Force Curve Measurements Research Articles

The interface between ice and alcohols analyzed by atomic force microscopy.

This study investigates the interface between ice and organic solvents using atomic force microscopy (AFM). Atomically flat ice surfaces were prepared and observed by AFM in 1-octanol, 1-hexanol, and 1-butanol. The results show differences in surface roughness influenced by the interaction of ice and alcohols. Young's modulus of ice was analyzed by force curve measurements, providing valuable insights into the properties of ice in liquid environments. The results showed the characteristics of the ice surface in different solvents, suggesting potential applications in understanding surface and interface phenomena associated with ice under realistic conditions.

Maximum in-vivo joint contact forces double during active compared to assisted motion in the glenohumeral joint and decline long-term due to rotator cuff pathologies.

Rehabilitation programs advocate early passive and assisted motion after rotator cuff repair to induce healing und maintaining range of motion while avoiding excessive strain on the repaired tendons. In-vivo glenohumeral joint contact forces reflect the compressive forces generated by the rotator muscles. In the present study, maximum in-vivo joint contact forces (FresMax) were determined to compare active and assisted execution of a single movement and the long-term development of joint compression forces. FresMax were measured in six patients who received instrumented, telemetric modified anatomical hemi endoprostheses of the shoulder joint between 2006 and 2008. Data were gathered 23months postoperatively (2006-2010), were analysed and compared with measurements 133months postoperatively. Additional imaging was obtained as x-rays and ultrasound examination. Data analysis was conducted by synchronizing video tapes and measured force curves. New imaging showed a rupture of the M. supraspinatus and progressive joint degeneration. FresMax nearly doubled during active compared to assisted execution of each of the four chosen movements. Over the course of 133months post-surgery, the studied movements showed a decrease of active compression force, probably due to a ruptured supraspinatus, resulting in a lower active/assisted ratio. A long term follow up after eleven years, eight out of ten measured movements showed a decrease of FresMax. These results support current rehabilitation protocols recommending early passive and assisted motion to limit activation of the rotator muscles generating compressive forces. Following degeneration of the rotator cuff, active joint contact forces decrease over time.Level of evidence: III.

Arrangement of Al Ions between Ionic Liquid and Graphite Electrode Interface by AFM Force Curve Measurement

Arrangement of Al Ions between Ionic Liquid and Graphite Electrode Interface by AFM Force Curve Measurement

Optimizing the methodology for accurate and accessible slip length measurement with atomic force microscopy

The remarkable performance of cooling devices employing nano- and microscale channels has drawn considerable interest, highlighting the need for surfaces with large slip lengths to improve their efficiency. However, the large errors in slip length associated with existing techniques hinder a clear understanding of slip phenomena. In this paper, we evaluate existing analytical methods for slip length measurement with atomic force microscopy (AFM) and propose a new reliable method. We performed force curve measurements on mica, silica and highly ordered pyrolytic graphite surfaces in water using an AFM equipped with a colloidal probe. The obtained force curves were analyzed through three methods: two commonly utilized procedures, namely the recursive and intercept methods, and a novel one called the two-parameter method which we developed. Our analyses showed that the recursive method yielded slip lengths with relatively large errors, fluctuation of ±5.8 nm, which were due to inaccuracies in the cantilever's spring constant and the fluid viscosity. On the other hand, it was found that the intercept method leads to restrictions on the choice of fitting range because of the simplified formula for viscous drag. As a result, by altering the data range, the calculated slip length shows significant variations within the ranges of ±27.5 nm. The two-parameter method, unlike the standard ones, overcome these drawbacks. This method requires no pre-measured parameters, and the slip length fluctuation is independent of the fitting range and only ±3.6 nm, which is around 2/3 of that observed in the recursive method and 1/8 of that in the intercept method. Our study optimizes existing analytical protocols and offers a new way for accessible and reliable calculations of slip lengths.

In situ thermal noise measurements under nanoindentation of suspended graphene

We demonstrated thermal noise measurement under the nanoindentation of monolayer and bilayer graphene nanodrums. The resonant oscillation of the cantilever excited only by a thermal energy is detectable even in the case of contact with a suspended graphene. The contact resonance fRequency can be obtained in 1 millisecond intervals during the force curve measurement by optimizing the parameters of a real-time spectrum analyzer. The pretension value of the graphene nanodrum is evaluated by the minimum frequency just when the applied force of the cantilever becomes zero. The simultaneous measurement of the force and the resonant frequency with respect to the deformation of the graphene nanodrum enables us to determine the value of InvOLS (inverse optical lever sensitivity) more accurately in each measurement. From the analysis scheme, force curve measurements of the graphene nanodrums with the same diameters show good reproducibility. We also revealed that the effective spring constant of the graphene nanodrums consists of a weak sample-dependent pretension factor and a deformation-dependent factor proportional to the number of graphene layers.

