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Electrochemical impedance spectroscopy (EIS) is widely used for battery cell testing in industrial production and R&D labs. This work addresses the use of EIS calibration and uncertainty analysis in cell classification. Five scenarios are investigated to discuss qualitatively the impact of calibration and uncertainty on classification. For an experimental demonstration, a cylindrical cell was measured with two mechanical fixtures of different qualities and characterized regarding random errors and calibrated impedances. The impact of uncertainty and impedance calibration on the cell classification is shown, and based on the uncertainty and corresponding error bounds, a confidence level was established for the classification results. Quantitative uncertainty bounds are presented for the full EIS frequency spectrum ranging from 150 mHz to 5 kHz.

Electrochemical impedance spectroscopy (EIS) is a widely used method for battery tests in manufacturing and automotive field applications. As such, accurate measurement of the impedance over a broad frequency spectrum is of high relevance, also requiring specific calibration methods and evaluation of error bounds. Here, we report for the first time a comprehensive uncertainty analysis of calibrated EIS for batteries. We aim to identify two uncertainty sources, the fixture repeatability and measurement noise, and evaluate their effect on the measured impedances. To this end, an error model assigned to each of them and the real and imaginary parts of the model parameters are characterized in the frequency range of 100 mHz–5 kHz by performing specific impedance measurements on a shunt resistor and a short standard. We demonstrate how different uncertainties are combined with the measured impedances, incorporating also the impedance calibration procedure. The errors are propagated through the calibration and correction functions by applying the linear error propagation method provided by the UncLib package from METAS. The error bounds are derived from uncertainty propagation in the shunt standard and the prismatic battery cell EIS and verified by conducting a series of measurements. Thereby, the uncertainty is shown as ellipsoids in every frequency point of the Nyquist plot. For instance, at 1 Hz, the 34-Ah prismatic cell shows a calibrated real-part impedance and two standard deviation error bounds of 1.07mΩ±26μΩ.

We have demonstrated the capabilities of the scanning microwave microscopy (SMM) technique for measuring ferromagnetic resonance (FMR) spectra in nanometric areas of magnetic samples. The technique is evaluated using three different samples, including a yttrium iron garnet (YIG) polycrystalline bulk sample and a thick YIG film grown by liquid phase epitaxy (LPE). Patterned permalloy (Py) micromagnetic dots have been characterized to assess the performance for imaging applications of the technique, measuring the variation of the magnetic properties of the sample along its surface. The proposed technique may pave the way for the development of high spatially resolved mapping of magnetostatic modes in different nanomagnetic and micromagnetic structures.\ud

The operational stability of organic-inorganic halide perovskite based solar cells is a challenge for widespread commercial adoption. The mobility of ionic species is a key contributor to perovskite instability since ion migration can lead to unfavourable changes in the crystal lattice and ultimately destabilisation of the perovskite phase. Here we study the nanoscale early-stage degradation of mixed-halide mixed-cation perovskite films under operation-like conditions using electrical scanning probe microscopy to investigate the formation of surface nanograin defects. We identify the nanograins as lead iodide and study their formation in ambient and inert environments with various optical, thermal, and electrical stress conditions in order to elucidate the different underlying degradation mechanisms. We find that the intrinsic instability is related to the polycrystalline morphology, where electrical bias stress leads to the build-up of charge at grain boundaries and lateral space charge gradients that destabilise the local perovskite lattice facilitating escape of the organic cation. This mechanism is accelerated by enhanced ionic mobility under optical excitation. Our findings highlight the importance of inhibiting the formation of local charge imbalance, either through compositions preventing ionic redistribution or local grain boundary passivation, in order to extend operational stability in perovskite photovoltaics.

This co-creation workshop event was organised by the H2020 project NanoMECommonswith the support of the European Materials Modelling Council (EMMC ASBL)and the European Materials Characterisation Council (EMCC).

