Generation mechanism and empirical model of eddy current force and torque in drum-type eddy current separation

Enhancing the recovery efficiency of non-ferrous metals in eddy current separation is of great significance. In this study, the accuracy of the simulation model was verified by comparing the eddy current force. The transformation mechanism of the Lorentz forces into the eddy current force and torque in non-ferrous metal particles was revealed by analyzing various physical fields. Then, the influence of magnetic field parameters on eddy current, eddy current force, and torque was studied. It shows that the eddy current force and torque are affected by the vector gradient of the magnetic field and the magnetic flux density, respectively. Additionally, the time derivative of the magnetic field impacts the magnitude of the eddy current force and torque by controlling the eddy current. On this basis, the empirical models of eddy current force and torque were established by similarity theory. The results obtained can improve and expand the application of eddy current separation.

Is activation of the vestibular system by electromagnetic induction a possibility in an MRI context?

In recent years, an increasing number of studies have discussed the mechanisms of vestibular activation in strong magnetic field settings such as occur in a magnetic resonance imaging scanner environment. Amid the different hypotheses, the Lorentz force explanation currently stands out as the most plausible mechanism, as evidenced by activation of the vestibulo-ocular reflex. Other hypotheses have largely been discarded. Nonetheless, both human data and computational modeling suggest that electromagnetic induction could be a valid mechanism which may coexist alongside the Lorentz force. To further investigate the induction hypothesis, we provide, herein, a first of its kind dosimetric analysis to estimate the induced electric fields at the vestibular system and compare them with what galvanic vestibular stimulation would generate. We found that electric fields strengths from induction match galvanic vestibular stimulation strengths generating vestibular responses. This review examines the evidence in support of electromagnetic induction of vestibular responses, and whether movement-induced time-varying magnetic fields should be further considered and investigated.

Fano cavity test and investigation of the response of the Roos chamber irradiated by proton beams in perpendicular magnetic fields up to 1 T

Objective. The aim of this work is to investigate the response of the Roos chamber (type 34001) irradiated by clinical proton beams in magnetic fields.Approach. At first, a Fano test was implemented in Monte Carlo software package GATE version 9.2 (based on Geant4 version 11.0.2) using a cylindrical slab geometry in a magnetic field up to 1 T. In accordance to an experimental setup (Fuchset al2021), the magnetic field correction factorskQB⃗of the Roos chamber were determined at different energies up to 252 MeV and magnetic field strengths up to 1 T, by separately simulating the ratios of chamber signalsMQ/MQB⃗,without and with magnetic field, and the dose-conversion factorsDw,QB⃗/Dw,Qin a small cylinder of water, with and without magnetic field. Additionally, detailed simulations were carried out to understand the observed magnetic field dependence.Main results. The Fano test was passed with deviations smaller than 0.25% between 0 and 1 T. The ratios of the chamber signals show both energy and magnetic field dependence. The maximum deviation of the dose-conversion factors from unity of 0.22% was observed at the lowest investigated proton energy of 97.4 MeV andB⃗= 1 T. The resultingkQB⃗factors increase initially with the applied magnetic field and decrease again after reaching a maximum at around 0.5 T; except for the lowest 97.4 MeV beam that show no observable magnetic field dependence. The deviation from unity of the factors is also larger for higher proton energies, where the maximum lies at 1.0035(5), 1.0054(7) and 1.0069(7) for initial energies ofE0= 152, 223.4 and 252 MeV, respectively.Significance. Detailed Monte Carlo studies showed that the observed effect can be mainly attributed to the differences in the transport of electrons produced both outside and inside of the air cavity in the presence of a magnetic field.

Wireless Magnetoelectrochemical Induction of Rotational Motion

Electromagnetically induced rotation is a key process of many technological systems that are used in daily life, especially for energy conversion. In this context, the Lorentz force-induced deviation of charges is a crucial physical phenomenon to generate rotation. Herein, they combine the latter with the concept of bipolar electrochemistry to design a wireless magnetoelectrochemical rotor. Such a device can be considered as a wet analog of a conventional electric motor. The main driving force that propels this actuator is the result of the synergy between the charge-compensating ion flux along a bipolar electrode and an external magnetic field applied orthogonally to the surface of the object. The trajectory of the wirelessly polarized rotor can be controlled by the orientation of the magnetic field relative to the direction of the global electric field, producing a predictable clockwise or anticlockwise motion. Fine-tuning of the applied electric field allows for addressing conducting objects having variable characteristic lengths.

On Thermal and Electrodynamic Aspects of the Superconductive Transition Process

In a classic paper of 1960, W. H. Cherry and J. I. Gittleman discussed various thermal and electrodynamic aspects of the superconductive transition process relevant to practical applications. In a section of the paper that has remained unnoticed, they proposed a physical model for the Meissner effect. Earlier in 1940-1943, in work that has also remained unnoticed, K. M. Koch had introduced related physical ideas to explain the Meissner effect. Still earlier in 1937, J. C. Slater proposed a model to explain the perfect diamagnetism of superconductors. None of these ideas are part of the conventional London-BCS understanding of superconductivity, yet I will argue that they are essential to understand the Meissner effect, the most fundamental property of superconductors. The unconventional theory of hole superconductivity unifies and extends these ideas. A key missing element in the conventional theory as well as in these early theories is electron-hole asymmetry. A proper understanding of the Meissner effect may help with practical applications of superconductors, as well as to find new superconducting materials with desirable properties.

On the optimized energy transport rate of magnetized micropolar fluid via ternary hybrid ferro-nanosolids: A numerical report

In the current era, a chemical, industrial, or production process may not be devoid of heat transfer processes through fluids. This is seen in evaporators, distillation units, dryers, reactors, refrigeration and air conditioning systems, and others. On the other hand, the micropolar model effectively simulates microstructured fluids like animal blood, polymeric suspensions, and crystal fluid, paving the way for new potential applications based mainly on complex fluids. This investigation attempts to figure out and predict the thermal behavior of a polar fluid in motion across a solid sphere while considering the Lorentz force and mixed convection. To support the original fluid's thermophysical characteristics, two types of ternary hybrid ferro-nanomaterials are used. The problem is modelled using a single-phase model. Then, using the Keller box approximation, a numerical finding is obtained. The study reveals that Increasing the volume fraction of the ternary hybrid nonsolid results in optimized values of Nusselt number, velocity, and temperature. The presence of Lorentz forces effectively mitigates flow strength, skin friction, and energy transfer rate. The mixed convection factor contributes significantly to enhanced energy transfer and improved flow scenarios. For maximum heat transfer efficiency, employing Fe3O4-Cu-SiO2 is recommended over Fe3O4-Al2O3-TiO2.