TiO2 Passivated Zno Nanoarray Layer Based Fluoroalkylsilane Film for Photovoltaic Optical Glass: Achieving UV Shielding, Acid Rain Resistance, and Self‐Cleaning Properties

AbstractPhotovoltaic technology is a prominent source of renewable energy, but maintenance costs and efficiency attenuation of large photovoltaic devices are significant issues due to their vast energy conversion area. To reduce costs and facilitate maintenance, superhydrophobic surfaces with self‐cleaning properties have been developed for photovoltaic glass. In this study, transparent ZnO nanoarrays (NAs) are synthesized on photovoltaic glass, with Eu3+ doping enhancing the ultraviolet radiation resistance of photovoltaic devices and slightly increasing visible transmittance. A TiO2 passivation layer is introduced on the ZnO NAs surface to enhance acid resistance and mitigate corrosion caused by acidic rainwater. Fluoroalkylsilane (POTS) modification achieves superhydrophobicity with a water contact angle of 160.25°, as demonstrated by droplet rolling experiments. Micro‐interaction of superhydrophobic properties is further investigated by force curve measurement using atomic force microscope, showing almost no nanometer water moisture on the superhydrophobic surface, but conspicuous water moisture on the control glass surface. Finally, simulated models and practical silicon crystal solar cells fabricated using the self‐cleaning glass show excellent acid rain resistance, self‐cleaning, and long service life properties, with no power conversion efficiency degeneration during a 40‐day outdoor application test.

Pilot study: validity and reliability of textile insoles used to measure the characteristics of landing tasks during rehabilitation and artistic gymnastics

ObjectivesArtistic gymnastics is a sport where most athletes start at an early age and training volumes are high. Hence, overuse and acute injuries are frequent due to the load endured during landing tasks. During landing, the ground reaction force (GRF) is up to 15.8 times the body weight and therefore reliable GRF measurements are crucial. The gold standard for GRF measurements are force plates. As force plates are mostly used in a constrained laboratory environment, it is difficult to measure the GRF in representative training settings. Textile insoles (novel GmbH, Munich, Germany) exist, which can be used to measure dynamic GRF. Hence, the motivation of this study is to test the validity and reliability of these insoles during landing tasks. GRF was measured during four different exercises, in two test subjects and compared to concurrent force plate data.ResultsTwelve out of 16 statistical parametric mapping plots showed no significant difference between the measured force curves of insoles and force plates. Across conditions, the root mean square error of the maximal vertical GRF was 21 N/kg and an impulse 0.4 Ns/kg. The intraclass correlation coefficient (ICC 2,1) ranged from 0.02 to 0.76 for maximal vertical GRF and from − 0.34 to 0.76 for impulse. The insoles are a valid measurement tool for GRF curve progression and impulse during landing but underestimate the maximal vertical GRF.

Fructus cannabis protein extract powder as a green and high effective corrosion inhibitor for Q235 carbon steel in 1 M HCl solution

The Fructus cannabis protein extract powder (FP), was firstly used as a green and high effective corrosion inhibitor through a simple water-extraction method. The composition and surface property of FP were characterized by FTIR, LC/MS, UV, XPS, water contact angle and AFM force-curve measurements. Results indicate that FP contains multiply functional groups, such as NH, CO, CN, CO, etc. The adsorption of FP on the carbon steel surface makes it higher hydrophobicity and adhesion force. The corrosion inhibition performance of FP was researched by electrochemical impedance, polarization curve and differential capacitance curve. Moreover, the inhibitive stability of FP, and the effects of temperature and chloride ion on its inhibition property were also investigated. The above results indicate that the FP exhibits excellent corrosion inhibition efficiency (~98 %), and possesses certain long-term inhibitive stability with inhibition efficiency higher than 90 % after 240 h immersion in 1 M HCl solution. The high temperature brings about the FP desorption on the carbon steel surface, while high concentration of chloride ion facilitates the FP adsorption. The adsorption mechanism of FP follows the Langmuir isotherm adsorption. This work will provide an insight for protein as a green corrosion inhibitor.

Inner and Interfacial Environmental Nanoarchitectonics of Supramolecular Assemblies Formed by Amphiphiles: from Emergence to Application.

