDL) substrate region possessing ~10-100 µm pores [3–6]. This resolution, however, is not sufficient to capture water distribution in microporous and catalyst layers (MPL and CL), which are predominantly composed of nano-scale pores. This work aims to explore a method of water capture and visualization within the MPL and CL of a PEMFC using a lab-based nano-resolution XCT (NXCT) with a spatial resolution as high as 50 nm. Benefitting from the non-invasive NXCT imaging technique, the same spot of a dry/wet material has been studied in Zernike phase contrast mode using a custom-built enclosed fixture with high X-ray throughput to maintain a constant humidity (100% RH) over the tomographic acquisition period. Water domains have been identified after alignment of wet and dry image data sets followed by subtraction of dry from wet data set. Figure 1a shows a 2D projection of the MPL on AvCarb GDL after vacuum-assisted water infiltration. A gold microsphere is fixed on the sample within a thin layer of epoxy to allow for accurate identification of the region of interest. Figure 1b shows a selected segmented 2D projection of wet MPL illustrating how liquid water clusters are distributed within the pores and the 3D volume rendering of structural features is displayed in Figure 1c. Using the above-described method, 18% and ~7% volume fraction of liquid water has been identified within the wetted MPL and CL, respectively. The methodology discussed here is a step toward deep understanding of water transport phenomena in CL and MPL materials dictating the strategies for materials design to prevent flooding under high current densities. Moreover, the set-up and methodology can be further optimized to visualize water domains under controlled temperature and relative humidity, to simulate the real operating conditions. Figure 1. XCT imaging of a wet MPL: (a) A radiograph of MPL on AvCarb GDL after vacuum-assisted water infiltration; (b) a selected 2D projection of MPL showing the segmented solid (green), liquid water (blue), and unoccupied pores (black) domains; and (c) 3D volume rendering of a subdomain in the MPL showing the distribution of liquid water within the pores of the structure (voxel size 32 nm in b and c). Acknowledgement Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada, Ballard Power Systems, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, and Canada Research Chairs.

Single-particle cryo-EM structures from iDPC–STEM at near-atomic resolution

In electron cryomicroscopy (cryo-EM), molecular images of vitrified biological samples are obtained by conventional transmission microscopy (CTEM) using large underfocuses and subsequently computationally combined into a high-resolution three-dimensional structure. Here, we apply scanning transmission electron microscopy (STEM) using the integrated differential phase contrast mode also known as iDPC–STEM to two cryo-EM test specimens, keyhole limpet hemocyanin (KLH) and tobacco mosaic virus (TMV). The micrographs show complete contrast transfer to high resolution and enable the cryo-EM structure determination for KLH at 6.5 Å resolution, as well as for TMV at 3.5 Å resolution using single-particle reconstruction methods, which share identical features with maps obtained by CTEM of a previously acquired same-sized TMV data set. These data show that STEM imaging in general, and in particular the iDPC–STEM approach, can be applied to vitrified single-particle specimens to determine near-atomic resolution cryo-EM structures of biological macromolecules.

Linear imaging theory for differential phase contrast and other phase imaging modes in scanning transmission electron microscopy

We propose a linear imaging theory for differential phase contrast under the weak-phase-weak-amplitude object approximation. Contrast transfer functions are defined for thin and thick weak objects, and they successfully describe several imaging characteristics of differential phase contrast. We discuss the defocus dependence of the contrast for several examples: atomic resolution, a p-n junction, a heterointerface, and grain boundaries. Understanding the imaging characteristics helps in adjusting aberrations in DPC STEM.

Construction of A Model Used for Mechanisms of the Antitumoral Effects of Traditional Chinese Medicine Compounds Using A High-content Imaging System

Objective: To construct a high-content imaging system analysis model to study the effects of the traditional Chinese medicine compounds puerarin on proliferation and migration of cervical cancer (HeLa) cells. Methods: The digital phase-contrast mode unique to the high-content imaging system was used to study the proliferation and migration effects of puerarin on HeLa cells. Results: Puerarin inhibited HeLa cell proliferation and migration. The high-content analysis model constructed in this study enabled efficiently and accurately determining cell proliferation and migration parameters in batches and allowed detecting multiple phenotypic parameters in one experiment. These parameters provide a theoretical basis for subsequent research. Conclusion: Puerarin inhibited HeLa cell proliferation and migration. The high-content analysis model constructed in this study uses a digital phase-contrast mode rather than traditional fluorescence staining and cell scratch tests for label-free analysis, thus providing a more rapid, efficient and accurate analysis method for tumor research.

Membrane Pd–7.70 wt % Lu Alloy for the Preparation and Purification of Hydrogen

The purity of hydrogen, which is an alternative energy carrier in powder sources of distributed energy resource systems and, in particular, is the feed stock for fuel cells, should be no less than 99.9999 vol % purity High-purity hydrogen can be prepared only via its separation as a result of selective diffusion through metallic membranes manufactured from specific membrane palladium-based alloys prepared in the form of thin foils. In the present work, the combination of deformation and annealings under different conditions is used to prepare the Pd–7.70 wt % Lu alloy in the form of foil 50 µm thick, whose specific hydrogen permeability is studied in the course of cyclic heating and cooling in a hydrogen atmosphere in a temperature range of 300–500°С. The Pd–7.70 wt % Lu membrane is shown to demonstrate high and stable hydrogen permeability. The evolution of the surface structure of the membrane in the course of its operation in the hydrogen atmosphere is studied by atomic force microscopy using the phase contrast mode.

Multiplane differential phase contrast imaging using asymmetric illumination in volume holographic microscopy.

.Significance: Differential phase contrast (DPC) is a well-known imaging technique for phase imaging. However, simultaneously acquiring multidepth DPC images is a non-trivial task. We propose simultaneous multiplane DPC imaging using volume holographic microscopy (VHM).Aim: To design and implement a new configuration of DPC-VHM for multiplane imaging.Approach: The angularly multiplexed volume holographic gratings (AMVHGs) and the wavelength-coded volume holographic gratings (WC-VHGs) are used for this purpose. To obtain asymmetric illumination for DPC images, a dynamic illumination system is designed by modifying the regular Köhler illumination using a thin film transistor panel (TFT-panel).Results: Multidepth DPC images of standard resolution chart and biosamples were used to compare imaging performance with the corresponding bright-field images. An average contrast enhancement of around three times is observed for target resolution chart by DPC-VHM. Imaging performance of our system is studied by modulation transfer function analysis, which suggests that DPC-VHM not only suppresses the DC component but also enhances high-frequency information.Conclusions: Proposed DPC-VHM can acquire multidepth-resolved DPC images without axial scanning. The illumination part of the system is adjustable so that the system can be adapted to bright-field mode, phase contrast mode, and DPC mode by controlling the pattern on the TFT-panel.

Synchrotron microtomography applied to the volumetric analysis of internal structures of Thoropa miliaris tadpoles

Amphibians are models for studying applied ecological issues such as habitat loss, pollution, disease, and global climate change due to their sensitivity and vulnerability to changes in the environment. Developmental series of amphibians are informative about their biology, and X-ray based 3D reconstruction holds promise for quantifying morphological changes during growth—some with a direct impact on the possibility of an experimental investigation on several of the ecological topics listed above. However, 3D resolution and discrimination of their soft tissues have been difficult with traditional X-ray computed tomography, without time-consuming contrast staining. Tomographic data were initially performed (pre-processing and reconstruction) using the open-source software tool SYRMEP Tomo Project. Data processing and analysis of the reconstructed tomography volumes were conducted using the segmentation semi-automatic settings of the software Avizo Fire 8, which provide information about each investigated tissues, organs or bone elements. Hence, volumetric analyses were carried out to quantify the development of structures in different tadpole developmental stages. Our work shows that synchrotron X-ray microtomography using phase-contrast mode resolves the edges of the internal tissues (as well as overall tadpole morphology), facilitating the segmentation of the investigated tissues. Reconstruction algorithms and segmentation software played an important role in the qualitative and quantitative analysis of each target structure of the Thoropa miliaris tadpole at different stages of development, providing information on volume, shape and length. The use of the synchrotron X-ray microtomography setup of the SYRMEP beamline of Elettra Synchrotron, in phase-contrast mode, allows access to volumetric data for bone formation, eye development, nervous system and notochordal changes during the development (ontogeny) of tadpoles of a cycloramphid frog Thoropa miliaris. As key elements in the normal development of these and any other frog tadpole, the application of such a comparative ontogenetic study, may hold interest to researchers in experimental and environmental disciplines.

A correlation analysis of Light Microscopy and X-ray MicroCT imaging methods applied to archaeological plant remains\u2019 morphological attributes visualization

In this work, several attributes of the internal morphology of drupaceous fruits found in the archaeological site Monte Castelo (Rondonia, Brazil) are analyzed by means of two different imaging methods. The aim is to explore similarities and differences in the visualization and analytical properties of the images obtained via High Resolution Light Microscopy and X-ray micro-computed tomography (X-ray MicroCT) methods. Both provide data about the three-layered pericarp (exo-, meso- and endocarp) of the studied exemplars, defined by cell differentiation, vascularisation, cellular contents, presence of sclerenchyma cells and secretory cavities. However, it is possible to identify a series of differences between the information that can be obtained through each of the methods. These variations are related to the definition of contours and fine details of some characteristics, their spatial distribution, size attributes, optical properties and material preservation. The results obtained from both imaging methods are complementary, contributing to a more exhaustive morphological study of the plant remains. X-ray MicroCT in phase-contrast mode represents a suitable non-destructive analytic technique when sample preservation is required.

Shedding Light on Metal-Based Nanoparticles in Zebrafish by Computed Tomography with Micrometer Resolution.

Metal-based nanoparticles are clinically used for diagnostic and therapeutic applications. After parenteral administration, they will distribute throughout different organs. Quantification of their distribution within tissues in the 3D space, however, remains a challenge owing to the small particle diameter. In this study, synchrotron radiation-based hard X-ray tomography (SRμCT) in absorption and phase contrast modes is evaluated for the localization of superparamagnetic iron oxide nanoparticles (SPIONs) in soft tissues based on their electron density and X-ray attenuation. Biodistribution of SPIONs is studied using zebrafish embryos as a vertebrate screening model. This label-free approach gives rise to an isotropic, 3D, direct space visualization of the entire 2.5 mm-long animal with a spatial resolution of around 2 µm. High resolution image stacks are available on a dedicated internet page (http://zebrafish.pharma-te.ch). X-ray tomography is combined with physico-chemical characterization and cellular uptake studies to confirm the safety and effectiveness of protective SPION coatings. It is demonstrated that SRμCT provides unprecedented insights into the zebrafish embryo anatomy and tissue distribution of label-free metal oxide nanoparticles.

High-aspect ratio probes with selected geometry for advanced MFM measurements

Probes with high aspect ratio Pt/C nanowhiskers on the tops of Si cantilevers coated with a thin magnetic layer were fabricated. A simulation of the magnetic field strength gradient in the interaction of single magnetic domains with probes of various shapes is carried out. The optimal parameters of magnetic field detection were found, such as the probe geometry, material and thickness of the magnetic coating. The quality of domain visualization in the phase contrast mode for both types of probes was compared. An improvement of phase contrast with nanowhiskers probes was confirmed by consistent experimental and simulation data.

Development of Physical Breast Phantoms for X-ray Imaging Employing 3D Printing Techniques

Objective: This study aims to investigate the use of 3D printing techniques for the fabrication of physical breast phantoms, suitable for conventional and phase contrast breast imaging. Such phantoms could provide essential information for the design, development and optimization of emerging X-ray imaging modalities. Materials and Methods: Physical phantoms were constructed using two 3D printing techniques: Fused Deposition Modeling and Stereolithography. Eight materials suitable for 3D printing, including thermoplastic filaments and photopolymer resins, were investigated for the optimal representation of breast tissues, based on their attenuation and refractive characteristics. The phantoms consisted of a 3D-printed mold, which was then manually filled with paraffin wax. Additionally, a 3D complex-patterned layer and details representing abnormalities were embedded in different depths. Images of the phantoms were obtained in attenuation and phase contrast mode. Experiments were conducted using an X-ray microfocus tube with Tungsten anode set to 55kVp, combined with a photon-counting detector. The distance between source and detector was 56.5cm. The images were acquired at different object-to-detector distances starting from 5cm up to 40cm in a free space propagation set-up. Results and Conclusion: Results show that among all combinations with paraffin used as an adipose substitute, phantoms created with the Stereolithography technique and resins (especially Flex) as glandular equivalent, were found to be more appropriate for both attenuation and phase contrast imaging. The edge enhancement effect was well observed in the experimental images acquired at 35cm object-to-detector distance, indicating the potential for improved feature visualization using this set-up in phase contrast compared to attenuation mode.

Heteroprotein complex of soy protein isolate and lysozyme: Formation mechanism and thermodynamic characterization

The electrostatic assembly between heteroproteins is one of the most important applications of associative interaction. The present study investigated the effects of pH and NaCl on the formation rules, phase behavior, and thermodynamic changes of soy protein isolate (SPI)/lysozyme (LYS) complexes. The hydrodynamic diameter of SPI significantly increased as pH was lowered to 6.5, whereas that of LYS significantly increased at pH ≥ 7.5, as a result of self-aggregation. Electrostatic assembly between SPI and LYS completely complies with the charge compensation, producing nanoscale (about 200 nm) and microscale (about 5 μm) complexes at different mixing ratio. However, NaCl can lower ζ-potential of SPI and LYS, and weaken the electrostatic interaction between heteroproteins. The presence of 200 mM NaCl can completely inhibit the electrostatic assembly between SPI and LYS (1 mg/mL). Not only electrostatic interactions but also hydrogen bonds participated in the complex. As the observation of phase-contrast mode, the pH, stoichiometry, NaCl, and assembling time significantly affected size and shape of SPI/LYS complexes, whereas all SPI/LYS complexes exhibited solid-liquid phase separation on the time scale of 0–60 min. Isothermal titration calorimetry analysis indicated that SPI/LYS complex was thermodynamically favored (ΔG < 0), both the exotherm (ΔH < 0) and the entropy gain contributed to SPI/LYS assembling while the entropy gain might be the dominant term. Moreover, the absolute values of ΔG, ΔH, and ΔS significantly decreased with increasing NaCl concentration.