Dual function of magnetic field in enhancing antibiotic wastewater treatment by an integrated photocatalysis and fluidized bed biofilm reactor (FBBR)

The integrated photocatalysis and fluidized bed biofilm reactor (FBBR) is an attractive wastewater treatment technique for managing wastewater containing antibiotics. However, the fast recombination of photoinduced charge and low microbial activity limit the degradation and mineralization efficiency for antibiotics. To address this, we attempt to introduce magnetic field (MF) to the integrated system with B-doped Bi3O4Cl as the photocatalysts to effectively improve removal and mineralization of ciprofloxacin (CIP). As a consequence, the degradation rate reaches 96% after 40 d in integrated system with MF. The biofilm inside the integrated system with MF carrier can mineralize the photocatalytic products, thereby increasing the total organic carbon (TOC) degradation rate by more than 32%. The electrochemical experiment indicates the Lorentz force generated by MF can accelerate charge separation, increasing the electron concentration. Simultaneously, the increased amounts of electrons lead to the generation of more ·OH and ·O2-. MF addition also results in increased biomass, increased biological respiratory activity, microbial community evolution and accelerated microbial metabolism, enabling more members to biodegrade photocatalytic intermediates. Therefore, applied MF is an efficient method to enhance CIP degradation and mineralization by the integrated system.

Longer duration entry mitigates nystagmus and vertigo in 7-Tesla MRI

Introduction

Patients and technologists commonly describe vertigo, dizziness, and imbalance near high-field magnets, e.g., 7-Tesla (T) magnetic resonance imaging (MRI) scanners. We sought a simple way to alleviate vertigo and dizziness in high-field MRI scanners by applying the understanding of the mechanisms behind magnetic vestibular stimulation and the innate characteristics of vestibular adaptation.

Methods

We first created a three-dimensional (3D) control systems model of the direct and indirect vestibulo-ocular reflex (VOR) pathways, including adaptation mechanisms. The goal was to develop a paradigm for human participants undergoing a 7T MRI scan to optimize the speed and acceleration of entry into and exit from the MRI bore to minimize unwanted vertigo. We then applied this paradigm from the model by recording 3D binocular eye movements (horizontal, vertical, and torsion) and the subjective experience of eight normal individuals within a 7T MRI. The independent variables were the duration of entry into and exit from the MRI bore, the time inside the MRI bore, and the magnetic field strength; the dependent variables were nystagmus slow-phase eye velocity (SPV) and the sensation of vertigo.

Results

In the model, when the participant was exposed to a linearly increasing magnetic field strength, the per-peak (after entry into the MRI bore) and post-peak (after exiting the MRI bore) responses of nystagmus SPV were reduced with increasing duration of entry and exit, respectively. There was a greater effect on the per-peak response. The entry/exit duration and peak response were inversely related, and the nystagmus was decreased the most with the 5-min duration paradigm (the longest duration modeled). The experimental nystagmus pattern of the eight normal participants matched the model, with increasing entry duration having the strongest effect on the per-peak response of nystagmus SPV. Similarly, all participants described less vertigo with the longer duration entries.

Conclusion

Increasing the duration of entry into and exit out of a 7T MRI scanner reduced or eliminated vertigo symptoms and reduced nystagmus peak SPV. Model simulations suggest that central processes of vestibular adaptation account for these effects. Therefore, 2-min entry and 20-s exit durations are a practical solution to mitigate vertigo and other discomforting symptoms associated with undergoing 7T MRI scans. In principle, these findings also apply to different magnet strengths.

Influence of Traps and Lorentz Force on Charge Transport in Organic Semiconductors

Charge transport characteristics in organic semiconductor devices become altered in the presence of traps due to defects or impurities in the semiconductors. These traps can lead to a decrease in charge carrier mobility and an increase in recombination rates, thereby ultimately affecting the overall performance of the device. It is therefore important to understand and mitigate the impact of traps on organic semiconductor devices. In this contribution, the influence of the capture and release times of trap states, recombination rates, and the Lorentz force on the net charge of a low-mobility organic semiconductor was determined using the finite element method (FEM) and Hall effect method through numerical simulations. The findings suggest that increasing magnetic fields had a lesser impact on net charge at constant capture and release times of trap states. On the other hand, by increasing the capture time of trap states at a constant magnetic field and fixed release time, the net charge extracted from the semiconductor device increased with increasing capture time. Moreover, the net charge extracted from the semiconductor device was nearly four and eight times greater in the case of the non-Langevin recombination rates of 0.01 and 0.001, respectively, when compared to the Langevin rate. These results imply that the non-Langevin recombination rate can significantly enhance the performance of semiconductor devices, particularly in applications that require efficient charge extraction. These findings pave the way for the development of more efficient and cost-effective electronic devices with improved charge transport properties and higher power conversion efficiencies, thus further opening up new avenues for research and innovation in this area of modern semiconductor technology.

Remote targeted electrical stimulation

Objective:The ability to generate electric fields in specific targets remotely would transform manipulations of processes that rest on electrical signaling.Approach:This article shows that focal electric fields are generated from distance by combining two orthogonal, remotely applied energies-magnetic and focused ultrasonic fields. The effect derives from the Lorentz force equation applied to magnetic and ultrasonic fields.Main results:We elicited this effect using standard hardware and confirmed that the generated electric fields align with the Lorentz equation. The effect significantly and safely modulated human peripheral nerves and deep brain regions of non-human primates.Significance:This approach opens a new set of applications in which electric fields are generated at high spatiotemporal resolution within intact biological tissues or materials, thus circumventing the limitations of traditional electrode-based procedures.

Magnetic field induced dose effects in radiation therapy using MR-linacs

MR-guided radiotherapy (MRgRT) is one of the most significant advances in radiotherapy in recent years. The hybrid systems were designed to visualize patient anatomical and physiological changes during the course of radiotherapy, enabling more precise treatment. However, before MR-linacs reach their full potential in delivering safe and accurate treatments to patients, the radiotherapy team must understand how a magnetic field alters the dosimetric properties of the radiation beam and its potential impact on treatment quality and clinical outcomes. This review aims to provide an in-depth description of the magnetic field induced dose effects for the two widely available systems, the 0.35 T and the 1.5 T MR-linacs. In MR-linac treatments, the primary photon beam passes through MR components that never exist in conventional linacs, which alter both in-field and out-of-field doses. More importantly, the interplay between the always-on magnetic field and the secondary electrons is not negligible. This interplay affects dose deposition in the patient, resulting in reduced in-field skin dose due to purged-out contaminant electrons, shortened build-up distance and a shifted crossline profile owing to asymmetric dose kernel. Especially two effects, namely electron return effect (ERE) and electron stream effect (ESE), are not seen in conventional radiotherapy. This review also summarizes the clinical observations on the site-specific treatments influenced mostly by the magnetic field. In MR-linac treatment, the head and neck region is one of the most challenging sites as ERE occurs at low and high density tissue interfaces and around air cavities, generating hot and cold spots. In breast cancer treatment, consideration should be given to the increased in-field skin dose induced by ERE and the increased out-of-field dose caused by ESE for regions such as the ears, chin, and neck. In lung cancer treatments, tissue inhomogeneity combined with ERE will exacerbate target dose heterogeneity and increase or decrease interface dose. Lastly, treatment in the abdomen and pelvic region will be affected by the presence of gas pockets near the target. The review provides practical recommendations to mitigate these effects. This article is protected by copyright. All rights reserved.

