Simultaneous Force Measurements Research Articles

A Biophysics Toolbox for Reliable Data Acquisition and Processing in Integrated Force-Confocal Fluorescence Microscopy.

Integrated single-molecule force-fluorescence spectroscopy setups allow for simultaneous fluorescence imaging and mechanical force manipulation and measurements on individual molecules, providing comprehensive dynamic and spatiotemporal information. Dual-beam optical tweezers (OT) combined with a confocal scanning microscope form a force-fluorescence spectroscopy apparatus broadly used to investigate various biological processes, in particular, protein:DNA interactions. Such experiments typically involve imaging of fluorescently labeled proteins bound to DNA and force spectroscopy measurements of trapped individual DNA molecules. Here, we present a versatile state-of-the-art toolbox including the preparation of protein:DNA complex samples, design of a microfluidic flow cell incorporated with OT, automation of OT-confocal scanning measurements, and the development and implementation of a streamlined data analysis package for force and fluorescence spectroscopy data processing. Its components can be adapted to any commercialized or home-built dual-beam OT setup equipped with a confocal scanning microscope, which will facilitate single-molecule force-fluorescence spectroscopy studies on a large variety of biological systems.

Actuating droplets with electrowetting: Force and dynamics

AbstractElectrowetting on dielectric (EWOD) allows rapid movement of liquid droplets on a smooth surface, with applications ranging from lab‐on‐chip devices to micro‐actuators. The in‐plane force on a droplet is a key indicator of EWOD performance. This force has been extensively modeled but few direct experimental measurements are reported. We study the EWOD force on a droplet using two setups that allow, for the first time, the simultaneous measurement of force and contact angle, while imaging the droplet shape at 6000 frames/s. For several liquids and surfaces, we observe that the force saturates at a voltage of approximately 150 V. Application of voltages of up 2 kV, that is, 10 times higher than is typical, does not significantly increase forces beyond the saturation point. However, we observe that the transient dynamics, localized at the front contact line, do not show saturation with voltage. At the higher voltages, the initial front contact line speed continues to increase, the front contact angle temporarily becomes near zero, creating a thin liquid film, and capillary waves form at the liquid–air interface. When the localized EWOD forces at the contact line exceed the capillary forces, projectile droplets form. Increasing surface tension allows for higher droplet forces, which we demonstrate with mercury.

A Nonarray Soft Capacitive Tactile Sensor With Simultaneous Contact Force and Location Measurement for Intelligent Robotic Grippers

A Nonarray Soft Capacitive Tactile Sensor With Simultaneous Contact Force and Location Measurement for Intelligent Robotic Grippers

Differences in Mechanical, Electrical and Calcium Transient Performance of the Isolated Right Atrial and Ventricular Myocardium of Guinea Pigs at Different Preloads (Lengths)

There are only a few studies devoted to the comparative and simultaneous study of the mechanisms of the length-dependent regulation of atrial and ventricular contractility. Therefore, an isometric force-length protocol was applied to isolated guinea pig right atrial (RA) strips and ventricular (RV) trabeculae, with a simultaneous measurement of force (Frank–Starling mechanism) and Ca2+ transients (CaT) or transmembrane action potentials (AP). Over the entire length-range studied, the duration of isometric contraction, CaT and AP, were shorter in the RA myocardium than in the RV myocardium. The RA myocardium was stiffer than the RV myocardium. With the increasing length of the RA and RV myocardium, the amplitude and duration of isometric contraction and CaT increased, as well as the amplitude and area of the “CaT difference curves” (shown for the first time). However, the rates of the tension development and relaxation decreased. No contribution of AP duration to the heterometric regulation of isometric tension was found in either the RA or RV myocardium of the guinea pig. Changes in the degree of overlap of the contractile proteins of the guinea pig RA and RV myocardium mainly affect CaT kinetics but not AP duration.