An electrochemical quartz crystal microbalance (EC-QCM) is a versatile gravimetric technique that allows for parallel characterization of mass deposition and electrochemical properties. Despite its broad applicability, simultaneous characterization of two electrodes remains challenging due to practical difficulties posed by the dampening from fixture parasitics and the dissipative medium. In this study, we present a dual electrochemical QCM (dual EC-QCM) that is employed in a three-electrode configuration to enable consequent monitoring of mass deposition and viscous loading on two crystals, the working electrode (WE) and the counter electrode (CE). A novel correction approach, along with a three standard complex impedance calibration, is employed to overcome the effect of dampening while keeping high spectral sensitivity. Separation of viscous loading and rigid mass deposition is achieved by robust characterization of the complex impedance at the resonance frequency. Validation of the presented system is done by cyclic voltammetry characterization of Ag underpotential deposition on gold. The results indicate mass deposition of 412.2 ng for the WE and 345.6 ng for the CE, reflecting a difference of the initially-present Ag adhered to the surface. We also performed higher harmonic measurements that further corroborate the sensitivity and reproducibility of the dual EC-QCM. The demonstrated approach is especially intriguing for electrochemical energy storage applications where mass detection with multiple electrodes is desired.

This paper reports the development of a new composite material as a matching medium for medical microwave diagnostic systems, where maximizing the microwave energy that penetrates the interrogated tissue is critical for improving the quality of the diagnostic images. The proposed material has several advantages over what is commonly used in microwave diagnostic systems: it is semi-flexible and rigid, and it can maximize microwave energy coupling by matching the tissue’s dielectric constant without introducing high loss. The developed matching medium is a mirocomposite of barium titanate filler in polydimethylsiloxane (PDMS) in different weight-based mixing ratios. Dielectric properties of the material are measured using a Keysight open-ended coaxial slim probe from 0.5 to 10 GHz. To avoid systematic errors, a full dielectric properties calibration is performed before measurements of sample materials. Furthermore, the repeatability of the measurements and the homogeneity of the sample of interest are considered. Finally, to evaluate the proposed matching medium, its impact on a printed monopole antenna is studied. We demonstrate that the permittivity of the investigated mixtures can be increased in a controlled manner to reach values that have been previously shown to be optimal for medical microwave imaging (MWI) such as stroke and breast cancer diagnostic applications. As a result, the material is a good candidate for supporting antenna arrays designed for portable MWI scanners in applications such as stroke detection.

Lithium-ion batteries (LIBs) are currently the most relevant energy storage solution for a wide field of applications starting from mobile communication and going to high power applications in electric vehicles. To assess the quality of a LIB either during production or in post-production, its self- discharge rate is an important parameter. Here we present a new method for precise potentiostatic self-discharge measurements (SDMs) that is very sensitive and considerably faster than other currently available methods. We validated the new SDM by measuring ten commercial 3000 mAh 21700 LIBs resulting in roughly 3 μA self-discharge current with a noise level of 0.1 μA, at 60% state of charge (SoC). Higher self- discharge currents of about 40 μA were observed at a higher SoC of 80%. To model the SDM, the electrochemical processes are coupled with a 3D temperature FEM and an electric circuit model of the cell self-discharge, resulting in a good overlap and a quantitative value of the LIB self-discharge resistance. Furthermore, we tested a realistic physical self-discharge scenario of the formation of Lithium dendrites by comparing experimental and modelled self-discharge resistance values.

The dielectric properties of biological tissues are fundamental for the design of electromagnetic medical devices as well as in non-ionizing radiation dosimetry studies. In recent studies, dielectric data has been typically collected using the openended coaxial probe and the vector network analyzer (VNA) setup. In this work, we replace the traditional swept frequency VNA from this setup with a more compact microwave transceiver. The microwave transceiver uses a novel broadband, multi-tone source and broadband receivers to capture the instantaneous Sparameters at multiple tones simultaneously. We conducted dielectric properties measurements on standard liquids which have known dielectric properties using our modified setup and compared the results with the theoretical values. We also conducted the same measurements with the typical setup which includes the swept frequency VNA and compared the performances of the two measurement setups. We concluded that the microwave transceiver can provide faster measurement speeds than the conventional VNA without sacrificing measurement precision and accuracy.