Magnetic-field-induced simultaneous charge separation and oxygen transfer in photocatalytic oxygen activation for algae inactivation

Photocatalytic oxygen activation is an excellent strategy for algae control in water. However, the fast recombination of photogenerated charge and slow rate of oxygen transfer limit the reactive oxygen species generation efficiency for algae inactivation. Herein, to solve above issues, magnetic field was introduced to the BiO_2-x/Bi₃NbO₇ system to effectively covert oxygen into reactive radicals. The electrochemical experiment and DFT calculation results indicated the charge separation could be accelerated by the Lorentz force generated by the magnetic field, resulting in increase of electron concentration. Meanwhile, the value of volumetric gas-liquid mass transfer coefficient was increased by 59.79 % with magnetic field, thus more oxygen could be reduced to superoxide radical. Photocatalytic algae inactivation rate by BiO_2-x/Bi₃NbO₇ with magnetic field could be increased by 2.07 times than that without magnet filed. This work further extends the strategy of using magnetic field to simultaneously facilitate the charge separation and oxygen transfer rate.

Can MRI Be Used as a Sensor to Record Neural Activity?

Magnetic resonance provides exquisite anatomical images and functional MRI monitors physiological activity by recording blood oxygenation. This review attempts to answer the following question: Can MRI be used as a sensor to directly record neural behavior? It considers MRI sensing of electrical activity in the heart and in peripheral nerves before turning to the central topic: recording of brain activity. The primary hypothesis is that bioelectric current produced by a nerve or muscle creates a magnetic field that influences the magnetic resonance signal, although other mechanisms for detection are also considered. Recent studies have provided evidence that using MRI to sense neural activity is possible under ideal conditions. Whether it can be used routinely to provide functional information about brain processes in people remains an open question. The review concludes with a survey of artificial intelligence techniques that have been applied to functional MRI and may be appropriate for MRI sensing of neural activity.

Application of Electromagnetic Braking to Minimize a Surface Wave in a Continuous Caster

The turbulent flow in the mold region drastically influences the quality of steel produced during continuous casting. The flow itself can lead to surface defects or slag entrainment based on the formation. A high surface wave can lead to fluctuations and the instability compromises the quality of the steel produced, as well as entrain the slag. To regulate the flow, electromagnetic forces can be applied in the mold, dampening the local turbulent flow. As the electrically conductive molten steel interacts with the induced magnetic field, it reduces the velocity of the steel jet released from the ports of the submerged entry nozzle. Utilizing Star-CCM+, a simulation-based study is conducted modeling the impact of Electromagnetic braking (EMBr) on the flow formation and surface standing wave. Specifically, a parametric study is conducted investigating the impact of submergence entry nozzle (SEN) depth and mold width with applied EMBr. Per the simulation-based study conducted increasing the EMBr strength from 2975 G to 4350 G reduced the average surface wave height by 12.5% and volume of flux rate of decrease by 4.25%. Additionally, increasing the SEN depth from 110 mm to 350 mm increased the average wave height by 19% and volume of flux rate of decrease by 2.6%. Lastly, increasing the mold width from 1.067 m to 1.50 m increased average wave height by 8.71% and volume of flux rate of decrease by 0.9%.

A Lorentz Force EMAT Design with Racetrack Coil and Periodic Permanent Magnets for Selective Enhancement of Ultrasonic Lamb Wave Generation

This article proposes an electromagnetic acoustic transducer (EMAT) for selectively improving the purity and amplitude of ultrasonic Lamb waves in non-ferromagnetic plates. The developed EMAT consists of a racetrack coil and a group of periodic permanent magnets (PPMs). Two-dimensional finite element simulations and experiments are implemented to analyze the working mechanism and performance of the PPM EMAT. Thanks to the specific design, the eddy currents increase with increasing wire density and the directions of the magnetic fields and Lorentz forces alternate according to the polarities of the magnet units. Wires laid uniformly beneath the magnets, and the gaps between adjacent magnets generate tangential and normal Lorentz forces, resulting in-plane (IP) and out-of-plane (OP) displacements, respectively. The constructive interference occurs when the wavelength of the generated Lamb wave is twice the spacing of the magnets, leading to large amplitudes of the targeted ultrasonic Lamb waves. Therefore, the PPM EMAT is capable of generating pure symmetric or antisymmetric mode Lamb waves at respective frequencies. The results prove that the developed PPM EMAT can generate pure either S0 or A0 mode Lamb waves at respective frequencies. The increase in wire width and wire density further increases the signal amplitudes. Compared with the case of conventional meander-line-coil (MLC) EMAT, the amplitudes of the A0 and S0 mode Lamb waves of our PPM EMAT are increased to 880% and 328%, respectively.

Experimental Investigation on the Machinability Improvement in Magnetic-Field-Assisted Turning of Single-Crystal Copper

The single-point diamond-turning operation is a commonly used method for ultra-precision machining of various non-ferrous materials. In this paper, a magnetic field was introduced into a single-point diamond-turning system, and magnetic-field-assisted turning experiments were carried out. The results revealed that the magnetic field affects the metal-cutting process in the form of the cutting force, chip morphology, and surface quality. Compared with traditional turning, magnetic-field assisted turning increases the cutting force by 1.6 times, because of the additional induced Lorentz force, and reduces the cutting-force ratio and friction coefficient on the rake surface by 16%, with the improved tribological property of the tool/chip contact-interface. The chip morphology in the magnetic-field-assisted turning shows the smaller chip-compression ratio and the continuous side-morphology. With the magnetoplasticity effect of the metal material and the friction reduction, magnetic-field-assisted turning is helpful for improving metal machinability and achieving better surface-quality.

Analysis on matrix gradient coil modeling

OBJECTIVE

The current distribution of the matrix gradient coil can be optimized via matrix gradient coil modeling to reduce the Lorentz force on individual coil elements. Two different modeling approaches are adopted, and their respective characteristics are summarized.

METHODS

The magnetic field at each coil element is calculated. Then, the Lorentz force, torque, and deformation of the energized coil element in the magnetic field are derived. Two modeling approaches for matrix gradient coil, namely, optimizing coil element current (OCEC) modeling and optimizing coil element Lorentz force (OCEF) modeling, are proposed to reduce the Lorentz force on individual coil elements. The characteristics of different modeling approaches are compared by analyzing the influence of the weighting factor on the performance of the coil system. The current, Lorentz force, torque, and deformation results calculated via different modeling approaches are also compared.

RESULTS

Coil element magnetic fields are much weaker than the main magnetic field, and their effect can be ignored. Matrix gradient coil modeling with different regularization terms can help to decrease the current and Lorentz force of coil elements. The performance of the coil system calculated via different modeling approaches is similar when suitable weighting factors are adopted. The two modeling approaches, OCEC and OCEF, can better reduce the maximum current and Lorentz force on individual coil elements compared with the traditional modeling approach.