A Novel Ultrasound Elastography Configuration for Simultaneous Measurement of Contact Forces

A Novel Ultrasound Elastography Configuration for Simultaneous Measurement of Contact Forces

Shape-Morphing Dynamics of Soft Compliant Membranes for Drag and Turbulence Modulation.

We study the kinematics and dynamics of a highly compliant membrane disk placed head-on in a uniform flow. With increasing flow velocity, the membrane deforms nonlinearly into increasingly parachutelike shapes. These aerodynamically elongated materials exhibit a modified drag law, which is linked to the elastohydrodynamic interactions. We predict the unsteady structural response of the membranes using a nonlinear, aeroelastic model-in excellent agreement with experimental measurements of deformations and force fluctuations. With simultaneous membrane interface tracking, force measurements and flow tracing, we reveal that a peculiar skewness in the membrane's oscillations triggers turbulence production in the wake, thereby modulating the drag. The present work provides a demonstration of the complex interplay between soft materials and fluid turbulence, leading to new, emergent system properties.

Force generation in human blood platelets by filamentous actomyosin structures

Blood platelets are central elements of the blood clotting response after wounding. Upon vessel damage, they bind to the surrounding matrix and contract the forming thrombus, thus helping to restore normal blood circulation. The hemostatic function of platelets is directly connected to their mechanics and cytoskeletal organization. The reorganization of the platelet cytoskeleton during spreading occurs within minutes and leads to the formation of contractile actomyosin bundles, but it is not known if there is a direct correlation between the emerging actin structures and the force field that is exerted to the environment. In this study, we combine fluorescence imaging of the actin structures with simultaneous traction force measurements in a time-resolved manner. In addition, we image the final states with superresolution microscopy. We find that both the force fields and the cell shapes have clear geometrical patterns defined by stress fibers. Force generation is localized in a few hotspots, which appear early during spreading, and, in the mature state, anchor stress fibers in focal adhesions. Moreover, we show that, for a gel stiffness in the physiological range, force generation is a very robust mechanism and we observe no systematic dependence on the amount of added thrombin in solution or fibrinogen coverage on the substrate, suggesting that force generation after platelet activation is a threshold phenomenon that ensures reliable thrombus contraction in diverse environments.

Differences in Effects of Length-Dependent Regulation of Force and Ca2+ Transient in the Myocardial Trabeculae of the Rat Right Atrium and Ventricle.

The comparative differences in the fundamental mechanisms of contractility regulation and calcium handling of atrial and ventricular myocardium remain poorly studied. An isometric force-length protocol was performed for the entire range of preloads in isolated rat right atrial (RA) and ventricular (RV) trabeculae with simultaneous measurements of force (Frank-Starling mechanism) and Ca2+ transients (CaT). Differences were found between length-dependent effects in RA and RV muscles: (a) the RA muscles were stiffer, faster, and presented with weaker active force than the RV muscles throughout the preload range; (b) the active/passive force-length relationships were almost linear for the RA and RV muscles; (c) the value of the relative length-dependent growth of passive/active mechanical tension did not differ between the RA and RV muscles; (d) the time-to-peak and amplitude of CaT did not differ between the RA and RV muscles; (e) the CaT decay phase was essentially monotonic and almost independent of preload in the RA muscles, but not in the RV muscles. Higher peak tension, prolonged isometric twitch, and CaT in the RV muscle may be the result of higher Ca2+ buffering by myofilaments. The molecular mechanisms that constitute the Frank-Starling mechanism are common in the rat RA and RV myocardium.

