Coil Size Research Articles

Simulation of a Microsolenoid for the Detection of Magnetical Captured Beads

Low-cost, fast and accurate antibody detection is important for viral infection testing, especially for in cases of epidemics or pandemics. Currently, most rapid antibody detection methods are based on lateral flow immunoassay tests. [1] Beads offer a convenient way to capture and concentrate antigens, antibodies, and other biological molecules but determining the concentration or number can be a challenge, in particular at lower concentration levels. What we would like to achieve is the ability to detect much lower concentration levels, and in principle count individual molecules or a bound complex labelled with the magnetic bead using a micro-solenoid.In this paper, a three-dimensional, hollow channel, micro-solenoid is investigated to improve sensitivity, with antibody testing using magnetic microbeads bound to the target antigen. Previous work has shown the use of magnetic microbeads for microfluidic devices [2]. The micro-solenoid is simulated using COMSOL multiphysics to test various geometric parameters such as bead size, coil size, and bead velocity for the goal of detecting and counting antibodies bound to the beads.A time dependent model was constructed in COMSOL using the magnetic fields and moving mesh modules. In order to simplify the simulation, a 2D axisymmetric model was used and the model was first solved using a stationary step. The bead is represented by a short cylinder, and the solenoid as a uniform diameter annular cylinder, 390 um in length. The coil was simulated through the coil interface under the magnetic fields module allowing it to be represented as single uniform object with variable number of turns, conductivity, and cross-sectional area.For several sets of constant bead size, coil size, and bead magnetization, the maximum voltage reached was found to be a linear function with respect to velocity. In terms of coil radius, the simulated voltage response decreased quadratically with increasing radius however this was only significant when the bead size was appreciable to the coil size for simulations featuring coil radii of 15, 25, 35, and 50 um with 2, 5, 10, and 12.5 um radii beads. The data is presented in figure 1A and 1B. The results for 10 and 12.5 um radius bead are the only ones with appreciable curvature. The simulated voltage response increased quadratically with increasing bead size and the curvature of the underlying quadratic fit increased with decreased coil radius. Future avenues of study include 3 dimensional designs and simulations and fabrication using microfabricated coils.[1] D. A. Mistry, J. Y. Wang, M.-E. Moeser, T. Starkey, and L. Y. W. Lee, “A systematic review of the sensitivity and specificity of lateral flow devices in the detection of SARS-CoV-2.,” BMC Infect. Dis., vol. 21, no. 1, p. 828, Aug. 2021, doi: 10.1186/s12879-021-06528-3.[2] Kyu Sung Kim and Je-Kyun Park, “Magnetic force-based immunoassay using superparamagnetic nanoparticles in microfluidic channel,” in The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS ’05., Jun. 2005, vol. 1, pp. 81-84 Vol. 1. doi: 10.1109/SENSOR.2005.1496364. Figure 1

Environmental vibration energy collection technology based on piezoelectric and electromagnetic model

In this paper, the vibration model of the piezoelectric cantilever, the piezoelectric and electromagnetic output model are established. The simulation analysis of the cantilever vibration is performed using Comsol Multiphysics software. The effects of structural parameters, including cantilever length, cantilever thickness, piezoelectric layer length, piezoelectric layer thickness, coil size and position, on the resonance frequency and output voltage were analyzed. A cantilever vibration energy collection device is designed. The feasibility and accuracy of theoretical analysis were verified through the experiment, and the resonance frequency and the output voltage of the experiment basically agree with the theoretical calculation value.

Wireless charging for cardiac pacemakers based on class‐D power amplifier and a series–parallel spider‐web coil

AbstractBiomedical implants (BMIs) and biomedical sensors (BMSs) help to improve quality of life, detect diseases, provide monitoring of vital signs, and take over the role of malfunctioning organs. These implants and sensors require continuous battery power to work effectively, but the batteries used are restricted by their limited capacity and lifetime. This research reported here involved the design and implementation of a wireless charging system based on a series–parallel spider‐web coil (WPT‐SP‐SWC), specifically for cardiac pacemakers. The experimental design investigated several important parameters, including air gap, applied source voltage, coil size, and operating frequency. Performance metrics were evaluated in terms of output DC voltage, delivered output power, and power transfer efficiency. The target voltage was 5 V, which is adequate to charge a BMI such as a pacemaker, and three source voltages (5, 15, and 25 V) were tested. The design was examined at six operating frequencies, ranging from 1.78 MHz to 6.78 MHz. The most favorable results were achieved at 1.78 MHz. Power transfer efficiencies at a 10 mm air gap were 95.75% and 92.08% for applied voltages of 5 V and 15 V, respectively. The effectiveness of the proposed system was also validated by comparing the findings with previous articles.