CONCLUSIONS

Different modeling approaches can help to optimize the current distribution of coil elements and satisfy various requirements while maintaining the performance of the coil system.

Dynamic Analysis of Closed Die Electromagnetic Sheet Metal Forming to Predict Deformation and Failure of AA6061-T6 Alloy Using a Fully Coupled Finite Element Model

This research presents a fully coupled 3D numerical model to analyse the dynamics of high-speed electromagnetic forming process for aluminium alloy AA6061-T6. The effect of Lorentz force distribution, velocity and kinetic energy on deformation, the bounce back effect and failure of the sheet has been investigated. Experiments were performed for AA6061-T6 alloy using an 18.750 KJ electromagnetic forming machine for varying the sheet thickness (0.5 mm, 1.02 mm and 1.63 mm) compared with the simulation results. The results showed that increasing the sheet thickness increases the Lorentz force due to a higher induced current. The inertial forces were more pronounced in thicker sheets (1.63 mm) as compared to the thinner sheets (0.5 mm and 1.02 mm), resulting in a higher bounce back effect for the thicker sheet. The numerical model accurately predicted the sheet failure for the 0.5-mm sheet, as also observed from the experimentation. The sheet deformation from simulations was found to be in good agreement with the experimental results.

Highly Oriented Direct-Spun Carbon Nanotube Textiles Aligned by In Situ Radio-Frequency Fields

Carbon nanotubes (CNTs) individually exhibit exceptional physical properties, surpassing state-of-the-art bulk materials, but are used commercially primarily as additives rather than as a standalone macroscopic product. This limited use of bulk CNT materials results from the inability to harness the superb nanoscale properties of individual CNTs into macroscopic materials. CNT alignment within a textile has been proven as a critical contributor to narrow this gap. Here, we report the development of an altered direct CNT spinning method based on the floating catalyst chemical vapor deposition process, which directly interacts with the self-assembly of the CNT bundles in the gas phase. The setup is designed to apply an AC electric field to continuously align the CNTs in situ during the formation of CNT bundles and subsequent aerogel. A mesoscale CNT model developed to simulate the alignment process has shed light on the need to employ AC rather than DC fields based on a CNT stiffening effect (z-pinch) induced by a Lorentz force. The AC-aligned synthesis enables a means to control CNT bundle diameters, which broadened from 16 to 25 nm. The resulting bulk CNT textiles demonstrated an increase in the specific electrical and tensile properties (up to 90 and 460%, respectively) without modifying the quantity or quality of the CNTs, as verified by thermogravimetric analysis and Raman spectroscopy, respectively. The enhanced properties were correlated to the degree of CNT alignment within the textile as quantified by small-angle X-ray scattering and scanning electron microscopy image analysis. Clear alignment (orientational order parameter = 0.5) was achieved relative to the pristine material (orientational order parameter = 0.19) at applied field intensities in the range of 0.5-1 kV cm^-1 at a frequency of 13.56 MHz.

Key Role of Lorentz Excitation in the Electromagnetic-Enhanced Hydrogen Evolution Reaction

Alternating magnetic fields (AMFs) are recently demonstrated as a promising strategy to promote the electrochemical catalytic reactions. However, the underlying mechanisms are still an open question. In this work, we systematically investigated the influence of AMFs on the hydrogen evolution reaction (HER) by using a Fe-Co-Ni-P-B magnetic catalyst. The HER catalytic efficiency is boosted significantly by AMFs, with 27% increase in current density at 20 mT. This is attributed to the enhancement of charge-transfer efficiency by Lorentz interaction with a minor contribution from the heating effect. The high magnetic permeability and skin effect of electromagnetic eddy current for the Fe-Co-Ni-P-B electrode can magnify the Lorentz effect. These findings clarify the mechanism of AMF-enhanced HER catalytic activities and open a door for designing a high-efficiency electrocatalysis system.

Heat-Mitigated Design and Lorentz Force-Based Steering of an MRI-Driven Microcatheter toward Minimally Invasive Surgery

Catheters integrated with microcoils for electromagnetic steering under the high, uniform magnetic field within magnetic resonance (MR) scanners (3-7 Tesla) have enabled an alternative approach for active catheter operations. Achieving larger ranges of tip motion for Lorentz force-based steering have previously been dependent on using high power coupled with active cooling, bulkier catheter designs, or introducing additional microcoil sets along the catheter. This work proposes an alternative approach using a heat-mitigated design and actuation strategy for a magnetic resonance imaging (MRI)-driven microcatheter. A quad-configuration microcoil (QCM) design is introduced, allowing miniaturization of existing MRI-driven, Lorentz force-based catheters down to 1-mm diameters with minimal power consumption (0.44 W). Heating concerns are experimentally validated using noninvasive MRI thermometry. The Cosserat model is implemented within an MR scanner and results demonstrate a desired tip range up to 110° with 4° error. The QCM is used to validate the proposed model and power-optimized steering algorithm using an MRI-compatible neurovascular phantom and ex vivo kidney tissue. The power-optimized tip orientation controller conserves as much as 25% power regardless of the catheter's initial orientation. These results demonstrate the implementation of an MRI-driven, electromagnetic catheter steering platform for minimally invasive surgical applications without the need for camera feedback or manual advancement via guidewires. The incorporation of such system in clinics using the proposed design and actuation strategy can further improve the safety and reliability of future MRI-driven active catheter operations.

Persistent horizontal and vertical, MR-induced nystagmus in resting state Human Connectome Project data

OBJECTIVE

Strong magnetic fields from magnetic resonance (MR) scanners induce a Lorentz force that contributes to vertigo and persistent nystagmus. Prior studies have reported a predominantly horizontal direction for healthy subjects in a 7 Tesla (T) MR scanner, with slow phase velocity (SPV) dependent on head orientation. Less is known about vestibular signal behavior for subjects in a weaker, 3T magnetic field, the standard strength used in the Human Connectome Project (HCP). The purpose of this study is to characterize the form and magnitude of nystagmus induced at 3T.

METHODS

Forty-two subjects were studied after being introduced head-first, supine into a Siemens Prisma 3T scanner. Eye movements were recorded in four separate acquisitions over 20 minutes. A biometric eye model was fitted to the recordings to derive rotational eye position and then SPV. An anatomical template of the semi-circular canals was fitted to the T2 anatomical image from each subject, and used to derive the angle of the B₀ magnetic field with respect to the vestibular apparatus.

RESULTS

Recordings from 37 subjects yielded valid measures of eye movements. The population-mean SPV ± SD for the horizontal component was -1.38 ± 1.27 deg/sec, and vertical component was -0.93 ± 1.44 deg/sec, corresponding to drift movement in the rightward and downward direction. Although there was substantial inter-subject variability, persistent nystagmus was present in half of subjects with no significant adaptation over the 20 minute scanning period. The amplitude of vertical drift was correlated with the roll angle of the vestibular system, with a non-zero vertical SPV present at a 0 degree roll.