Simultaneous Force and Darkfield Measurements Reveal Solvent-Dependent Axial Control of Optically Trapped Gold Nanoparticles

Single molecule force spectroscopy using optical tweezers (OT) has enabled nanoresolved measurements of dynamic biological processes but not of synthetic molecular mechanisms. Standard OT probes made from silica or polystyrene are incompatible with trapping in organic solvents for solution phase chemistry or with force-detected absorption spectroscopies. Here, we demonstrate optical trapping of gold nanoparticles in both aqueous and organic conditions using a custom OT and darkfield instrument which can uniquely measure force and scattering spectra of single gold nanoparticles (Au NPs) simultaneously. Our work reveals that standard models of trapping developed for aqueous conditions cannot account for the trends observed in different media here. We determine that higher pushing forces mitigate the increase in trapping force in higher index organic solvents and lead to axial displacement of the particle which can be controlled through trap intensity. This work develops a new model framework incorporating axial forces for understanding nanoparticle dynamics in an optical trap. These results establish the combined darkfield OT with Au NPs as an effective OT probe for single molecule and single particle spectroscopy experiments, with three-dimensional nanoscale control over NP location.

Dynamic Behavior and Insertional Forces of a Precurved Electrode Using the Pull-Back Technique in a Fresh Microdissected Cochlea.

This study evaluated the utility of the pull-back technique in improving perimodiolar positioning of a precurved cochlear implant (CI) electrode array (EA) with simultaneous insertion force profile measurement and direct observation of dynamic EA behavior. Precurved EAs with perimodiolar positioning have improved outcomes compared with straight EAs because of lowered charge requirements for stimulation and decreased spread of excitation. The safety and efficacy of the pull-back technique in further improving perimodiolar positioning and its associated force profile have not been adequately demonstrated. The bone overlying the scala vestibuli was removed in 15 fresh cadaveric temporal bones, leaving the scala tympani unviolated. Robotic insertions of EAs were performed with simultaneous force measurement and video recording. Force profiles were obtained during standard insertion, overinsertion, and pull-back. Postinsertion CT scans were obtained during each of the three conditions, enabling automatic segmentation and calculation of angular insertion depth, mean perimodiolar distance ( Mavg ), and cochlear duct length. Overinsertion did not result in significantly higher peak forces than standard insertion (mean [SD], 0.18 [0.06] and 0.14 [0.08] N; p = 0.18). Six temporal bones (40%) demonstrated visibly improved perimodiolar positioning after the protocol, whereas none worsened. Mavg significantly improved after the pull-back technique compared with standard insertion (mean [SD], 0.34 [0.07] and 0.41 [0.10] mm; p < 0.01). The pull-back technique was not associated with significantly higher insertional forces compared with standard insertion. This technique was associated with significant improvement in perimodiolar positioning, both visually and quantitatively, independent of cochlear size.

Simultaneous magnetic field and field gradient mapping of hexagonal MnNiGa by quantitative magnetic force microscopy

Magnetic force microscopy (MFM) is a scanning microscopy technique that is commonly employed to probe the sample’s magnetostatic stray fields via their interaction with a magnetic probe tip. In this work, a quantitative, single-pass MFM technique is presented that maps one magnetic stray-field component and its spatial derivative at the same time. This technique uses a special cantilever design and a special high-aspect-ratio magnetic interaction tip that approximates a monopole-like moment. Experimental details, such as the control scheme, the sensor design, which enables simultaneous force and force gradient measurements, as well as the potential and limits of the monopole description of the tip moment are thoroughly discussed. To demonstrate the merit of this technique for studying complex magnetic samples it is applied to the examination of polycrystalline MnNiGa bulk samples. In these experiments, the focus lies on mapping and analyzing the stray-field distribution of individual bubble-like magnetization patterns in a centrosymmetric [001] MnNiGa phase. The experimental data is compared to calculated and simulated stray-field distributions of 3D magnetization textures, and, furthermore, bubble dimensions including diameters are evaluated. The results indicate that the magnetic bubbles have a significant spatial extent in depth and a buried bubble top base.

A versatile and high-throughput flow-cell system combined with fluorescence imaging for simultaneous single-molecule force measurement and visualization.

A flow-cell offers many advantages for single-molecule studies. But, its merit as a quantitative single-molecule tool has long been underestimated. In this work, we developed a gas-pumped fully calibrated flow-cell system combined with fluorescence imaging for simultaneous single-molecule force measurement and visualization. Such a flow-cell system has considered the hydrodynamic drags on biomolecules and hence can apply and measure force up to more than 100 pN in sub-pN precision with an ultra-high force stability (force drift <0.01 pN in 10 minutes) and tuning accuracy (∼0.04 pN). Meanwhile, it also allows acquiring force signals and fluorescence images at the same time, parallelly tracking hundreds of protein motors in real time as well as monitoring the conformational changes of biomolecules under a well-controlled force, as demonstrated by a series of single-molecule experiments in this work, including the studies of DNA overstretching dynamics, transcription under force and DNA folding/unfolding dynamics. Interesting findings, such as the very tight association of single-stranded binding (SSB) proteins with ssDNA and the reversed transcription, have also been made. These results together lay down an essential foundation for a flow-cell to be used as a versatile, quantitative and high-throughput tool for single-molecule manipulation and visualization.

A new way to determine the indicators of vertical and horizontal of a subway car

The issues of measuring the coefficients of vertical and horizontal dynamics of a subway car during running dynamic tests are reviewed. The theoretical research of bogie frame loading by finite element method has been done. Analysis of complex calculation outcomes and stress distribution diagrams on bogie frame under the action of vertical, longitudinal, and lateral forces has allowed defining the place of strain gauges installation on the elements of the bogie and the signal processing method for measuring vertical and lateral forces acting on bogie frame of the subway car. The new measuring circuit with strain gauges connected in two full bridges with a four-wire connection scheme will provide simultaneous measurement of vertical and lateral forces acting on the subway car bogie frame. The running tests on the evaluation of dynamic qualities of subway car model 81-714Uz confirmed the effectiveness of the developed measuring scheme for determining the indicators of vertical and horizontal dynamics of a subway car.

Real-time monitoring of the contractile properties of H9C2 cardiomyocytes by double resonator piezoelectric cytometry.

Testing the mechanical properties of cardiomyocytes plays an important role in the study of the physiological and pathological processes of constant contraction and diastole of the cardiovascular system. However, there is currently no satisfactory and dynamic technology to measure the mechanical properties of cardiomyocytes in a sustained manner, greatly affecting their practical application in clinical diagnosis and treatment evaluation. Herein, a double resonator piezoelectric cytometry (DRPC) technique was employed for dynamic monitoring of H9C2 cardiomyocyte adhesion and the effects of two cardiovascular drugs on the contractile properties of H9C2 cardiomyocytes, i.e., isoprenaline (ISO, a positive inotropic agent) and verapamil (VRP, a negative inotropic agent). Specifically, we used 9 MHz AT and BT-cut bare gold and transparent ITO electrodes and compared their dynamic adhesion to the two electrodes modified with RGD and gelatin respectively versus unmodified to measure the cell generated stress (ΔS) exerted on the quartz crystal surface by a population of cells and the cell viscoelastic index (CVI). We found that the DRPC technique can quantitatively measure the magnitude and direction of the generated forces during the adhesion process of the cells and under the effect of drugs. In conclusion, the technique presented in this study can be used for the simultaneous measurement of cell adhesion, traction force and viscoelasticity of living cells in a noninvasive, dynamic and continuous way, making it an ideal tool for assessing the population contractility of cardiomyocytes and evaluating the efficacy and toxicity of cardiovascular drugs.