The inner and interfacial environments of self-assemblies provide fascinating nano-space for selective and efficient chemical reactions and processes. In biological systems, various chemical reactions, molecular recognition, and transport occur precisely and selectively by virtue of effective molecular interactions on biological membranes and proteins. Considering these advantages and the concept of nanoarchitectonics, we demonstrated that the photochromism of a lophine dimer was accelerated by using confined nano-spaces formed by surfactant micelles. The photoresponsive micelles were used for the rapid controlled release of a model drug upon ultraviolet light irradiation. Furthermore, selective ion recognition inside the self-assembled molecular films at the interfaces was investigated. The anion-π interaction between the anion and an electron-deficient aromatic ring was evaluated on a solid substrate modified with a naphthalenediimide (NDI) analog. Force curve measurements afforded a quantitative analysis of anion-π interactions on the NDI film. The strength of anion-π interactions is regulated by the electric fields on the electrode. An optical probe was developed to visualize the distribution of Cs ions in the soil, plant bodies, and aqueous media using an optode system. Advances in the development of molecular functional systems are expected based not only on molecular structures but also on the spaces and environments produced by them.

Intentionally created localized bridges for electron transport through graphene monolayer between two metals

Monolayer graphene (1LG) is frequently unpredictably modified by supporting material so that it limits development of devices. Van der Waals interaction is dominant in the models describing the in-plane processes, including the electrical charge transport. However, the current flow perpendicular to the plane of the graphene is still less understood. This report analysed specific aspect of the perpendicular current and disclosed an original way to create transport bridges perpendicular to the plane across the 1LG. The most extraordinary finding is that the electron transport between two parallel metal surfaces can be shut down and opened if the metals are separated by the 1LG. The electron transmission can be intentionally varied in this metal–1LG–metal (M–G–M) system by pressure. In the experimental study the AFM force curve and tunnelling current measurements were combined when the external load force (0–1200 nN) and electrical potential (−1.5 V to +1.5 V) were used. It is proved that for low voltages (<±9 mV) a bridge is opened perpendicular to the graphene across the M–G–M systems by the external force, if the compression dependent Fermi level crosses electronic states in the interfaces and graphene. The localised bridges with diameter about 10–40 nm can be opened and kept continuously by the stabilised force in separated points of the system. However, the predictable changes can be produced in the system if the voltage and the force exceeded critical magnitudes. A combined model was proposed acceptable to explain the bridging and predictably modify the characteristics.

Determining Amplitudes of Standing Surface Acoustic Waves via Atomic Force Microscopy

Atomic force microscopy is a tool for characterizing surface acoustic waves, in particular for high frequencies, where the wavelength is too short to be resolved by laser interferometry. A caveat is, that the cantilever deflection is not equal to the amplitude of the surface acoustic wave. We show that the energy transfer from the moving surface to the cantilever instead leads to a deflection exceeding the surface modulation. We present a method for an accurate determination of surface acoustic wave amplitudes based on comparing force-curve measurements with the equation of motion of a driven cantilever. We demonstrate our method for a standing surface acoustic wave on a $\mathrm{Ga}\mathrm{As}$ crystal confined in a focusing cavity with a resonance frequency near 3 GHz.

Development of a force measurement system with a large punctual measurement range

Atomic force microscopes (AFMs) are precise force measurement instruments that can be used to measure multiple surface properties, such as adhesion force, surface potential, and elasticity at the nanoscale. AFM is increasingly used in diverse fields, especially in industrial applications. However, most existing commercial AFMs provide a scanning range of less than a few 100 μm. Moreover, the size of the sample must usually be less than a few centimeters to fit the mechanical constraints of the device. In this paper, we propose a gantry-type force measurement system that can perform force curve measurements over a large range. The measurement range of the proposed device is 240 mm minus the sample width in air environments. In liquid environments, the measurement range is mainly limited by the size of the Petri dish. For instance, a measurement range of 41.5 mm can be achieved by using a Petri dish having a diameter of 85.5 mm. In the experiments, (a) surface adhesion measurements on the ultraviolet/ozone (UV/O3) treated glass slides in air and (b) surface potential measurements on a mica surface in water were performed. The experimental results were consistent with the values obtained by the commercial AFMs, which demonstrated the accuracy of the proposed system.