INTERPRETATION

Non-habituating vestibular signals of varying amplitude are present in resting state data collected at 3T.

Numerical and Experimental Study on the Direct Chill Casting of Large-Scale AA2219 Billets via Annular Coupled Electromagnetic Field

The internal coupled electromagnetic melt treatment (ICEMT) method is firstly proposed to produce high-quality and large-sized aluminum alloy billets. A three-dimensional model was established to describe the ICEMT process of direct chill casting (DC casting). The effect of ICEMT on the fluid flow patterns and temperature field in the DC casting of ϕ880 mm AA2219 billets is numerically analyzed. Moreover, the mechanisms of the ICEMT process on grain refinement and macrosegregation were discussed. The calculated results indicate that the electromagnetic field appears to be coupled circinate at the cross section of the melt, the fluid flow becomes unstable accompanied by the bias flow, and the temperature profiles are significantly more uniform. An experimental verification was conducted and the results prove that compared with traditional direct chill casting, the microstructures of the AA2219 large-scale billet under the ICEMT process are uniform and fine.

The dose response of PTW microDiamond and microSilicon in transverse magnetic field under small field conditions

The aim of the present work is to investigate the behavior of two diode-type detectors (PTW microDiamond 60019 and PTW microSilicon 60023) in transverse magnetic field under small field conditions. A formalism based on TRS 483 has been proposed serving as the framework for the application of these high-resolution detectors under these conditions. Measurements were performed at the National Metrology Institute of Germany (PTB, Braunschweig) using a research clinical linear accelerator facility. Quadratic fields corresponding to equivalent square field sizesSbetween 0.63 and 4.27 cm at the depth of measurement were used. The magnetic field strength was varied up to 1.4 T. Experimental results have been complemented with Monte Carlo simulations up to 1.5 T. Detailed simulations were performed to quantify the small field perturbation effects and the influence of detector components on the dose response. The does response of both detectors decreases by up to 10% at 1.5 T in the largest field size investigated. InS = 0.63 cm, this reduction at 1.5 T is only about half of that observed in field sizesS > 2 cm for both detectors. The results of the Monte Carlo simulations show agreement better than 1% for all investigated conditions. Due to normalization at the machine specific reference field, the resulting small field output correction factors for both detectors in magnetic fieldkQclin,QmsrBare smaller than those in the magnetic field-free case, where correction up to 6.2% at 1.5 T is required for the microSilicon in the smallest field size investigated. The volume-averaging effect of both detectors was shown to be nearly independent of the magnetic field. The influence of the enhanced-density components within the detectors has been identified as the major contributors to their behaviors in magnetic field. Nevertheless, the effect becomes weaker with decreasing field size that may be partially attributed to the deficiency of low energy secondary electrons originated from distant locations in small fields.

The role of the construction and sensitive volume of compact ionization chambers on the magnetic field-dependent dose response

PURPOSE

The magnetic-field correction factors k B , Q of compact air-filled ionization chambers have been investigated experimentally and using Monte Carlo simulations up to 1.5 T. The role of the nonsensitive region within the air cavity and influence of the chamber construction on its dose response have been elucidated.

MATERIALS AND METHODS

The PTW Semiflex 3D 31021, PinPoint 3D 31022, and Sun Nuclear Cooperation SNC125c chambers were studied. The k B , Q factors were measured at the experimental facility of the German National Metrology Institute (PTB) up to 1.4 T using a 6 MV photon beam. The chambers were positioned with the chamber axis perpendicular to the beam axis (radial); and parallel to the beam axis (axial). In both cases, the magnetic field was directed perpendicular to both the beam axis and chamber axis. Additionally, the sensitive volumes of these chambers have been experimentally determined using a focused proton microbeam and finite element method. Beside the simulations of k B , Q factors, detailed Monte Carlo technique has been applied to analyse the secondary electron fluence within the air cavity, that is, the number of secondary electrons and the average path length as a function of the magnetic field strength.

RESULTS

A nonsensitive volume within the air cavity adjacent to the chamber stem for the PTW chambers has been identified from the microbeam measurements and FEM calculations. The dose response of the three investigated ionization chambers does not deviate by more than 4% from the field-free case within the range of magnetic fields studied in this work for both the radial and axial orientations. The simulated k B , Q for the fully guarded PTW chambers deviate by up to 6% if their sensitive volumes are not correctly considered during the simulations. After the implementation of the sensitive volume derived from the microbeam measurements, an agreement of better than 1% between the experimental and Monte Carlo k B , Q factors for all three chambers can be achieved. Detailed analysis reveals that the stem of the PTW chambers could give rise to a shielding effect reducing the number of secondary electrons entering the air cavity in the presence of magnetic field. However, the magnetic field dependence of their path length within the air cavity is shown to be weaker than for the SNC125c chamber, where the length of the air cavity is larger than its diameter. For this chamber it is shown that the number of electrons and their path lengths in the cavity depend stronger on the magnetic field.

DISCUSSION AND CONCLUSION

For clinical measurements up to 1.5 T, the required k B , Q corrections of the three chambers could be kept within 3% in both the investigated chamber orientations. The results reiterate the importance of considering the sensitive volume of fully guarded chambers, even for the investigated compact chambers, in the Monte Carlo simulations of chamber response in magnetic field. The resulting magnetic field-dependent dose response has been demonstrated to depend on the chamber construction, such as the ratio between length and the diameter of the air cavity as well as the design of the chamber stem.

Rapidly deployable and morphable 3D mesostructures with applications in multimodal biomedical devices

Structures that significantly and rapidly change their shapes and sizes upon external stimuli have widespread applications in a diversity of areas. The ability to miniaturize these deployable and morphable structures is essential for applications in fields that require high-spatial resolution or minimal invasiveness, such as biomechanics sensing, surgery, and biopsy. Despite intensive studies on the actuation mechanisms and material/structure strategies, it remains challenging to realize deployable and morphable structures in high-performance inorganic materials at small scales (e.g., several millimeters, comparable to the feature size of many biological tissues). The difficulty in integrating actuation materials increases as the size scales down, and many types of actuation forces become too small compared to the structure rigidity at millimeter scales. Here, we present schemes of electromagnetic actuation and design strategies to overcome this challenge, by exploiting the mechanics-guided three-dimensional (3D) assembly to enable integration of current-carrying metallic or magnetic films into millimeter-scale structures that generate controlled Lorentz forces or magnetic forces under an external magnetic field. Tailored designs guided by quantitative modeling and developed scaling laws allow formation of low-rigidity 3D architectures that deform significantly, reversibly, and rapidly by remotely controlled electromagnetic actuation. Reconfigurable mesostructures with multiple stable states can be also achieved, in which distinct 3D configurations are maintained after removal of the magnetic field. Demonstration of a functional device that combines the deep and shallow sensing for simultaneous measurements of thermal conductivities in bilayer films suggests the promising potential of the proposed strategy toward multimodal sensing of biomedical signals.