APPLICATION OF COERCYTIMETRY METHOD FOR EVALUATION OF RESIDUAL STRESSES IN FLAT KNIVES

With the help of high-frequency currents, hardening coatings of increased hardness are applied to the working bodies of agricultural machines. When evaluating the effectiveness of these methods, along with studying the basic physical and mechanical properties of coatings, it is necessary to know the level of residual stresses in the coatings obtained. (Research purpose) The research purpose is studying the features and evaluate the possibilities of using coercimetry as an objective and reliable method for determining the stress state of flat knives hardened by HDPE boration. (Materials and methods) Samples of 65G steel in the initial state and flat mower knives reinforced with HDPE boration were prepared for the study. Performed the work in accordance with the current GOST 58599-2019 "Technical diagnostics. Diagnostics of steel structures. Magnetic coercive method. General requirements". Bursting machines, a magnetic structroscope (coercitimeter) were used KRM-C-K2M and devices for determining hardness and microstructure. (Results and discussion) At the first stage, the expected values of the coercive force for 65G steel were calculated depending on the chemical composition. As a result of mechanical tests of 65G steel samples for tensile strength with simultaneous measurement of coercive force, experimental data were obtained for constructing calibration curves, which were used to determine stresses in hardened knife samples after HDPE boration. It was determined that the residual stresses in hardened flat knives vary from 400 to 730 megapascals. These stresses can be considered acceptable (safe), since the yield strength for 65G steel is 685-785 megapascals. (Conclusions) The method of measuring coercive force makes it possible to estimate the degree of change in residual stresses in parts hardened by HDPE boration methods.

A test rig for the full characterization of the dynamics of shrouded turbine blades

Highly stressed forced vibrations experienced by Low Pressure Turbine (LPT) blades during their operation can result in high cycle fatigue (HCF) which can ultimately lead to failure. To avoid this occurrence, the vibration amplitudes must be anticipated and reduced. This is generally done by employing friction damping devices like under-platform dampers, shrouds and snubbers. In case of blades with shrouds at their tips, the adjacent shrouded blades are coupled to each other and three-dimensional periodic shroud contact forces acting on shrouds significantly influence the vibration amplitudes as energy is dissipated due to friction. Hence, for the experimental validation of the numerical contact models that are used for the prediction of nonlinear forced response of shrouded blades, it is equally necessary to measure the contact forces acting at the shrouds. Moreover, present-day requirement of more accurate and detailed models requires thorough and comprehensive experimental validation calling for the measurement of three-dimensional shroud contact forces from purposely designed test rigs.This study presents the design, development and operation of an experimental test rig that allows full characterization of the dynamics of shrouded turbine blade, i.e., simultaneous measurement of three-dimensional shroud contact forces and shrouded blade forced response. The starting point was the design of the test rig components based on the design requirements. This is followed by the description of the major components of the proposed test rig i.e., the three-dimensional contact force measurement system and the torque screw mechanism. In the subsequent section, the details of the experimental setup to measure the forced response and three-dimensional shroud contact forces simultaneously are highlighted as the test campaign is performed for different normal preloads and excitation force levels. Consequently, the effects of the variation in the normal preload and excitation force on the measured response and shroud contact forces are discussed. Finally, it is shown how the results establish the efficacy of the proposed test rig in providing a comprehensive depiction of the dynamic response of the shrouded blade and 3D shroud contact forces that will result in more accurate and reliable experimental validation of numerical tools.

Increasing the Life Span of Tools Applied in Cheese Cutting Machines via Appropriate Micro-Blasting

The potential to increase the life span of tools applied in cheese cutting machines is of great importance, considering their cost and the risk of fragmented metallic parts of the tool being inserted into the cheese. Such tools are commonly manufactured using stainless steel 405 and are subjected to dynamic loads during their operation, leading to fatigue failure. An efficient method to improve the fatigue properties of such tools is the application of micro-blasting. In this work, for the first time, an experimental–analytical methodology was developed for determining optimum micro-blasting conditions and ascertaining a preventive replacement of the tool before its extensive fracture. This methodology is based on the construction of a pneumatic system for the precise cutting of cheese and simultaneous force measurements. Additionally, the entire cheese-cutting process is simulated by appropriate FEA modeling. According to the attained results, micro-blasting on steel tools significantly improves the resistance against dynamic loads, whilst the number of impacts that a tool can withstand until fatigue fracture is more than three times larger. Via the developed methodology, a preventive replacement of the tool can be conducted, avoiding the risk of a sudden tool failure. The proposed methodology can be applied to different tool geometries and materials.