Red blood cell transport velocity in microchannels indicates the growth of abnormal subpopulation under oxidative stress

Background Transformation of red blood cells (RBCs, erythrocytes) during oxidative stress is a widespread phenomenon, which can be observed during natural aging of the cells, bank storage, under pathological conditions, and action of xenobiotics. Accumulated disturbances affect the deformability of RBCs, which slow down or even completely prevent their capillary passage. Here we investigated the transport of erythrocytes in microfluidic channels under the graduated oxidative stress. Material and Methods We used the extended towards low oxidant concentrations (0.1-1.5 mM) model of oxidative stress under the action of tert-butylperoxide (tBH), in vitro. In the developed microfluidic device with an array of 1.5x8x200 µm channels, we measured RBCs transit time by optical microscopy with further video analysis. This data was compared with flow cytometry, confocal microscopy, and AFM measurements to monitor abnormalities in erythrocytes under oxidative stress. Results The transit time measurements in the microfluidic device showed that under oxidative stress normal distribution of RBCs velocities became bimodal (Fig. 1). Increasing the concentration of tBh the number of cells with lower transit velocity increased. The flow cytometry and fluorescent microscopy showed that the oxidative stress led to the appearance of the group of cells with a smaller size (Fig. 2) and increased fluorescence of eosin-5-maleimide (EMA) that is caused by the clusterization of the transmembrane complex of band3. Moreover, the AFM force curve measurements indicated that the oxidative stress made the cells 2.9 times more rigid and stickier than the control ones. We assume that such changes directly influence the ability of RBCs to pass through microchannels. Conclusion Our data showed that the oxidative stress influences RBCs non uniformly, which leads to the division of all the cells into two subpopulations that differ in transit velocities in the microchannels, size, and membrane structure. The results show that erythrocytes velocity measurement in microfluidic devices is a promising technique for testing the degree of RBCs microrheological disorders during blood storage and aggressive drug therapy, including chemotherapy.

Pulsed laser activated impulse response encoder (PLAIRE): sensitive evaluation of surface cellular stiffness on zebrafish embryos.

Mechanical properties of cells and tissues closely link to their architectures and physiological functions. To obtain the mechanical information of submillimeter scale small biological objects, we recently focused on the object vibration responses when excited by a femtosecond laser-induced impulsive force. These responses are monitored by the motion of an AFM cantilever placed on top of a sample. In this paper, we examined the surface cellular stiffness of zebrafish embryos based on excited vibration forms in different cytoskeletal states. The vibration responses were more sensitive to their surface cellular stiffness in comparison to the Young's modulus obtained by a conventional AFM force curve measurement.

Evaluation of intercellular cross-linking abilities correlated with cytotoxicities of bispecific antibodies with domain rearrangements using AFM force-sensing

Bispecific antibodies (bsAbs) are a promising engineered antibody format; thus, technologies for the fabrication and evaluation of functional bsAbs are attracting increasing attention. Here, based on atomic force microscopy (AFM) force-sensing integrated with a metal cup-attached AFM chip (cup-chip) to ensure efficient capture of a target cell on a cantilever, we established a novel method for measuring cross-linking ability that is correlated with the cytotoxicities of bsAbs targeting two cells. We previously reported that domain rearrangements of bsAbs affected their cytotoxicities; however, no differences in cross-linking ability for soluble antigens were observed by surface plasmon resonance. We predicted that there would be differences in molecular configurations to avoid steric hindrance in the cross-linking of the two whole target cells. A picked-up T cell lymphoma cell on the cantilever using a cup-chip was moved to approach a cancer cell adhered to a dish, and force-curve measurements were performed. The resulting forces mediated by the cross-linking of bsAbs with different domain orders were well-correlated with their cytotoxicities. The AFM force-sensing method established herein may reflect steric hindrance of intercellular cross-linking, and thus has the potential to evaluate the net function of bsAbs and contribute to the generation of functional bsAbs.

Adsorption of Hydrophilic Amine-Based Protic Ionic Liquids on Iron-Based Substrates.

We synthesized hydrophilic amine-based protic ionic liquids (PILs) with hydroxy groups in their cations and anions, and characterized their adsorption at a solid (iron-based substrate) / aqueous solution interface. The IL samples employed in this study were triethanolamine lactate, diethanolamine lactate, and monoethanolamine lactate. Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements revealed that the adsorption mass of the hydrophilic PILs was larger than that of the comparative materials, including a non-IL sample (1,2,6-hexanetriol) and an OH-free sample in the cations (triethylamine lactate). Additionally, an increase in the number of hydroxy groups in the cations resulted in an increased adsorption mass. Force curve measurements by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) measurements proved the high adsorption density of the hydrophilic PILs on the iron-based substrate. A decreased kinetic friction coefficient was also observed in the hydrophilic PIL systems. Moreover, hydrophilic PILs are expected to have potential applications as water-soluble lubricants and additives for metal surface treatments.