Effects of a Constant Magnetic Field on the Electrochemical Reactions of Quercetin

The paper presents a study of the effect of a constant magnetic field (CMF) on the basic processes of quercetin electrochemical reactions. According to the observation made in previous studies, the presence of a double bond in the C-ring of quercetin enhances the antioxidant properties of that compound, whereas the presence of -OH groups also affects the antioxidant properties. Using cyclic voltammetry it was found that the constant magnetic field improves the efficiency of quercetin electrooxidation, especially of the third stage of the process, i. e. the stage in which the oxidation of the OH groups in the A-ring is the most difficult. The use of HPLC confirmed the electrochemical measurements and the results of cyclic voltammetry studies. The beneficial effect of the magnetic field on the efficiency of quercetin oxidation was confirmed by the results of impedance spectroscopy measurements.

The Lorentz force on ions in membrane channels of neurons as a mechanism for transcranial static magnetic stimulation

Transcranial static magnetic stimulation is a novel noninvasive method of reduction of the cortical excitability in certain neurological diseases that makes use of static magnetic fields generated by permanent magnets. By contrast, ordinary transcranial magnetic stimulation makes use of pulsed magnetic fields generated by strong currents. Whereas the physical principle underlying ordinary transcranial magnetic stimulation is well known, that is, the Faraday´s law, the physical mechanism that explains the interaction between neurons and static magnetic fields in transcranial static magnetic stimulation remains unclear. In the present work, it is discussed the possibility that this mechanism might be the Lorentz force exerted on the ions flowing along the membrane channels of neurons. The overall effect of the static magnetic field would be to introduce an additional friction between the ions and the walls of the membrane channels, thus reducing its conductance. Calculations performed by using a Hodgkin-Huxley model demonstrate that even a slight reduction of the conductance of the membrane channels can lead to the suppression of the action potential, thus inhibiting neuronal activity.

Electrochemical Characteristics and Transport Properties of V(II)/V(III) Redox Couple in a Deep Eutectic Solvent: Magnetic Field Effect

Compared with conventional aqueous electrolytes, deep eutectic solvent (DES) has a wider electrochemical stability window, simple preparation, potential biodegradability, and lower cost, leading to its utilization as electrolyte for non-aqueous redox flow batteries (RFB). However, the large viscosity and inferior transport properties hinder the wide spread of DES electrolyte. To circumvent these issues, various additives as well as external fields can be applied separately or synergistically. This work reports a study on the inclusion of a DC magnetic field to the glycol-based DES electrolyte of a RFB. The effects of magnetic field on the physical and electrochemical characteristics of the electrolyte and the active redox couple on mass transfer are studied by cyclic voltammetry and electrochemical impedance spectroscopy. The experimental results show that the viscosity of the vanadium DES electrolyte decreases and the conductivity increases after adding a magnetic field. With the intensity of the added magnetic field increases, the oxidation and reduction peak current densities of the vanadium DES electrolyte keep increasing. Under the magnetic field intensity of 605 mT, the oxidation peak current density and the reduction peak current density increases 41.56 and 30.74%, respectively, compared with those of no added magnetic field. The ohmic resistance and electrochemical reaction resistance of the vanadium DES electrolyte are reduced when adding the magnetic field, reaching to 40.55 and 43.28%, respectively, with a magnetic field intensity of 605 mT. This study shows an effective yet simple way to improve the physical and electrochemical properties of DES electrolyte, which owns the potential to be widely applied in non-aqueous redox flow batteries.

In-situ MRI velocimetry of the magnetohydrodynamic effect in electrochemical cells

Electrochemical reactions have become increasingly important in a large number of processes and applications. The use of NMR (Nuclear Magnetic Resonance) techniques to follow in situ electrochemistry processes has been gaining increasing attention from the scientific community because they allow the identification and quantification of the products and reagents, whereas electrochemistry measurements alone are not able to do so. However, when an electrochemical reaction is performed in situ the reaction rate can be increased by action of the Lorentz force, which is equal to the cross product between the current density and the magnetic field applied. This phenomenon is called the magnetohydrodynamic (MHD) effect. Although this process is beneficial because it accelerates the reaction, it needs to be well understood and taken into account during the in situ electrochemical measurements. The MHD effect is based on increased mass transfer, which is shown by in situ MRI velocimetry here. Images had to be acquired in a rapid manner since current was not pulsed. Significant velocities in a plane parallel to the electrodes alongside with complex flow patterns were detected.

Suppressing Photoinduced Charge Recombination via the Lorentz Force in a Photocatalytic System

Suppressing the recombination of photogenerated charges is one of the most important routes for enhancing the catalytic performance of semiconductor photocatalysts. In addition to the built-in field produced by semiconductor heterostructures and the photo-electrocatalysis realized by applying an external electrical potential to photocatalysts assembled on electrodes, other strategies are waiting to be scientifically explored and understood. In this work, a Lorentz force-assisted charge carrier separation enhancement strategy is reported to improve the photocatalytic efficiency by applying a magnetic field to a photocatalytic system. The photocatalytic efficiency can be improved by 26% just by placing a permanent magnet beneath the normal photocatalytic system without any additional power supply. The mechanism by which the Lorentz force acts oppositely on the photogenerated electrons and holes is introduced, resulting in the suppression of the photoinduced charge recombination. This work provides insights into the specific role of the Lorentz force in suppressing the recombination of electron-hole pairs in their initial photogenerated states. This suppression would increase the population of charge carriers that would subsequently be transported in the semiconductor. It is believed that this strategy based on magnetic effects will initiate a new way of thinking about photoinduced charge separation.

A New Theoretical Approach of Wall Transpiration in the Cavity Flow of the Ferrofluids

An idea of permeable (suction/injection) chamber is proposed in the current work to control the secondary vortices appearing in the well-known lid-driven cavity flow by means of the water based ferrofluids. The Rosensweig model is conveniently adopted for the mathematical analysis of the physical problem. The governing equation of model is first transformed into the vorticity transport equation. A special finite difference method in association with the successive over-relaxation method (SOR) is then employed to numerically simulate the flow behavior. The effects of intensity of magnetic source (controlled by the Stuart number), aspect ratio of the cavity, rate of permeability (i.e., αp=V0U), ratio of speed of suction/injection V0 to the sliding-speed U of the upper wall of a cavity, and Reynolds number on the ferrofluid in the cavity are fully examined. It is found that the secondary vortices residing on the lower wall of the cavity are dissolved by the implementation of the suction/injection chamber. Their character is dependent on the rate of permeability. The intensity of magnetic source affects the system in such a way to alter the flow and to transport the fluid away from the magnetic source location. It also reduces the loading effects on the walls of the cavity. If the depth of cavity (or the aspect ratio) is increased, the secondary vortices join together to form a single secondary vortex. The number of secondary vortices is shown to increase if the Reynolds number is increased for both the clear fluid as well as the ferrofluids. The suction and injection create resistance in settlement of solid ferroparticles on the bottom. The results obtained are validated with the existing data in the literature and satisfactory agreement is observed. The presented problem may find applications in biomedical, pharmaceutical, and engineering industries.