A smart Li-ion battery with self-sensing capabilities for enhanced life and safety

Accurate monitoring and prediction of the operating status of Li-ion batteries (LiBs) are essential for enhancing the longevity and safety of LiB-powered applications. In contrast to conventional battery management strategies that rely solely on voltage, current, and temperature at module level, we present a smart Li-ion cell with an integrated fiber Bragg grating (FBG) optical fiber sensor that enables simultaneous measurement of temperature, force, and displacement at the cell level with a simple beam structure. The Li-ion smart battery sensor scheme realizes the synchronous monitoring of battery mechanical, electrical and thermal multi-physics parameters. We demonstrate that monitoring force is beneficial for enhancing cell life and safety. Specifically, the evolution of peak force upon cycling correlates linearly with the capacity fade, making the force signal a useful state-of-health indicator. Further, the change in cell force is tens of seconds earlier than the change in cell temperature under nail penetration and thermal abuse tests, exhibiting enormous potential for early detection of battery safety incidents, using the Li-ion smart battery scheme, we realize the quantitative description of the evolution of battery structure. By the Li-ion smart battery, it has the ability to improve the quality, reliability and service life of the battery.

Abstract P1057: Implementing A Novel FRET-Based Myofilament Activation Biosensor To Interrogate Dynamic Cardiac Sarcomere Performance With Small Molecule And Genetic Manipulations During A Physiological Twitch

The sarcomere is the functional unit of cardiac muscle contraction. Understanding the precise mechanisms regulating this contraction is key to advancing insights into cardiomyopathies, which affect as many as 1 in 500 adults. Previous work has identified many key sarcomeric components and modulators necessary for the activation of contraction through inter-myofilament signaling. Although these studies have provided valuable information, the majority of this work has been done using in vitro protein recombination or permeabilized muscle. While informative, these systems lack significant physiological features of muscle, including load and intact excitation-contraction coupling mechanisms. Therefore, a large gap exists in the ability to monitor the time-sensitive stepwise physiological mechanism of muscle sarcomere activation in an intact system in real time. In order to further advance the study of sarcomere activation in both physiological and disease states, a cardiac specific myofilament-targeted FRET based biosensor has been designed and validated. The sarcomere activation biosensor reports myofilament dynamics during physiological twitch contractions in live cardiac muscle in real time in the form of simultaneous force and fluorescence measurements. This allows FRET-detection of the global conformational changes in TnC, a nexus point able to integrate many sarcomere-activating ligands, to be observed. From these changes in fluorescence the ensemble of events which lead to sarcomere activation and muscle contraction can be tracked. Data show regulatory ligands of myofilament activation in real time during a physiological twitch contraction. Currently, the biosensor is being utilized to investigate changes in sarcomere activation driven through the use of small molecules, including myosin inhibitor Mavacamten and TnC-TnI inhibitor W7, and those seen in MyBP-C knockout mice. The results of these investigations will be discussed.

A dual LC resonant circuit integrated wireless passive force and temperature sensor for harsh-environment applications

This paper proposes a dual inductor-capacitor (LC) circuit integrated wireless and passive force and temperature sensor for the simultaneous measurement of force and temperature in high-temperature environments. The sensor is fabricated by a two-step process: the preparation of the Al2O3 substrate and the fabrication of the dual LC sensor with Ag paste using screen-printing technology and metallization. The variation in ambient force and temperature can be detected wirelessly by extracting the resonant frequencies of the antenna. The sensor can work in the force range of 0–10 N and temperature range of 25–500 °C with a maximum force sensitivity of 107 kHz/N at 500 °C and temperature sensitivity of 21.7 kHz/°C. To precisely measure the force, the temperature compensation method is proposed. The sensor has the advantages of low cost, simple fabrication and test, and high stability and repeatability, which are promising for the force and temperature application on the engine turbine blade in high-temperature environments.