Study on the Magnetic Properties of Metal Substrates at Low Temperature by Fabricated Compact SST

In recent years, a development of a high magnetic field magnet using a high temperature superconducting (HTS) wire has been advanced. On the other hand, we are planning to use the HTS wires for superconducting applications cooled by cryocooler. So, it is necessary to measure the temperature dependence of the magnetic properties of the metal substrates (Hastelloy, stainless steel and NiW) for HTS wire under conduction cooling conditions. We have been developing a single sheet tester (SST) that can evaluate the magnetic properties of electromagnetic steel sheets and other materials. However, since the size of an excitation coil in the conventional SST is large, it is difficult to install them in the conduction cooling system. In this study, we fabricated the compact SST and its measurement accuracy was compared with the conventional SST. The magnetic properties of metal substrates were measured at room temperature and liquid nitrogen temperature (77 K). As a result, although the measurement accuracy of the compact SST was slightly reduced by decreasing the coil size, we found that the error of the magnetic field homogeneity of the compact SST was within 2&#x0025; at the center region of the 5 mm length. The magnetic properties of Hastelloy and stainless steel were almost unchanged at both room temperature and liquid nitrogen temperature. However, the magnetic properties of the NiW substrate changed significantly at liquid nitrogen temperature. The <i>B</i>-<i>H</i> characteristics of the NiW substrate in the rolling and transverse directions were clearly different, and the iron loss increased significantly at liquid nitrogen temperature.

Integrated MEMS Toroidal Transformer With Ni-Zn Ferrite Core for Power Supply on Chip

A miniature integrable transformer is an obstacle to the miniaturization of packaged power supply on chip (PwrSoC). This letter introduces a through-silicon via (TSV) high-aspect-ratio toroidal transformer manufactured using microelectro-mechanical systems and electroplating. The primary coil and secondary coil of the transformer are interleaved on the toroidal core cavity, which is entirely wrapped in silicon, and a 1.2 mm high toroidal Ni-Zn ferrite core is formed. A 15:15 turn transformer is fabricated with a compact coil size of Φ4.1 × 2 mm with an aspect ratio (ratio of TSV depth to diameter) of 20. Measurements show that it has an inductance of 105 to 115 nH in a high frequency range of 1 to 80 MHz and a coupling coefficient of ∼0.7 in the range of 1 MHz to >15 MHz. Compared to that of the transformer without the Ni-Zn ferrite core, the coupling coefficient of the toroidal transformer increases by 40% with an inductance increase of 20%. At a frequency of 14 MHz, the transformer has a maximum quality factor of 16.7. The small size, IC compatible manufacturing process and excellent performance at high-frequency of the transformer proposed, meet the further integrated and miniaturized needs of PwrSoC.

Experimental Study on Profile Control of Polymer and Weak Gel Molecules in Porous Media.