Nanoscale investigations by scanning probe microscopy have provided major contributions to the rapid development of organic-inorganic halide perovskites (OIHP) as optoelectronic devices. Further improvement of device level properties requires a deeper understanding of the performance-limiting mechanisms such as ion migration, phase segregation, and their effects on charge extraction both at the nano- and macroscale. Here, we have studied the dynamic electrical response of Cs0.05(FA0.83MA0.17)0.95PbI3-xBrx perovskite structures by employing conventional and microsecond time-resolved open-loop Kelvin probe force microscopy (KPFM). Our results indicate strong negative charge carrier trapping upon illumination and very slow (>1 s) relaxation of charges at the grain boundaries. The fast electronic recombination and transport dynamics on the microsecond scale probed by time-resolved open-loop KPFM show diffusion of charge carriers toward grain boundaries and indicate locally higher recombination rates because of intrinsic compositional heterogeneity. The nanoscale electrostatic effects revealed are summarized in a collective model for mixed-halide CsFAMA. Results on multilayer solar cell structures draw direct relations between nanoscale ionic transport, charge accumulation, recombination properties, and the final device performance. Our findings extend the current understanding of complex charge carrier dynamics in stable multication OIHP structures.

A systematic and quantitative comparison of electrical detection systems in scanning microwave microscopy is reported. Scanning microwave microscopy (SMM) is capable of investigating nanoscale electrical properties with high accuracy over a broad frequency range of 1–20 GHz. However, due to the passive matching network only discrete frequencies can be used every 1 GHz with varying signal-to-noise ratio (SNR). Here we study in detail the impedance matching mechanism using an interferometric network where a two-port measurement is implemented with a reduction of the trace noise due to signal subtraction. The interferometer setup shows superior performance resulting in a 2–8 fold increased SNR with respect to the standard shunt solution, in addition to stable broadband performance over the full frequency range. We perform a comparison of the electrical sensitivity obtained using a direct connection from the network analyser to probe, the typically implemented shunt-resonator impedance matching network, and the proposed interferometer setup. The interferometer SMM allows us also for calibrated impedance measurements, which we demonstrate on Tobacco mosaic viruses with 18-nm diameter, with a capacitance resolution of 0.67 attoFarads at 10 ms acquisition time per pixel.

A new calibration method for nanoscale complex impedance imaging with the scanning microwave microscope is presented, which allows to calibrate the complete frequency range in a short automated procedure. The vector network analyzer and the corresponding electronically switched calibration capabilities in combination with time domain gating and microwave network modeling are used to de-embed the full system. The entire calibration requires not more than 5 min and the acquisition of one single electrostatic force microscopy approach curve. In order to demonstrate the broadband capabilities, calibrated approach curves at various frequencies are presented. Nano-Schottky diodes on a semiconductor substrate as well as biological cells were measured to demonstrate that the sample conductance and susceptance are in agreement with the theoretical expectations for the samples. This advanced workflow of quantitative impedance calibration may have many applications in the fields of semiconductor failure analysis, 2-D materials, and biological samples in their native liquid environment.

We quantitatively image the doping concentration and the capacitance of a high-voltage lateral metal-oxide-semiconductor transistor device with a channel length of 0.5 μm at 20-GHz frequency using scanning microwave microscopy (SMM). The transistor is embedded in a deep n-well forming a flat pn-junction with the p-substrate, with the shape of the pn-junction resolved in the SMM images. Calibrated dC/dV imaging of the device revealed doping concentration values in the range of 1015–1019 atoms/cm 3, including the p-body, n-drift region, n-source-diffusion, as well as all the pn-junctions and the silicon/oxide interfaces at a minimum feature size of 350 nm and SMM electrical resolution of 60 nm. SMM doping concentrations have been compared with technology computer-aided design simulations, resulting in a quantitative agreement between model and experiment. dC/dV images have been acquired at different tip dc bias voltages, allowing to determine the p and n dopant polarity. From the reflection scattering S11 signal calibrated capacitance measurements have been obtained from the various transistor regions in the range of 300 aF to 1 fF. The results suggest that both dC/dV dopant profiling and capacitance measurements can be used for quantitative nanoscale semiconductor device imaging.

Multitude of antennas are typically used in microwave imaging systems. Here we outline a simple and effective calibration method for multiport imaging systems. By using only one additional component, an electronic calibration module (ECal), one port is calibrated and the calibration plane is thereby moved to the antenna connector. Assuming all antennas interact with the test phantom in the same way, the one-port calibration is transferred to all other antennas. For full calibration including the transmission path between antennas, the unknown thru technique is used. This calibration procedure is simple and it can be fully automated, and no RF components are perturbed., Comment: Funding by H2020 GA No. 764479 (Emerald) and GA No. 761036 (MMAMA)

We investigate the nearfield dipole mobility of protein membranes in a wide frequency range from 3 kHz to 10 GHz. The results of our nanoscale dielectric images and spectra of bacteriorhodopsin (bR) reveal Debye relaxations with time constants of τ ∼ 2 ns and τ ∼ 100 ns being characteristic of the dipole moments of the bR retinal and α-helices, respectively. However, the dipole mobility and therefore the protein biophysical function depend critically on the amount of surface water surrounding the protein, and the characteristic mobility in the secondary structure is only observed for humidity levels

The paper presents a methodology for de-embedding scanning microwave microscopy (SMM) measurements, mainly for semiconductor characterization. Analytical modeling, a parametric study and experimental verification are presented. The proposed methodology is based on the analysis of system response in the linear scale, instead of the dB scale commonly utilized in RF measurements, and on expressing the standard calibration capacitances per unit area. In this way the total measured capacitance is determined by the tip area which is then obtained as a result of the model fitting on the experimental data. Additional evaluation is performed by a straightforward experimental comparison with the usually adopted technique that is based on the electrostatic force microscopy approach curve method. The results obtained by the application of both techniques on the same tip during the same experiment were found to be in good agreement and moreover allowed a detailed discussion on the features of each one of the two methodologies. The paper provides also in this way useful knowledge for the potential users in order to choose the most appropriate technique according to the corresponding SMM application. Display Omitted A methodology for de-embedding scanning microwave microscopy measurements is presented.The proposed analysis is based on the assessment of the SMM system response in the linear scale.The methodology is experimentally evaluated by a straightforward comparison with an EFM based calibration method.Based on the obtained results the features of each methodology are also discussed in details.The paper provides a full picture of the up to date available experimental techniques for de-embedding SMM measurements.

We quantified the electric permittivity of single bacterial cells at microwave frequencies and nanoscale spatial resolution by means of near-field scanning microwave microscopy. To this end, calibrated complex admittance images have been obtained at ∼19 GHz and analyzed with a methodology that removes the nonlocal topographic cross-talk contributions and thus provides quantifiable intrinsic dielectric images of the bacterial cells. Results for single Escherichia coli cells provide a relative electric permittivity of ∼4 in dry conditions and ∼20 in humid conditions, with no significant loss contributions. Present findings, together with the ability of microwaves to penetrate the cell membrane, open an important avenue in the microwave label-free imaging of single cells with nanoscale spatial resolution.

Recent developments in Scanning Microwave Microscopy for investigation of 2D materials and buried dopant structures are shown. Additionally, a new methodology termed wideband Electrostatic Force Microscopy will be presented that allows for investigation of frequency dependent electrical properties in a range from kHz to GHz.

Presentation of the MMAMA project and its objectives during an EMCC workshop in Brussels, on 11 June 2018. The presentation displayed, giving some wide inputs on the project.

International audience; A calibration algorithm based on one-port vector network analyzer (VNA) calibration for scanning microwave microscopes (SMMs) is presented and used to extract quantitative carrier densities from a semiconducting n-doped GaAs multilayer sample. This robust and versatile algorithm is instrument and frequency independent, as we demonstrate by analyzing experimental data from two different, cantilever- and tuning fork-based, microscope setups operating in a wide frequency range up to 27.5 GHz. To benchmark the SMM results, comparison with secondary ion mass spectrometry is undertaken. Furthermore, we show SMM data on a GaAs p-n junction distinguishing p- and n-doped layers.

In this paper, the basic principles of Near-Field Microscopy will be reviewed with focus on the micro- and nano-scale resolution configurations for material science measurements. Results on doping profile, dielectric and magnetic properties will be presented, with details on the calibration protocols needed for quantitative estimation of the dielectric constant and of the permeability.

One-port reflection calibration is a widely used technique for RF and microwave VNA measurements in a broad range of applications including on-wafer chip testing, production testing, and microwave imaging. Recent developments in the field of antenna tuning components lead to advanced, highly stable MEMS-based variable capacitors. In this study we present the use of an antenna tuning integrated circuit (IC) for realizing a compact and fast transfer standard for one-port calibration. In contrast to traditional Short-Open-Load methods a new workflow that uses different capacitance states was developed. Together with least-squared-error solving this leads to improved calibration performance. Verification against metrology grade standards showed agreement of less than −45 dB vector difference. In addition, an estimation of the expected S-parameter error due to temperature deviations was performed. The new calibration workflow can be used in applications where multiple ports need to be calibrated fast and accurate.