A decade of magnetic vestibular stimulation: from serendipity to physics to the clinic

For many years, people working near strong static magnetic fields of magnetic resonance imaging (MRI) machines have reported dizziness and sensations of vertigo. The discovery a decade ago that a sustained nystagmus can be observed in all humans with an intact labyrinth inside MRI machines led to a possible mechanism: a Lorentz force occurring in the labyrinth from the interactions of normal inner ear ionic currents and the strong static magnetic fields of the MRI machine. Inside an MRI, the Lorentz force acts to induce a constant deflection of the semicircular canal cupula of the superior and lateral semicircular canals. This inner ear stimulation creates a sensation of rotation, and a constant horizontal/torsional nystagmus that can only be observed when visual fixation is removed. Over time, the brain adapts to both the perception of rotation and the nystagmus, with the perception usually diminishing over a few minutes, and the nystagmus persisting at a reduced level for hours. This observation has led to discoveries about how the central vestibular mechanisms adapt to a constant vestibular asymmetry and is a useful model of set-point adaptation or how homeostasis is maintained in response to changes in the internal milieu or the external environment. We review what is known about the effects of stimulation of the vestibular system with high-strength magnetic fields and how the understanding of the mechanism has been refined since it was first proposed. We suggest future ways that magnetic vestibular stimulation might be used to understand vestibular disease and how it might be treated.

Dual Resonator MEMS Magnetic Field Gradiometer

Accurate knowledge of the spatial magnetic field distribution is necessary when measuring field gradients. Therefore, a MEMS magnetic field gradiometer is reported, consisting of two identical, but independent laterally oscillating masses on a single chip. The sensor is actuated by Lorentz force and read out by modulation of the light flux passing through stationary and moving arrays of the chip. This optical readout decouples the transducer from the electronic components. Both phase and intensity are recorded which reveals information about the uniformity of the magnetic field. The magnetic flux density is measured simultaneously at two points in space and the field gradient is evaluated locally. The sensor was characterised at ambient pressure by performing frequency and magnitude response measurements with coil and various different permanent magnet arrangements, resulting in a responsivity of 35.67 V/T and detection limit of 3.07 µT/ Hz (@ 83 Hz ENBW). The sensor is compact, offers a large dynamic measurement range and can be of low-cost by using conventional MEMS batch fabrication technology.

A Miniature Resonant and Torsional Magnetometer Based on Lorentz Force

A microelectromechanical system (MEMS) torsional resonant magnetometer based on Lorentz force was investigated, consisting of torsional structures, torsional beams, metal plates, a coil, and a glass substrate. The Lorentz force, introduced by the interaction between the current in the MEMS coil and an external horizontal magnetic field, leads to displacement of the torsional structure. The strength of the magnetic field is proportional to this displacement, and can be detected with two sensing capacitors fabricated on the torsion structure and the substrate. To improve sensor sensitivity, a folded torsional beam and a double-layer excitation coil were introduced. The fabrication processes included lift-off, anodic bonding, chemical mechanical planarization, silicon nitride (SiNx) deposition, plasma-enhanced chemical vapor deposition, and inductively coupled plasma release. The prototype of the magnetometer was finished and packaged. The sensor performance, including its sensitivity and repeatability, was tested in a low-pressure environment. Additionally, the influences of structural parameters were analyzed, including the resistance of the excitation coil, the initial value of the capacitors, the elastic coefficient of the torsional beam, and the number of layers in the excitation coil. The test results demonstrated that this sensor could meet the requirements for attitude determination systems in low earth orbit satellites.

Lorentz Nanoplasmonics for Nonlinear Generation

While past works have suggested that the Lorentz magnetic contribution to second harmonic generation from metal nanostructures is negligible as compared to other terms, here we demonstrate a dominant Lorentz contribution from T-shaped apertures in a gold film. The apertures are designed to have overlapping magnetic and electric near-field intensities at the plasmonic resonance. This gives 65% greater nonlinear generation from the Lorentz term than the sum of the other two terms. We demonstrate this effect experimentally by milling of nanoapertures of different size and orientation in a metal film and measuring their second harmonic generation. Good agreement is seen between the experiments and comprehensive calculations. In the development of highly efficient nonlinear metasurfaces, careful optimization of the Lorentz contribution should be considered in addition to all other contributions. Following the approach of this work, the Lorentz contribution may also be optimized for THz generation.

Long-Range Self-Assembly via the Mutual Lorentz Force of Plasmon Radiation

Long-range interactions often proceed as a sequence of hopping through intermediate, statistically favored events. Here, we demonstrate predictable mechanical dynamics of particles that arise from the Lorentz force between plasmons. Even if the radiation is weak, the nonconservative Lorentz force produces stable locations perpendicular to the plasmon oscillation; over time, distinct patterns emerge. Experimentally, linearly polarized light illumination leads to the formation of 80 nm diameter Au nanoparticle chains, perpendicularly aligned, with lengths that are orders of magnitude greater than their plasmon near-field interaction. There is a critical intensity threshold and optimal concentration for observing self-assembly.

A multi-objective structural optimization of an omnidirectional electromagnetic acoustic transducer

In this paper an axisymmetric model of an omnidirectional electromagnetic acoustic transducer (EMAT) used to generate Lamb waves in conductive plates is introduced. Based on the EMAT model, the structural parameters of the permanent magnet were used as the design variables while other parameters were fixed. The goal of the optimization was to strengthen the generation of the A0 mode and suppress the generation of the S0 mode. The amplitudes of the displacement components at the observation point of the plate were used for calculation of the objective functions. Three approaches to obtain the amplitudes were discussed. The first approach was solving the peak values of the envelopes of the time waveforms from the time domain simulations. The second approach also involved calculation of the peaks, but the waveforms were from frequency domain model combined with the forward and inverse Fourier transforms. The third approach involved a single frequency in the frequency domain model. Single and multi-objective optimizations were attempted, implemented with the genetic algorithms. In the single objective optimizations, the goal was decreasing the ratio of the amplitudes of the S0 and A0 modes, while in the multi-objective optimizations, an extra goal was strengthening the A0 mode directly. The Pareto front from the multi-objective optimizations was compared with the estimation from the data on the discrete grid of the design variables. From the analysis of the results, it could be concluded that for a linearized steel plate with a thickness of 10mm and testing frequency of 50kHz, the point with minimum S0/A0 could be selected, thus the multi-objective optimization effectively degenerated to the single objective optimization. While for an aluminum plate with a thickness of 3mm and frequency of 150kHz, without further information it would be difficult to select one particular solution from the Pareto front.