Weak gel is a gel system formed by the mixing and crosslinking of a low-concentration polymer and a slow-release crosslinker. It can be used for profile control in deep reservoir, but its effect is greatly affected by mechanical shearing. Currently, the shearing effect on weak gel is mainly studied by way of mechanical stirring, while the effect of porous media shear on weak gel molecules and properties has been rarely discussed. In this paper, polymer solution, aluminum gel and phenolic gel were prepared. The molecular coil size, viscoelastic modulus and microscopic aggregation morphology in water solution of three systems before and after core shearing were investigated, and the injection performance of the three systems in cores with different permeabilities was tested by physical simulation experiments. The study results show that at equivalent permeability, the system with a larger equivalent sphere diameter of molecular coil is more seriously sheared and suffers greater viscosity loss. In the core with permeability of 1.0 D, polymer solution remains as the aggregation, while phenolic gel and aluminum gel cannot form network aggregations and they are inferior to polymer solution in migration capacity in the mid-deep part of the core. In the core with permeability of 1–5.8 D, the polymer solution remains as a Newtonian fluid, while phenolic gel and aluminum gel become purely viscous non-Newtonian fluids. The elastic modulus of aluminum gel and phenolic gel is four times more than that of a polymer. In the core with permeability higher than 8.5 D, aluminum gel and phenolic gel migrate with less effect by core shearing, and their profile control capacity in deep reservoir is higher than that of the polymer. In the core with permeability lower than 8.5 D, because the monomolecular activity of weak gels becomes poor, they migrate in porous media with more effect by core shearing, and their profile control and oil displacement capacity in deep reservoir is lower than that of the polymer.

A method for evaluating sensitivity of electromagnetic localization systems for wireless capsule endoscopes.

This paper studies the use of electromagnetic induction in localization of wireless capsule endoscopes (WECs). There is still currently a need for an accurate localization system to enable localizing possible findings in the gastrointestinal tract, and to develop an active steering system for the capsule. Developing an optimal localization system requires the sensitivity of the system to be analyzed. In this paper, three different coil geometries are modelled with a computer simulation platform, and their sensitivities and target responses are compared. In order to do that, a formulation for the sensitivity based on the dipole model approximation is presented. The first coil array is based on literature and is used as a reference. The second array presents how having more transmit-receive channels in the array effects the sensitivity. The third coil array simulates the effect of increasing the field excitation intensity in different directions by using a three-axial Helmholtz array. In addition, both proposed coil arrays utilize larger coils than the reference. As a result, it seems that both increasing the coil size and the number of field projections interrogating the target increase the overall sensitivity in the region of interest and the target response. The findings suggest that an optimal coil array could utilize both large coils and multiple transmit-receive channels to increase the number of independent fields incident onto the target.

Magnetic Resonance Wire Coil Losses Estimation with Finite-Difference Time-Domain Method

Radiofrequency (RF) coils are used to transmit and receive signals in magnetic resonance (MR) systems. Optimized RF coil design has to take into account strategies to maximize the coil performance by choosing coil sizes and geometry for achieving the best signal-to-noise ratio (SNR). In particular, coil conductor and radiative loss contributions strongly affect the SNR value, with the first mainly playing a role in low-field MR systems especially, while the second could be the dominant coil loss mechanism for high-frequency tuned coils. This paper investigates the accuracy of the finite-difference time-domain (FDTD) method for separately estimating coil conductor and radiative loss contributions. Comparison with finite element method (FEM) analysis and workbench measurements performed on a home-built coil prototype permitted us to validate the simulation results. Moreover, this research, jointly with literature data on sample-induced losses estimation, demonstrates that an FDTD-based solver permits providing an SNR model for coils with various and complicated geometries.

Simulation Study of Radio Frequency Safety and the Optimal Size of a Single-Channel Surface Radio Frequency Coil for Mice at 9.4 T Magnetic Resonance Imaging.

The optimized size of a single-channel surface radio frequency (RF) coil for mouse body images in a 9.4 T magnetic resonance imaging (MRI) system was determined via electromagnetic-field analysis of the signal depth according to the size of a single-channel coil. The single-channel surface RF coils used in electromagnetic field simulations were configured to operate in transmission/reception mode at a frequency of 9.4 T–400 MHz. Computational analysis using the finite-difference time-domain method was used to assess the single-channel surface RF coil by comparing single-channel surface RF coils of varying sizes in terms of |B1|-, |B1+|-, |B1−|- and |E|-field distribution. RF safety for the prevention of burn injuries to small animals was assessed using an analysis of the specific absorption rate. A single-channel surface RF coil with a 20 mm diameter provided optimal B1-field distribution and RF safety, thus confirming that single-channel surface RF coils with ≥25 mm diameter could not provide typical B1-field distribution. A single-channel surface RF coil with a 20 mm diameter for mouse body imaging at 9.4 T MRI was recommended to preserve the characteristics of single-channel surface RF coils, and ensured that RF signals were applied correctly to the target point within RF safety guidelines.

An Approximate Electromagnetic Model for Optimizing Wireless Charging of Biomedical Implants.

Computational modeling is increasingly used to design charging systems for implanted medical devices. The design of these systems must often satisfy conflicting requirements, such as charging speed, specific absorption rate (SAR) and coil size. Fast electromagnetic solvers are pivotal for enabling multi-criteria optimization. In this paper, we present an analytical model based on the quasi-static approximation as a fast, yet sufficiently accurate tool for optimizing inductive charging systems. The approximate model was benchmarked against full-wave simulations to validate accuracy and improvement in computation time. The coupling factor of two test coils was measured for lateral and axial displacements and the SAR was measured experimentally in a PAA phantom. The approximate model takes only 11 seconds to compute a single iteration, while the full-wave model takes 5 hours to compute the same case. The maximum difference with full-wave simulations was less than 24% and the mean difference less than 2%. Adding a novel figure of merit into the multi-criterion optimization resulted in a 16% higher charging speed. The measured results of the SAR and coupling factor are within a 5 mm coil offset margin. The proposed approximate model succeeds as a rapid prototyping tool, enabling fast and sufficiently accurate optimization for wireless charging systems. The approximate model is the first of its kind to compute both the coupling factor and the SAR near conducting structures fast enough to enable optimization of charging speed.

Integration of HTS Coils in a Lab-Scale Modular Multilevel Converter

High-temperature superconducting coils are achieving technological maturity to be integrated into medium and high-voltage direct current applications. We propose to replace the conventional air-core dry-type arm coils of a modular multilevel converter with high-temperature superconducting coils. The goal is to reduce the the size and weight of arm coils, reduce losses under normal operation and limit the current under fault conditions. To demonstrate the feasibility of this proposition, we integrate air-core superconducting pancake coils in the arms of a single-phase modular multilevel converter prototype. The pancake coils were wound with BSCCO tapes. In this article, we detail the construction of the cryo-MMC and report the first experimental results.

Benefits and Challenges of Advanced Divertor Configurations in DEMO

The divertor design and configuration define the power exhaust capabilities of DEMO, and act as a major design driver. They set a number of requirements on the tokamak layout, including port sizes, poloidal field coil positions, and size of toroidal field coils. It also requires a corresponding configuration of plasma-facing components (PFCs) and a remote handling scheme to be able to handle the cassettes and associated in-vessel components the configuration requires.There is a risk that the baseline ITER-like single-null (SN) divertor configuration cannot meet the PFC technology limits regarding power exhaust while achieving the target plasma performance requirements of DEMO or a future fusion power plant. Alternative magnetic configurations (AMCs) – for example, double-null, snowflake, and super-X – exist and potentially offer mitigation solutions to these risks and a route to achievable power handling in DEMO. However, these options impose significant changes on machine architecture, increase the machine complexity and affect remote handling and plasma physics and so an integrated approach must be taken to assessing the feasibility of these options.This paper describes work carried out to define a set of design limitations that any alternative divertor configuration for DEMO must consider, and assesses the feasibility of integration of a set of potential AMCs for DEMO.

Inductanceless high order low frequency filters for medical applications

&lt;p&gt;In this paper, a designed circuit used for low-frequency filters is implemented and realized the filter is based on frequency-dependent negative resistance (FDNR) as an inductor simulator to substitute the traditional inductance, which is heavy and high cost due to the coil material manufacturing and size area. The simulator is based on an active operation amplifier or operation transconductance amplifier (OTA) that is easy to build in an integrated circuit with a minimum number of components. The third and higher-order Butterworth filter is simulated at low frequency for low pass filter to use in medical instruments and low-frequency applications. The designed circuit is compared with the traditional proportional integral controller enhanced (PIE) and T section ordinary filter. The results with magnitude and phase response were compared and an acceptable result is obtained. The filter can be used for general applications such as medical and other low-frequency filters needed.&lt;/p&gt;

