scholarly journals High-force magnetic tweezers with hysteresis-free force feedback

2019 ◽  
Author(s):  
D. Kah ◽  
C. Dürrbeck ◽  
W. Schneider ◽  
B. Fabry ◽  
R. C. Gerum
Keyword(s):  
Force Feedback ◽  
Magnetic Hysteresis ◽  
Iron Alloy ◽  
Magnetic Tweezers ◽  
Core Material ◽  
Magnetic Field Measurement ◽  
Exponential Relationship ◽  
Plastic Properties ◽  
Magnetic Tweezer ◽  
Elastic And Plastic Deformations

ABSTRACTMagnetic tweezers based on solenoids with iron alloy cores are widely used to apply large forces (~100 nN) onto micron-sized (~5 μm) superparamagnetic particles for mechanical manipulation or microrheological measurements at the cellular and molecular level. The precision of magnetic tweezers, however, is limited by the magnetic hysteresis of the core material, especially for time-varying force protocols. Here, we eliminate magnetic hysteresis by a feedback control of the magnetic induction, which we measure with a Hall sensor mounted to the distal end of the solenoid core. We find that the generated force depends on the induction according to a power-law relationship, and on the bead-tip distance according to a stretched exponential relationship. Together, both relationships allow for an accurate force calibration and precise force feedback with only 3 calibration parameters. We apply our method to measure the force-dependence of the viscoelastic and plastic properties of fibroblasts using a protocol with stepwise increasing and decreasing forces. We find that soft cells show an increasing stiffness but decreasing plasticity at higher forces, indicating a pronounced stress stiffening of the cytoskeleton. By contrast, stiff cells show no stress stiffening but an increasing plasticity at higher forces. These findings indicate profound differences between soft and stiff cells regarding their protection mechanisms against external mechanical stress. In summary, our method increases the precision, simplifies the handling and extends the applicability of magnetic tweezers.SIGNIFICANCEMagnetic tweezers are widely used, versatile tools to investigate the mechanical behavior of cells or to measure the strength of receptor-ligand bonds. A limitation of existing high-force magnetic tweezer setups, however, is caused by the magnetic hysteresis of the tweezer core material. This magnetic hysteresis requires that the tweezer core must be de-magnetized (de-Gaussed) prior to each measurement, and that flexible force protocols with decreasing forces are not possible. We describe how these limitations can be overcome with a force feedback though direct magnetic field measurement. We demonstrate the applicability of our setup by investigating the visco-elastic and plastic deformations of fibroblasts to forces of different amplitudes.

Magnetic bead microrheology

2018 ◽  
Author(s):  
Eric M. Furst ◽  
Todd M. Squires
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Particles ◽  
Colloidal Particles ◽  
Permanent Magnets ◽  
Operating Regime ◽  
Magnetic Bead ◽  
Magnetic Tweezers ◽  
Linear Measurements ◽  
Magnetic Forces ◽  
Magnetic Tweezer

Magnetism is a convenient force for actively pulling colloidal particles in a material. Many materials of interest in a microrheology experiment have a negligible magnetic susceptibility, and so embedded magnetic particles can be subject to relatively strong forces by fields imposed from outside of the sample. These are usually generated by electromagnets, but can also include the use of permanent magnets, or a combination of both. Such “magnetic tweezers” are used as sensitive force probes, capable of generating forces ranging from femtonewtons to nanonewtons. Magnetic forces and magnetic materials are reviewed and magnetic tweezer designs discussed. Linear and non-linear measurements using magnetic tweezers are presented, including studies yield stress and shear thinning. The operating regime of magnetic tweezer microrheology is presented, which enables microrheology experiments to access stiffer materials.

scholarly journals High-Force Magnetic Tweezers with Hysteresis-Free Force Feedback

2020 ◽  
Vol 119 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Delf Kah ◽  
Christopher Dürrbeck ◽  
Werner Schneider ◽  
Ben Fabry ◽  
Richard Carl Gerum
Keyword(s):  
Force Feedback ◽  
Magnetic Tweezers

203. An apparatus for measuring the elastic and plastic properties of cheese curd

1938 ◽  
Vol 9 (3) ◽  
pp. 347-350 ◽  
Author(s):  
G. W. Scott Blair
Keyword(s):  
Shear Modulus ◽  
Compressive Load ◽  
Optimum Time ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Single Criterion ◽  
Elastic And Plastic Deformations ◽  
Cheese Curd

An apparatus is described for measuring the elastic and plastic deformations of cheese curd under a compressive load at the time when it is ready for cutting. A figure inversely proportional to shear modulus can be obtained with considerable accuracy, and is believed to serve as the best single criterion of “firmness” in deciding the optimum time to cut the curd.

scholarly journals Application of a Nonlinear Hammerstein-Wiener Estimator in the Development and Control of a Magnetorheological Fluid Haptic Device for Robotic Bone Biopsy

Actuators ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 83 ◽  
Author(s):  
Elnaz Shokrollahi ◽  
Andrew Goldenberg ◽  
James Drake ◽  
Kyle Eastwood ◽  
Matthew Kang
Keyword(s):  
Force Feedback ◽  
Bone Biopsy ◽  
Magnetic Hysteresis ◽  
Magnetorheological Fluid ◽  
Hysteretic Behavior ◽  
Force Measurements ◽  
Loop Control ◽  
Feedback Information ◽  
Wide Range ◽  
Loop Control System

A force generator module (FGM) based on magnetorheological fluid (MRF) was developed to provide force-feedback information for applications in tele-robotic bone biopsy procedures. The FGM is capable of rapidly re-producing a wide range of forces that are common in bone biopsy applications. As a result of the nonlinear nature of MRF, developing robust controllers for these mechanisms can be challenging. In this paper, we present a case study motivated by robotic bone biopsy. We use a non-linear Hammerstein-Wiener (H-W) estimator to address this challenge. The case is presented through three studies. First, an experiment to develop design constraints is presented and describes biopsy force measurements for various animal tissues. Required output forces were found to range between <1 N and <50 N. A second study outlines the design of the FGM and presents the experimental characterization of the hysteretic behavior of the MRF. This data is then used as estimators and validators to develop the nonlinear Hammerstein-Wiener (H-W) model of the MRF. Validation experiments found that the H-W model is capable of predicting the behavior of the MRF device with 95% accuracy and can eliminate hysteresis in a closed-loop control system. The third study demonstrates the FGM used in a 1-DOF haptic controller in a simulated robotic bone-biopsy. The H-W control tracked the input signal while compensating for magnetic hysteresis to achieve optimal performance. In conclusion, the MRF-based device can be used in surgical robotic operations that require a high range of force measurements.

High-resolution scanning electron microscopy of thin-film magnetic media of magnetic recording disk

1992 ◽  
Vol 50 (2) ◽  
pp. 1334-1335
Author(s):  
K. Ogura ◽  
H. Nishioka ◽  
N. Ikeo ◽  
T. Kanazawa ◽  
J. Teshima
Keyword(s):  
Thin Film ◽  
Fine Structure ◽  
High Resolution ◽  
Magnetic Recording ◽  
High Performance ◽  
Magnetic Hysteresis ◽  
Grain Structure ◽  
Magnetic Media ◽  
Cross Sectional ◽  
Resolution Observation

Structural appraisal of thin film magnetic media is very important because their magnetic characters such as magnetic hysteresis and recording behaviors are drastically altered by the grain structure of the film. However, in general, the surface of thin film magnetic media of magnetic recording disk which is process completed is protected by several-nm thick sputtered carbon. Therefore, high-resolution observation of a cross-sectional plane of a disk is strongly required to see the fine structure of the thin film magnetic media. Additionally, observation of the top protection film is also very important in this field.Recently, several different process-completed magnetic disks were examined with a UHR-SEM, the JEOL JSM 890, which consisted of a field emission gun and a high-performance immerse lens. The disks were cut into approximately 10-mm squares, the bottom of these pieces were carved into more than half of the total thickness of the disks, and they were bent. There were many cracks on the bent disks. When these disks were observed with the UHR-SEM, it was very difficult to observe the fine structure of thin film magnetic media which appeared on the cracks, because of a very heavy contamination on the observing area.

EFFECT OF ADDITION OF THIRD ELEMENT IN HIGH SILICON-IRON ALLOY

1988 ◽  
Vol 49 (C8) ◽  
pp. C8-133-C8-134
Author(s):  
H. Nakamura ◽  
N. Tsuya ◽  
Y. Saito ◽  
Y. Katsumata ◽  
Y. Harada
Keyword(s):  
Iron Alloy ◽  
Silicon Iron ◽  
High Silicon

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

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