Magnetic Field-Assisted Perovskite Film Preparation for Enhanced Performance of Solar Cells

Perovskite solar cells (PSCs) are promising low-cost photovoltaic technologies with high power conversion efficiency (PCE). The crystalline quality of perovskite materials is crucial to the photovoltaic performance of the PSCs. Herein, a simple approach is introduced to prepare high-quality CH₃NH₃PbI₃ perovskite films with larger crystalline grains and longer carriers lifetime by using magnetic field to control the nucleation and crystal growth. The fabricated planar CH₃NH₃PbI₃ solar cells have an average PCE of 17.84% and the highest PCE of 18.56% using an optimized magnetic field at 80 mT. In contrast, the PSCs fabricated without the magnetic field give an average PCE of 15.52% and the highest PCE of 16.72%. The magnetic field action produces an ordered arrangement of the perovskite ions, improving the crystallinity of the perovskite films and resulting in a higher PCE.

A Simple Drain Current Model for MOS Transistors with the Lorentz Force Effect

A novel concept of drain current modelling in rectangular normal MOS transistors with the Lorentz force has been proposed for the first time. The single-drain MOS transistor is qualified as a magnetic sensor. To create the Lorentz force, a DC loop current is applied through an on-chip metal loop around the device, and the relation between the applied loop current and the created magnetic field is assumed to be linear in nature. The drain current of the MOS transistor is reduced with the applied Lorentz force from both directions. This change in the drain current is ascribed to a change in mobility in the strong inversion region, and a change in mobility of around 4.45% is observed. To model this change, a set of novel drain current equations, under the Lorentz force, for the strong inversion region has been proposed. A satisfactory agreement of an average error of less than 2% between the measured and the calculated drain currents under the magnetic field created by an on-chip metal loop is achieved.

A Study on the Influence of the Nozzle Lead Angle on the Performance of Liquid Metal Electromagnetic Micro-Jetting

To improve the jetting performance of liquid metals, an electromagnetic micro-jetting (EMJ) valve that realizes drop-on-demand (DOD) jetting while not involving any valve core or moving parts was designed. The influence of the lead angle of the nozzle on the jetting of liquid metal gallium (Ga) was investigated. It was found that the Lorentz force component parallel to the nozzle that jets the electrified liquid Ga is always larger than its internal friction; thus, jet can be generated with any lead angle but with different kinetic energies. Experimental results show that the mass of the jetting liquid, the jetting distance, the initial velocity of the jet, and the resulting kinetic energy of the jet increase first and then decrease. When the lead angle is 90°, the mass of the jetting liquid and the kinetic energy are at their maximum. When the angle is 80°, the initial velocity achieves its maximum, with a calculated value of 0.042 m/s. Moreover, very close and comparatively high kinetic energies are obtained at 80° and 90°, indicating that angles in between this range can produce a preferable performance. This work provides an important theoretical basis for the design of the EMJ valve, and may promote the development and application of micro electromagnetic jetting technology.

Drain Current Modulation of a Single Drain MOSFET by Lorentz Force for Magnetic Sensing Application

This paper reports a detailed analysis of the drain current modulation of a single-drain normal-gate n channel metal-oxide semiconductor field effect transistor (n-MOSFET) under an on-chip magnetic field. A single-drain n-MOSFET has been fabricated and placed in the center of a square-shaped metal loop which generates the on-chip magnetic field. The proposed device designed is much smaller in size with respect to the metal loop, which ensures that the generated magnetic field is approximately uniform. The change of drain current and change of bulk current per micron device width has been measured. The result shows that the difference drain current is about 145 µA for the maximum applied magnetic field. Such changes occur from the applied Lorentz force to push out the carriers from the channel. Based on the drain current difference, the change in effective mobility has been detected up to 4.227%. Furthermore, a detailed investigation reveals that the device behavior is quite different in subthreshold and saturation region. A change of 50.24 µA bulk current has also been measured. Finally, the device has been verified for use as a magnetic sensor with sensitivity 4.084% (29.6 T⁻¹), which is very effective as compared to other previously reported works for a single device.

Recent Advances of MEMS Resonators for Lorentz Force Based Magnetic Field Sensors: Design, Applications and Challenges

Microelectromechanical systems (MEMS) resonators have allowed the development of magnetic field sensors with potential applications such as biomedicine, automotive industry, navigation systems, space satellites, telecommunications and non-destructive testing. We present a review of recent magnetic field sensors based on MEMS resonators, which operate with Lorentz force. These sensors have a compact structure, wide measurement range, low energy consumption, high sensitivity and suitable performance. The design methodology, simulation tools, damping sources, sensing techniques and future applications of magnetic field sensors are discussed. The design process is fundamental in achieving correct selection of the operation principle, sensing technique, materials, fabrication process and readout systems of the sensors. In addition, the description of the main sensing systems and challenges of the MEMS sensors are discussed. To develop the best devices, researches of their mechanical reliability, vacuum packaging, design optimization and temperature compensation circuits are needed. Future applications will require multifunctional sensors for monitoring several physical parameters (e.g., magnetic field, acceleration, angular ratio, humidity, temperature and gases).

Metrology of electromagnetic static actuation of MEMS microbridge using atomic force microscopy

The objective of this paper is to describe application of atomic force microscopy (AFM) for characterization and calibration of static deflection of electromagnetically and/or thermally actuated micro-electromechanical (MEMS) bridge. The investigated MEMS structure is formed by a silicon nitride bridge and a thin film metal path enabling electromagnetic and/or thermal deflection actuation. We present how static microbridge deflection can be measured using contact mode AFM technology with resolution of 0.05nm in the range of up to tens of nm. We also analyze, for very small structure deflections and under defined and controlled load force varied in the range up to ca. 32nN, properties of thermal and electromagnetical microbridge deflection actuation schemes.

Optical Characterization of Lorentz Force Based CMOS-MEMS Magnetic Field Sensor

Magnetic field sensors are becoming an essential part of everyday life due to the improvements in their sensitivities and resolutions, while at the same time they have become compact, smaller in size and economical. In the work presented herein a Lorentz force based CMOS-MEMS magnetic field sensor is designed, fabricated and optically characterized. The sensor is fabricated by using CMOS thin layers and dry post micromachining is used to release the device structure and finally the sensor chip is packaged in DIP. The sensor consists of a shuttle which is designed to resonate in the lateral direction (first mode of resonance). In the presence of an external magnetic field, the Lorentz force actuates the shuttle in the lateral direction and the amplitude of resonance is measured using an optical method. The differential change in the amplitude of the resonating shuttle shows the strength of the external magnetic field. The resonance frequency of the shuttle is determined to be 8164 Hz experimentally and from the resonance curve, the quality factor and damping ratio are obtained. In an open environment, the quality factor and damping ratio are found to be 51.34 and 0.00973 respectively. The sensitivity of the sensor is determined in static mode to be 0.034 µm/mT when a current of 10 mA passes through the shuttle, while it is found to be higher at resonance with a value of 1.35 µm/mT at 8 mA current. Finally, the resolution of the sensor is found to be 370.37 µT.

Resonant Magnetic Field Sensors Based On MEMS Technology

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration.