Showing papers on "Scanning ion-conductance microscopy published in 2022"

Exploring leakage in dielectric films via automated experiments in scanning probe microscopy

Abstract: Electronic conduction pathways in dielectric thin films are explored using automated experiments in scanning probe microscopy (SPM). Here, we use large field of view scanning to identify the position of localized conductive spots and develop a SPM workflow to probe their dynamic behavior at higher spatial resolution as a function of time, voltage, and scanning process in an automated fashion. Using this approach, we observe the variable behaviors of the conductive spots in a 20 nm thick ferroelectric Hf0.54Zr0.48O2 film, where conductive spots disappear and reappear during continuous scanning. There are also new conductive spots that appear during scanning. The automated workflow is universal and can be integrated into a wide range of microscopy techniques, including SPM, electron microscopy, optical microscopy, and chemical imaging.

Scanning ion-conductance microscopy technique for studying the topography and mechanical properties of Candida parapsilosis yeast microorganisms.

Abstract: Super-resolution microscopy is widely used in the development of novel antimicrobial testing in vitro. In the presented work, a scanning protocol was developed by the method of scanning ion-conducting microscopy (SICM), which makes it possible to study microorganisms without rigid fixation and in saline, obtaining an index map of nanosized structures. The effect of azole and echinocandins drugs on the morphology and mechanical properties of Candida parapsilosis yeast was studied. The findings are consistent with previously proposed drug mechanisms and reports that have examined antifungal agents using AFM, SEM, and TEM. We have shown that the SICM method is capable of scanning and detecting the nanomechanical properties of yeast non-invasively.

In situ microscopic investigation of ion migration on the surface of chromium coated steels

Abstract: Abstract Cathodic spreading of electrolyte on two-layers chromium coatings electrodeposited from trivalent chromium electrolyte on steel was studied on the micro- and the macroscale. The behavior is discussed in view of results obtained on electrical conductivity as measured by current-sensing atomic force microscopy. The coatings were found to hinder electron transport. Heterogeneities observed in the electrical conductivity are correlated to heterogeneities of the electrolyte spreading behavior, studied using in situ scanning Kelvin probe force microscopy. In average, the kinetics of spreading observed at microscopic scales are similar to that observed using a scanning Kelvin probe at larger scales. The scanning Kelvin probe force microscopy is demonstrated as a robust in situ technique to follow electrolyte spreading and study microscopic defects/heterogeneities on the surface.

Co-localizing Kelvin Probe Force Microscopy with Other Microscopies and Spectroscopies: Selected Applications in Corrosion Characterization of Alloys.

Abstract: Kelvin probe force microscopy (KPFM), sometimes referred to as surface potential microscopy, is the nanoscale version of the venerable scanning Kelvin probe, both of which measure the Volta potential difference (VPD) between an oscillating probe tip and a sample surface by applying a nulling voltage equal in magnitude but opposite in sign to the tip-sample potential difference. By scanning a conductive KPFM probe over a sample surface, nanoscale variations in surface topography and potential can be mapped, identifying likely anodic and cathodic regions, as well as quantifying the inherent material driving force for galvanic corrosion. Subsequent co-localization of KPFM Volta potential maps with advanced scanning electron microscopy (SEM) techniques, including back scattered electron (BSE) images, energy dispersive spectroscopy (EDS) elemental composition maps, and electron backscattered diffraction (EBSD) inverse pole figures can provide further insight into structure-property-performance relationships. Here, the results of several studies co-localizing KPFM with SEM on a wide variety of alloys of technological interest are presented, demonstrating the utility of combining these techniques at the nanoscale to elucidate corrosion initiation and propagation. Important points to consider and potential pitfalls to avoid in such investigations are also highlighted: in particular, probe calibration and the potential confounding effects on the measured VPDs of the testing environment and sample surface, including ambient humidity (i.e., adsorbed water), surface reactions/oxidation, and polishing debris or other contaminants. Additionally, an example is provided of co-localizing a third technique, scanning confocal Raman microscopy, to demonstrate the general applicability and utility of the co-localization method to provide further structural insight beyond that afforded by electron microscopy-based techniques.

Scanning Ion Conductance Microscopy and Atomic Force Microscopy: A Comparison of Strengths and Limitations for Biological Investigations

Abstract: AbstractKnowledge of physical properties of cells is vital for many research areas in biology and medicine. Atomic force microscopy (AFM) and scanning ion conductance microscopy (SICM) are two techniques to assess the three-dimensional topography and mechanical properties of cells. This chapter introduces the basic working principles and imaging modes of AFM and SICM and then focuses on their similarities and differences. Strengths and limitations in terms of image resolution, imaging speed, and biomechanical applications are discussed. Also, combined applications of SICM and AFM are highlighted. This chapter shows that SICM has emerged as a major addition to the field of biophysics.KeywordsAFMBiomechanicsCell morphologyHigh-speed imagingResolutionSICM

Sensing Cells-Peptide Hydrogel Interaction In Situ via Scanning Ion Conductance Microscopy

Abstract: Peptide-based hydrogels were shown to serve as good matrices for 3D cell culture and to be applied in the field of regenerative medicine. The study of the cell-matrix interaction is important for the understanding of cell attachment, proliferation, and migration, as well as for the improvement of the matrix. Here, we used scanning ion conductance microscopy (SICM) to study the growth of cells on self-assembled peptide-based hydrogels. The hydrogel surface topography, which changes during its formation in an aqueous solution, were studied at nanoscale resolution and compared with fluorescence lifetime imaging microscopy (FLIM). Moreover, SICM demonstrated the ability to map living cells inside the hydrogel. A zwitterionic label-free pH nanoprobe with a sensitivity > 0.01 units was applied for the investigation of pH mapping in the hydrogel to estimate the hydrogel applicability for cell growth. The SICM technique that was applied here to evaluate the cell growth on the peptide-based hydrogel can be used as a tool to study functional living cells.

Application of Scanning Ion Conductance Microscopy in the Studies of Podocytes Morphological Changes

Abstract: High-resolution imaging of glomerular podocytes morphology is becoming an essential and helpful tool for studying their role in renal disease progression. Electron microscopy (EM) is commonly used to analyze the effacement of the podocytes' cell foot processes and the glomerular filtration barrier integrity loss. However, EM does not allow studying living samples and requires multiple complex procedures for sample preparation. Here, we propose and demonstrate the successful application of Scanning Ion Conductance Microscopy (SICM) for studying morphological changes of cultured podocytes and freshly isolated glomeruli. SICM provides a high-resolution (comparable to EM) non-optical imaging of cell topography using hopping probe microscopy principles and new dynamic reconstruction software. This technique can be used for analysis of cell membrane morphology and different functional characteristics, such as cell volume, membrane potentials, single ion-channel currents, and other parameters. The major advantage of the current method is that it can be applied to live samples with complex morphology, such as intact glomeruli, under physiologically relevant liquid conditions. We have established and demonstrated a successful application of the SICM method in the live human glomerulus and provided a proof of principle for future dynamic analysis of membrane morphology and varied functional parameters in the living glomerulus. As a proof of principle, we applied this method for estimation the pathological structural changes in podocyte foot processes in type 2 diabetic nephropathy (T2DN) rats. Using topographical quantification of the length and irregular shape of the podocyte foot processes, we showed an absence of interdigitated foot processes on the selected region of the glomerular slit diaphragm in isolated T2DN glomeruli. In addition to the application of SICM with freshly isolated glomeruli, we used this approach to visualize and quantify foot process dynamics in cultured human podocytes during pharmacological applications. Thus, we showed that destroying the F-actin with cytochalasin D completely stopped the migration of the podocyte filopodium through the remodeling of the actin cytoskeleton. Here, we further applied SICM to detect morphological changes in human podocytes after activation of Protease-activated receptor-1 (PAR1) by acute application of agonist TFLLR-NH2 . A series of experiments revealed that PAR1 activation led to retraction of the lamellipodium and a significant decrease in cell surface area (+51±46 vs. -15±8 µm2 , 30 min after application of vehicle or TFLLR, respectively; n=5, p<0.05). In summary, SICM has numerous advantages and has excellent potential for precise quantitative analyses of the morphological changes in the glomerulus and cultured podocytes. Moreover, it opens the possibility of performing patch-clamp recordings on the specific parts of the podocyte cell body and advances our understanding of the function and mechanism of the glomerulus filtration barrier.

Methods for Accuracy Increasing of Solid Brittle Materials Fracture Toughness Determining

Abstract: Method for determining of the fracture toughness of brittle materials by indentation is described. The critical stress intensity factor KIC quantifies the fracture toughness. Methods were developed and applied to improve the accuracy of KIC determination due to atomic force microscopy and nanoindentation. It is necessary to accurately determine parameters and dimensions of the indentations and cracks formed around them in order to determine the KIC . Instead of classical optical and scanning electron microscopy an alternative high-resolution method of atomic force microscopy was proposed as an imaging method.Three methods of visualization were compared. Two types of crack opening were considered: along the width without vertical displacement of the material and along the height without opening along the width. Due to lack of contact with the surface of the samples under study, the methods of optical and scanning electron microscopy do not detect cracks with a height opening of less than 100 nm (for optical) and less than 40–50 nm (for scanning electron microscopy). Cracks with opening in width are determined within their resolution. Optical and scanning electron microscopy cannot provide accurate visualization of the deformation area and emerging cracks when applying small loads (less than 1.0 N). The use of atomic force microscopy leads to an increase in accuracy of determining of the length of the indent diagonal up to 9.0 % and of determining of the crack length up to 100 % compared to optical microscopy and up to 67 % compared to scanning electron microscopy. The method of atomic force microscopy due to spatial three-dimensional visualization and high accuracy (XY ± 0.2 nm, Z ± 0.03 nm) expands the possibilities of using indentation with low loads.A method was proposed for accuracy increasing of KIC determination by measuring of microhardness from a nanoindenter. It was established that nanoindentation leads to an increase in the accuracy of KIC determination by 16–23 % and eliminates the formation of microcracks in the indentation.