Simulation Analysis of Eddy Current Testing Parameters for Surface and Subsurface Defect Detection of Aviation Aluminum Alloy Plate

In the process of eddy current testing (ECT) of surface and subsurface defects of aviation aluminum alloy plates, the setting of parameters is important to the test results. Inappropriate test parameters can cause false detection or even missed detection of defects. To address this problem, the effects of probe type, coil size, and excitation frequency on the accurate identification and quantitative evaluation of surface and subsurface defect detection were studied and analyzed in this study to determine the best testing parameters. The experimental results show that the absolute probe with an outer radius of 3.3 mm has better detection performance for aviation aluminum alloy plate defects. There are different optimal excitation frequency ranges for the surface and subsurface defects. An excitation frequency of 80 kHz to 90 kHz can be used for the detection of unknown defects.

Effects of the Cerebral Aneurysm Treatment Method on Coil Packing Density and Its Relationship with the Ostium Area

PurposeTo test the following hypotheses: (a) balloon or stent assistance increases coil packing density (CPD) in the endovascular treatment of intracranial aneurysms, and (b) CPD correlates to ostium area (OA) and aneurysm volume (AV). Materials and MethodsThis retrospective study included 60 aneurysms (54 ruptured and 6 unruptured) treated with simple coiling (SC) (n = 18), balloon-assisted coiling (BAC) (n = 7), or stent-assisted coiling (SAC) (n = 35) at the authors’ institution between August 2017 and December 2019. AV and OA measurements were obtained from 3-dimensional digital subtraction angiography images using commercial software. Coil sizes were retrieved from patient files, and coil volume (CV) measurements were obtained from https://www.angiocalc.com/. Analysis of covariance, multivariate covariance analysis, and Pearson correlation analyses were performed. ResultsThe median value for AV, CV, CPD, and OA was 63.4 mm3 (range, 5.5–1,771.4 mm3), 23.13 mm3 (range, 2.03–296.95 mm3), 33.29% (range, 13.41%–81.02%), and 10.7 mm2 (range, 2.7–49.9 mm2), respectively. Multivariate analysis showed that the CPD values were not significantly different among the treatment groups, although OA significantly differed between the SC and SAC groups (P < .05). Pearson correlations showed that similar to AV, OA was negatively correlated with CPD (r = −0.321, P < .05). ConclusionsThe CPD value in cerebral aneurysms treated with BAC or SAC did not differ from that in aneurysms treated with SC.

Efficient wireless power transmission to remote the sensor in restenosis coronary artery

In this study, the researchers have proposed an alternative technique for designing an asymmetric 4 coil-resonance coupling module based on the series-to-parallel topology at 27 MHz industrial scientific medical (ISM) band to avoid the tissue damage, for the constant monitoring of the in-stent restenosis coronary artery. This design consisted of 2 components, i.e., the external part that included 3 planar coils that were placed outside the body and an internal helical coil (stent) that was implanted into the coronary artery in the human tissue. This technique considered the output power and the transfer efficiency of the overall system, coil geometry like the number of coils per turn, and coil size. The results indicated that this design showed an 82% efficiency in the air if the transmission distance was maintained as 20 mm, which allowed the wireless power supply system to monitor the pressure within the coronary artery when the implanted load resistance was 400 Ω.

Coolant Wetting Simulation on Simplified Stator Coil Model by the Phase-Field Lattice Boltzmann Method.

Stator coils of automobiles in operation generate heat and are cooled by coolant poured from above. The flow characteristic of the coolant depends on the coil structure, flow condition, solid–fluid interaction, and fluid property, which has not been clarified due to its complexities. Since straight coils are aligned and layered with an angle at the coolant-touchdown region, the coil structure is simplified to a horizontal square rod array referring to an actual coil size. To obtain the flow and wetting characteristics, two-phase fluid flow simulations are conducted by using the phase-field lattice Boltzmann method. First, the flow onto the single-layered rod array is discussed. The wetting area is affected both by the rod gap and the wettability, which is normalized by the gap and the averaged boundary layer thickness. Then, the flow onto the multi-layered rod arrays is investigated with different rod gaps. The top layer wetting becomes longitudinal due to the reduction of the flow advection by the second layer. The wetting area jumps up at the second layer and increases proportionally to the below layers. These become remarkable at the narrow rod gap case, and finally, the dimensionless wetting area is discussed at each layer.

Extensibility-Enriched Spinnability and Enhanced Sorption and Strength of Centrifugally Spun Polystyrene Fiber Mats

We show that incorporating ultrahigh molecular weight (UHMw) polymer fractions into spinning dopes improves their spinnability and facilitates the centrifugal force spinning (CFS) of polystyrene (PS) fiber mats with enhanced mechanical and sorption properties. For matched polymer concentration, c, and solvent type, the UHMw additive at a low weight fraction (<0.1) only weakly influences shear viscosity. We attribute the enhanced spinnability and fiber properties to change in extensibility (stretched to equilibrium coil size ratio), quantified using the extensibility-averaged molecular weight, ML, that accounts for the role of stretched chain hydrodynamics and extensional rheology response. Although many studies argue that spinnable solutions lie above the entanglement concentration on the c–Mw plots, we show that the UHMw additives facilitate fiber formation below the computed entanglement concentration for extensibility-enriched (EE) polymer solutions. We highlight the role of extensibility and dispersity by locating the minimum spinnable concentration, cspin, and the concentration, cBC, for the transition from beaded to continuous fiber formation on a c–ML plot. We show that extensibility-enriched solutions display cspin ∝ ML–b with b = 1 + ν and cBC ∝ ML–b with b = 3ν – 1 due to significant strain hardening and large Trouton ratios that delay pinch-off. Additionally, we posit that in low-extensibility solutions, including low Mw or lower flexibility polymers, spinnability benefits from the steep viscosity increase on the solvent loss for volatile entangled (VE) polymer solutions, requiring cspin ∝ ce ∝ MW–b with b = 1 + ν, explaining why entanglements promote fiber formation.

Seeking Solvation: Exploring the Role of Protein Hydration in Silk Gelation.

The mechanism by which arthropods (e.g., spiders and many insects) can produce silk fibres from an aqueous protein (fibroin) solution has remained elusive, despite much scientific investigation. In this work, we used several techniques to explore the role of a hydration shell bound to the fibroin in native silk feedstock (NSF) from Bombyx mori silkworms. Small angle X-ray and dynamic light scattering (SAXS and DLS) revealed a coil size (radius of gyration or hydrodynamic radius) around 12 nm, providing considerable scope for hydration. Aggregation in dilute aqueous solution was observed above 65 °C, matching the gelation temperature of more concentrated solutions and suggesting that the strength of interaction with the solvent (i.e., water) was the dominant factor. Infrared (IR) spectroscopy indicated decreasing hydration as the temperature was raised, with similar changes in hydration following gelation by freezing or heating. It was found that the solubility of fibroin in water or aqueous salt solutions could be described well by a relatively simple thermodynamic model for the stability of the protein hydration shell, which suggests that the affected water is enthalpically favoured but entropically penalised, due to its reduced (vibrational or translational) dynamics. Moreover, while the majority of this investigation used fibroin from B. mori, comparisons with published work on silk proteins from other silkworms and spiders, globular proteins and peptide model systems suggest that our findings may be of much wider significance.

Linear and Nonlinear Viscoelasticity of Polypropylene Containing Cross‐Linked Gels

AbstractThe dynamic viscoelastic and elongational flow behaviors of polypropylene (PP) with increased loading of micron‐sized gelled particles have been investigated. The results reveal that incorporating gel particles can significantly enhance the PP melt storage and loss modulus, complex viscosity, and degree of strain hardening. The gel particle, acting as a soft, deformable filler, exhibits a core–corona structure. The core is made of cross‐linked PP, with the corona region consisting of chain loops, dangling chains, and strongly constrained PP matrix chains. The matrix chains bridge globally between the adjacent gel particles once the interparticle distance is shorter than the PP random coil size. This, in turn, results in a gel‐like behavior of the entire PP matrix. The present findings serve to advance fundamental understanding on the rheological behavior of polymeric systems containing self‐similar soft particles for improving melt strength.