Nanoparticle labels have enhanced the performance of diagnostic, screening, and other measurement applications and hold further promise for more sensitive, precise, and cost-effective assay technologies. Nevertheless, a clear view of the biomolecular interactions on the molecular level is missing. Controlling the ratio of molecular recognition over undesired nonspecific adhesion is the key to improve biosensing with nanoparticles. To improve this ratio with an aim to disallow nonspecific binding, a more detailed perspective into the kinetic differences between the cases is needed. We present the application of two novel methods to determine complex binding kinetics of bioconjugate nanoparticles, interferometry, and force spectroscopy. Force spectroscopy is an atomic force microscopy technique and optical interferometry is a direct method to monitor reaction kinetics in second-hour timescale, both having steadily increasing importance in nanomedicine. The combination is perfectly suited for this purpose, due to the high sensitivity to detect binding events and the ability to investigate biological samples under physiological conditions. We have attached a single biofunctionalized nanoparticle to the outer tip apex and studied the binding behavior of the nanoparticle in a sandwich-type immunoassay using dynamic force spectroscopy in millisecond timescale. Utilization of the two novel methods allowed characterization of binding kinetics in a time range spanning from 50 ms to 4 h. These experiments allowed detection and demonstration of differences between specific and nonspecific binding. Most importantly, nonspecific binding of a nanoparticle was reduced at contact times below 100 ms with the solid-phase surface.

Microwave microscopy enables three-dimensional characterization of atomically thin semiconductor structures with nanometer precision., It is now possible to create atomically thin regions of dopant atoms in silicon patterned with lateral dimensions ranging from the atomic scale (angstroms) to micrometers. These structures are building blocks of quantum devices for physics research and they are likely also to serve as key components of devices for next-generation classical and quantum information processing. Until now, the characteristics of buried dopant nanostructures could only be inferred from destructive techniques and/or the performance of the final electronic device; this severely limits engineering and manufacture of real-world devices based on atomic-scale lithography. Here, we use scanning microwave microscopy (SMM) to image and electronically characterize three-dimensional phosphorus nanostructures fabricated via scanning tunneling microscope–based lithography. The SMM measurements, which are completely nondestructive and sensitive to as few as 1900 to 4200 densely packed P atoms 4 to 15 nm below a silicon surface, yield electrical and geometric properties in agreement with those obtained from electrical transport and secondary ion mass spectroscopy for unpatterned phosphorus δ layers containing ~1013 P atoms. The imaging resolution was 37 ± 1 nm in lateral and 4 ± 1 nm in vertical directions, both values depending on SMM tip size and depth of dopant layers. In addition, finite element modeling indicates that resolution can be substantially improved using further optimized tips and microwave gradient detection. Our results on three-dimensional dopant structures reveal reduced carrier mobility for shallow dopant layers and suggest that SMM could aid the development of fabrication processes for surface code quantum computers.

We present a new calibration method for nanoscale complex impedance imaging by scanning microwave microscope (SMM), which does not require any calibration samples. Instead, the vector network analyser (VNA) and the corresponding electronically switched calibration (ECal) capabilities in combination with time domain gating and microwave network modelling are used to de-embed the full system. Based on this workflow the measured complex SMM-S11 signal can be directly split into the reactive and lossy sample behavior. Nano Schottky diodes on a semiconductor substrate were measured to demonstrate that the sample conductance and susceptance correspond directly to S11 amplitude and phase, respectively. In the final step of the workflow we apply a calibration based on SMM tip approach curves resulting in quantitative impedance values. This method can have various applications starting from semiconductor failure analysis to novel 2D materials and biological cells in liquid environment.

The application of scanning microwave microscopy (SMM) to extract calibrated electrical properties of cells and bacteria in air is presented. From the S 11 images, after calibration, complex impedance and admittance images of Chinese hamster ovary cells and E. coli bacteria deposited on a silicon substrate have been obtained. The broadband capabilities of SMM have been used to characterize the bio-samples between 2 GHz and 20 GHz. The resulting calibrated cell and bacteria admittance at 19 GHz were Y cell = 185 μS + j285 μS and Y bacteria = 3 μS + j20 μS, respectively. A combined circuitry-3D finite element method EMPro model has been developed and used to investigate the frequency response of the complex impedance and admittance of the SMM setup. Based on a proposed parallel resistance-capacitance model, the equivalent conductance and parallel capacitance of the cells and bacteria were obtained from the SMM images. The influence of humidity and frequency on the cell conductance was experimentally studied. To compare the cell conductance with bulk water properties, we measured the imaginary part of the bulk water loss with a dielectric probe kit in the same frequency range resulting in a high level of agreement.

session poster; International audience; The paper presents an experimental study aiming to highlight the potential of scanning microwave microscopy (SMM) as a non-destructive high precision characterization tool for SOI technology. Two identical SOI wafers having passivated and non-passivated top Si film surfaces have been assessed. Differential microwave measurements were found capable of detecting differences in the structures of the two samples. The results support the conclusion that, after appropriate calibration method, SMM may provide a powerful tool offering nm scale characterization for SOI technology.

We developed an impedance quartz crystal microbalance (QCM) approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 Ω were measured with corresponding dissipation values of 0.01 µU (micro dissipation units). The broadband impedance capabilities allow measurements between 20 Hz and 120 MHz including higher harmonic modes of up to 11th order for a 10 MHz fundamental resonance frequency quartz crystal. We demonstrate the adsorbed mass, calibrated resistance, and quantitative dissipation measurements on two biological systems including the high affinity based avidin-biotin interaction and nano-assemblies of polyelectrolyte layers. The binding affinity of a protein-antibody interaction was determined. The impedance QCM is a versatile and simple method for accurate and calibrated resistance and dissipation measurements with broadband measurement capabilities for higher harmonics measurements.

In this paper, we present in detail the design, both electromagnetic and mechanical, the fabrication, and the test of the first prototype of a Scanning Microwave Microscope (SMM) suitable for a two-port transmission measurement, recording, and processing the high frequency transmission scattering parameter S21 passing through the investigated sample. The S21 toolbox is composed by a microwave emitter, placed below the sample, which excites an electromagnetic wave passing through the sample under test, and is collected by the cantilever used as the detector, electrically matched for high frequency measurements. This prototype enhances the actual capability of the instrument for a sub-surface imaging at the nanoscale. Moreover, it allows the study of the electromagnetic properties of the material under test obtained through the measurement of the reflection (S11) and transmission (S21) parameters at the same time. The SMM operates between 1 GHz and 20 GHz, current limit for the microwave matching of the cantilever, and the high frequency signal is recorded by means of a two-port Vector Network Analyzer, using both contact and no-contact modes of operation, the latter, especially minded for a fully nondestructive and topography-free characterization. This tool is an upgrade of the already established setup for the reflection mode S11 measurement. Actually, the proposed setup is able to give richer information in terms of scattering parameters, including amplitude and phase measurements, by means of the two-port arrangement.

In this work, microwave characterization of magnetic materials using the scanning microwave microscopy (SMM) technique is presented. The capabilities of the SMM are employed for analyzing and imaging local magnetic properties of the materials under test at the nanoscale. The analyses are performed by acquiring both amplitude and phase of the reflected microwave signal. The changes in the reflection coefficient S-11 are related to the local properties of the material under investigation, and the changes in its magnetic properties have been studied as a function of an external DC magnetic bias. Yttrium iron garnet (YIG) films deposited by RF sputtering and grown by liquid phase epitaxial (LPE) on gadolinium gallium garnet (GGG) substrates and permalloy samples have been characterized. An equivalent electromagnetic transmission line model is discussed for the quantitative analysis of the local magnetic properties. We also observed the hysteretic behavior of the reflection coefficient S11 with an external bias field. The imaging and spectroscopy analysis on the experimental results are evidently indicating the possibilities of measuring local changes in the intrinsic magnetic properties on the surface of the material. (C) 2016 Elsevier B.V. All rights reserved.