Growth-related micromorphological characteristics of the porcine common carotid artery.

The purpose of this study was to gain knowledge about the micromorphology of the porcine common carotid artery (CCA) during the period of growth over the bodyweight range of 10-40kg. CCA samples from German landrace pigs (DL) aged either 2 or 3months (DL-2 and DL-3) were compared with samples from Göttingen minipigs (GM) aged either 18 or 40months (GM-18 and GM-40) using transmitted light (phase-contrast mode) and transmission electron microscopy. The GM-18, GM-40 and the DL-3 groups had typical muscular artery histological characteristics. Contrasting to this, the 2-month-old DL pigs had a transitional artery type being characterized by a significantly higher proportion of elastic fibres and a significantly lower number of smooth muscle cells than did the 1month older DL-3. During the period of maturation, the tunica media of the CCA in GM animals thickened by 1.3× and in DL animals by 2.5× resulting in an overall increased vessel wall thickness. The cumulated thickness of the tunica interna (endothelium, stratum subendotheliale and internal elastic lamina) and the tunica media (including the external elastic lamina) of DL-3 and GM-40 pigs were similar to each other and comparable to that of humans. With an increasing vessel wall thickness, the luminal diameter decreased in GM by 19% and in DL by 11%. Additionally, in the older age groups, GM-40 and DL-3, the internal elastic lamina principally was continuous, but there were also interrupted large segments of elastic lamina separated by gaps. In addition, the principal internal elastic lamina was duplicated in several places.

Mineralization pathways in the active murine epiphyseal growth plate

Endochondral ossification in the growth plate of long bones involves cartilage mineralization, bone formation and the budding vasculature. Many of these processes take place in a complex and dynamic zone, the provisional ossification zone, of the growth plate. Here we investigate aspects of mineralization in 2D and 3D in the provisional ossification zone at different length scales using samples preserved under cryogenic or fully hydrated conditions. We use confocal light microscopy, cryo-SEM and micro-CT in the phase contrast mode. We show in 9 week old BALB/c mice the presence of vesicles containing mineral particles in the blood serum, as well as mineral particles without membranes integrated with the blood vessel walls. We also observe labeled mineral particles within cells associated with bone formation, but not in the hypertrophic cartilage cells that are involved with cartilage mineralization. High resolution micro-CT images of fresh hydrated tibiae, show that there are open continuous pathways between the blood vessel extremities and the hypertrophic chondrocyte zone. As the blood vessel extremities, the mineralizing cartilage and the forming bone are all closely associated within this narrow zone, we raise the possibility that in addition to ion transport, mineral necessary for both cartilage and bone formation is also transported through the vasculature.

Humidity-Dependent Surface Structure and Hydroxide Conductance of a Model Quaternary Ammonium Anion Exchange Membrane

Anion exchange membrane (AEM) fuel cells (AEMFCs) are a promising cost-effective alternative energy conversion technology because of the potential implementation of earth-abundant catalysts, obviating the need for precious metals. AEMs, however, have low conductivity and suffer from poor stability. The conductivity of the AEM is inherently tied to the complex phase-separated morphology, as its dependence on the hydration level is not well understood. In this report, we employ phase-contrast tapping mode and conductive-probe atomic force microscopy (cp-AFM) to study the nanoscale surface morphology and hydroxide conductance of a commercially available quaternary ammonium (QA) AEM by FuMA-Tech GmbH (Fumapem FAA-3). The chemical structure of FAA-3 consists of a poly(phenylene oxide) backbone with QA functionality. The morphology of FAA-3 was observed in the bromide (FAA-3-Br-) and hydroxide form (FAA-3-OH-) in dehydrated and hydrated conditions. Under dehydrated conditions, both membranes showed no phase contrast, indicating the absence of phase-separated hydrophilic domains at the surface. At hydrated conditions, FAA-3-Br- shows randomly dispersed isolated clusters, while FAA-3-OH- shows elongated fibrillar structures extending microns in length. cp-AFM of hydrated FAA-3-OH- showed that these elongated regions were insulating. These results provide morphological evidence for the conduction of hydroxide at the surface and its dependence on the hydration level.