Evaluating Solid-Electrolyte Interphases for Lithium and Lithium-free Anodes from Nanoindentation Features

Summary The morphology and mechanical property of SEIs for lithium anodes crucially affect the electrochemical cycling performance of Li-metal batteries such as Li-S and Li-O2 batteries. Herein, we establish the standards for rapidly assessing SEIs for Li and Li-free type of anodes by AFM nanoindentation features toward prediction of corresponding electrochemical performances. A series of single-layered and multi-layered SEIs with known composition and structures are purposely constructed. A set of unique nanoindentation features representative of mechanical properties of the basic SEIs are formed, serving as the standards for rapidly assessing the mechanical properties and electrochemical performances of unknown SEIs together with their Young’s modulus, smoothness, and thickness. To validate the applicability of the method, SEIs formed by electrochemical aging and formed on Cu substrates are further evaluated. Our work not only contributes to understanding the influence of SEIs on cycling performances but also provides a rapid way for screening SEIs.

Atomic Force Microscopy for Measuring Mechanical Properties of Cells in the Cortical Regions

Atomic force microscopy has become one of the most widely used tools in the mechanical characterization of cells to quantify elastic and viscoelastic properties. Here we briefly review AFM techniques, such as force curve, stress relaxation, creep, and force modulation measurements, developed for examining the mechanical properties of cells and describe how specific features of cellular samples are characterized.

Instrument-Dependent Factors Affecting the Precision in the Atomic Force Microscopy Stiffness Measurement of Nanoscale Liposomes.

The mechanical strength (stiffness) of liposomes affects their cellular uptake efficiency and drug release in drug delivery processes. We recently developed a tip shape evaluation method for improving the precision of liposome stiffness measurement by quantitative imaging (QI)-mode atomic force microscopy (AFM). The present study applied our method to the widely-used AFM instruments equipped for intermittent contact (IC)-mode force curve measurements, and examined instrument-dependent factors that affect the liposome stiffness measurements. We demonstrated that the evaluation of the tip shape for cantilever selection can be applicable to the IC mode as well as the QI mode. With the cantilever selection, the improved precision of the liposome stiffness was obtained when the stiffness of each liposome was determined from the slope in the force-deformation curve by the IC-mode force curve measurement. Further, the stiffness values were found to be similar to that measured by QI-mode measurements. These results indicate that our developed method can be widely used via IC-mode force curve measurements as well as via QI mode. It was also revealed that spatial drift of the cantilever position was instrument-dependent factors which could affect the precision of liposome stiffness measurements in the case of IC-mode force curve measurement. Therefore, in case of stiffness measurement by IC-mode force curve measurement, it is vital to obtain force-deformation curves immediately after imaging a liposome for the precise stiffness measurement of liposomes. These findings will promote the usage of the AFM stiffness measurement method for the characterization of lipid nanoparticle-based drug delivery systems.

Zwitterionic Polypeptides: Chemoenzymatic Synthesis and Loosening Function for Cellulose Crystals.

A polypeptide with a GlyHisGly repeating sequence containing zwitterionic structures that effectively interact with cellulose was synthesized for dissociation of cellulose crystals. Polypeptide with the GlyHisGly sequence was synthesized by chemoenzymatic polymerization and postfunctionalization of the His residues was performed to afford imidazolium butyrate on the side chains. The resulting zwitterionic polypeptide effectively dissociated bundles of tunicate cellulose nanocrystals, even when the conditions were mild and the concentration of the polypeptide was as low as 1-2 mg mL-1. Polypeptide treatment also affected the morphology of the cell walls in cultured plant cells, and the cellulose microfibril networks and amorphous polysaccharide layer were dissociated according to atomic force microscopy (AFM). The zwitterionic polypeptide treatment did not change the crystal structure of the cellulose nanocrystals. Analysis of the mechanical properties of the cellulose nanocrystals by force curve measurements using AFM revealed that the elastic modulus of the cellulose nanocrystals increased after treatment with the zwitterionic polypeptide, indicating that the amorphous part of the cellulose nanocrystals was removed by interactions with the polypeptide. At a concentration of the polypeptide that enabled the dissociation of the cellulose network, the zwitterionic polypeptide showed negligible cytotoxicity to the plant cells. The mild and noncytotoxic technique for loosening cellulose microfibrils/nanocrystals that was developed in this study has tremendous significance for the modification of cellulose in terms of polymer chemistry, material science, and plant biotechnology.