We demonstrate simultaneous transverse dynamic force microscopy and molecular recognition imaging using tuning forks as piezoelectric sensors. Tapered aluminum-coated glass fibers were chemically functionalized with biotin and anti-lysozyme molecules and attached to one of the prongs of a 32 kHz tuning fork. The lateral oscillation amplitude of the tuning fork was used as feedback signal for topographical imaging of avidin aggregates and lysozyme molecules on mica substrate. The phase difference between the excitation and detection signals of the tuning fork provided molecular recognition between avidin/biotin or lysozyme/anti-lysozyme. Aggregates of avidin and lysozyme molecules appeared as features with heights of 1–4 nm in the topographic images, consistent with single molecule atomic force microscopy imaging. Recognition events between avidin/biotin or lysozyme/anti-lysozyme were detected in the phase image at high signal-to-noise ratio with phase shifts of 1–2°. Because tapered glass fibers and shear-force microscopy based on tuning forks are commonly used for near-field scanning optical microscopy (NSOM), these results open the door to the exciting possibility of combining optical, topographic and biochemical recognition at the nanometer scale in a single measurement and in liquid conditions.

Higher harmonic contributions in the movement of an oscillating atomic force microscopy (AFM) cantilever are generated by nonlinear tip-sample interactions, yielding additional information on structure and physical properties such as sample stiffness. Higher harmonic amplitudes are strongly enhanced in liquid compared to the operation in air, and were previously reported to result in better structural resolution in highly organized lattices of proteins in bacterial S-layers and viral capsids [J. Preiner, J. Tang, V. Pastushenko, P. Hinterdorfer, Phys. Rev. Lett. 99 (2007) 046102]. We compared first and second harmonics AFM imaging of live and fixed human lung epithelial cells, and microvascular endothelial cells from mouse myocardium (MyEnd). Phase-distance cycles revealed that the second harmonic phase is 8 times more sensitive than the first harmonic phase with respect to variations in the distance between cantilever and sample surface. Frequency spectra were acquired at different positions on living and fixed cells with second harmonic amplitude values correlating with the sample stiffness. We conclude that variations in sample stiffness and corresponding changes in the cantilever-sample distance, latter effect caused by the finite feedback response, result in second harmonic images with improved contrast and information that is not attainable in the fundamental frequency of an oscillating cantilever.

Atomic force microscopy (AFM) was used to study the effects of bleaching on the morphology of the enamel surface with nanoscale resolution. Samples of human tooth enamel with native (pumiced) or fine-polished surfaces were examined before and after bleaching with 30% carbamide peroxide. The obtained profilometric AFM data revealed significant morphological surface alterations. After 1 h of bleaching, the surface roughness increased significantly from 19 +/- 4nm to 33 +/- 5 nm. Six-hour bleaching did not produce any significant further increase in enamel surface roughness. The interrod junction depth raised more than twice after 1 h of bleaching. After 6 h of bleaching, a further and significant increase in interrod junction depth was recorded. This alteration might be a consequence of oxidation and a subsequent partial lysis of the tooth enamel matrix proteins.

Minor group human rhinoviruses (HRVs) attach to members of the low-density lipoprotein receptor family and are internalized via receptor-mediated endocytosis. The attachment of HRV2 to the cell surface, the first step in infection, was characterized at the single-molecule level by atomic force spectroscopy. Sequential binding of multiple receptors was evident from recordings of characteristic quantized force spectra, which suggests that multiple receptors bound to the virus in a timely manner. Unbinding forces required to detach the virus from the cell membrane increased within a time frame of several hundred milliseconds. The number of receptors involved in virus binding was determined, and estimates for on-rate, off-rate, and equilibrium binding constant of the interaction between HRV2 and plasma membrane-anchored receptors were obtained.

Piezoelektrische Materialien sind ein zentrales Element der Rastersondenmikroskopie. Dieser Artikel gibt einen Uberblick uber die dominanten Effekte, welche bei Piezos bei der Verwendung als Aktor bzw. Sensor auftreten. Dabei wird auf die Hysterese von Piezos eingangen und ein Verfahren vorgestellt, wie diese zum Teil kompensiert werden kann. Weiters wird das dynamische Verhalten von Piezoelementen untersucht und gezeigt, wie mechanische Resonanzen durch sie angeregt werden und wie diese auch minimiert werden konnen. Quarzoszillatoren konnen auch als Sensoren in der Rastersondenmikroskopie verwendet werden. Eine konkrete Ausfuhrung ist in Form einer Stimmgabel. Fur diese werden ein elektrisches Modell mit einem mechanischen in Zusammenhang gebracht und beide durch Messungen bestatigt.