• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.401-415
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• 2021

Soft robots are promising devices for applications in drug delivery, sensing, and manufacturing. Traditional hard robotics are manufactured with rigid materials and their degrees of motion are constrained by the orientation of the joints. In contrast to rigid counterpart, soft robotics, employing soft and stretchable materials that easily deforms in shape, can realize complex motions (i.e., locomotion, swimming, and grappling) with a simple structure, and easily adapt to dynamic environment. Among them, the magnetic actuators exhibit unique characteristics such as rapid and accurate motion control, biocompatibility, and facile remote controllability, which make them promising candidates for the next-generation soft robots. Especially, the magnetic actuators instantly response to the stimuli, and show no-hysteresis during the recovery process, essential for continuous motion control. Here, we present the state-of-the-art fabrication process of magnetically controllable nano-/micro-composites, magnetically aligning process of the composites, and 1-dimensional/multi-dimensional multimodal motion control for the nextgeneration soft actuators.

• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.157-162
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• 2006

In this study, a high sensitive giant magnetoresistance-spin valve (GMR-SV) bio-sensing device with high linearity and very low hysteresis was fabricated by photolithography and ion beam deposition sputtering system. Detection of the Fe-hemoglobin inside in a red blood and magnetic nanoparticles using the GMR-SV bio-sensing device was investigated. Here a human's red blood includes hemoglobin, and the nanoparticles are the Co-ferrite magnetic particles coated with a shell of amorphous silica which the average size of the water-soluble bare cobalt nanoparticles was about 9 nm with total size of about 50 nm. When 1 mA sensing current was applied to the current electrode in the patterned active GMR-SV devices with areas of $5x10{\mu}m^2 $ and $2x6{\mu}m^2 $, the output signals of the GMRSV sensor were about 100 mV and 14 mV, respectively. In addition, the maximum sensitivity of the fabricated GMR-SV sensor was about $0.1{\sim}0.8%/Oe$. The magnitude of output voltage signals was obtained from four-probe magnetoresistive measured system, and the picture of real-time motion images was monitored by an optical microscope. Even one drop of human blood and nanopartices in distilled water were found to be enough for detecting and analyzing their signals clearly.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.17-23
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• 2001

The 3-D Hall sensor has two horizontal magnetic field sensing parts ($\chi$, y components) and one vertical magnetic field sensing part (z component). For conventional, 3-D Hall sensor it is general that the sensitivity for $B_{z}$ is about 1/10 compared with those for $B_\chi$ or $B_y$. Therefore, in this work, we proposed 3-D Hall sensor with new structure. We have increased the sensitivity about 6 times to form the trench using anisotropic etching. And we have increased the sensitivity for the $B_z$ by 80% compared with those of $B_\chi$ and$B_y$ using deposition of the ferromagnetic thin films on the bottom surface of the wafer to concentrate the magnetic fluxes. When the input current was 3 mA, sensitivities of the fabricated sensor with Ni/Fe film for $B_\chi, B_y$ and $B_{z}$ were measured as 120.1 mV/T, 111.7 mV/T, 95.3 mV/T, respectively. The measured linearity of the sensor was within $\pm$3% of error.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.18-25
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• 2013

MFL PIG (Magnetic Flux Leakage Pipeline Inspection Gauge) is called the system which detects the defect for underground pipelines by using magnetic flux leakage method in nondestructive testing. This method is very suitable for testing pipelines because pipeline has high magnetic permeability. MFL PIG generates the magnetic fields to the pipe axially oriented, and detect the signal of leakage flux by using hall sensor. However, MFL PIG is hard to detect the axially oriented crack with small size because the magnetic flux leakage is not enough to be occurred. To detect the small size and axially oriented crack, the circumferential MFL (CMFL) PIG is being proposed and it can maximize the leakage flux for the axial crack by performing magnetic fields circumferentially on the pipe. In this paper, CMFL PIG is applied to detect the axially oriented crack with small size and the analysis for the distribution and the amplitude of the leakage flux signal is performed by using three dimensional finite element method. From sensing signals, the method how to determine the shape of axially oriented cracks is proposed and verified with experiment.

• Journal of Sensor Science and Technology
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• v.21 no.5
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• pp.339-344
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• 2012

This article describes a novel method for the detection of amyloid-${\beta}$($A{\beta}$) peptide that utilizes a photo-sensitive field-effect transistor (p-FET). According to a recent study, $A{\beta}$ protein has been known to play a central role in the pathogenesis of Alzheimer's disease (AD). Accordingly, we investigated the variation of photo current generated from p-FET with and without intracellular magnetic beads conjugated with $A{\beta}$ peptides, which are placed on the p-FET sensing areas. The decrease of photo current was observed due to the presence of the magnetic beads on the channel region. Moreover, a similar characteristic was shown when the Raw 264 cells take in magnetic beads treated with $A{\beta}$ peptide. This means that it is possible to simply detect a certain protein using magnetic beads and a p-FET device. Therefore, in this paper, we suggest that our method could detect tiny amounts of $A{\beta}$ for early diagnosis of AD using the p-FET devices.

• Journal of Magnetics
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• v.8 no.1
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• pp.24-31
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• 2003

The discoveries of antiferromagnetic coupling in Fe/Cr multilayers by Grunberg, the Giant Magneto Resistance by Fert and Grunberg and a large tunneling magnetoresistance at room temperature by Moodera have triggered enormous research on magnetic thin films and magnetoelectronic devices. Large opportunities are especially opened by the spin dependent tunneling resistance, where a strong dependence of the tunneling current on an external magnetic field can be found. We will briefly address important basic properties of these junctions like thermal, magnetic and dielectric stability and discuss scaling issues down to junction sizes below 0.01 $\mu\textrm{m}$$^2$with respect to single domain behavior, switching properties and edge coupling effects. The second part will give an overview on applications beyond the use of the tunneling elements as storage cells in MRAMs. This concerns mainly field programmable logic circuits, where we demonstrate the clocked operation of a programmed AND gate. The second 'unconventional' feature is the use as sensing elements in DNA or protein biochips, where molecules marked magnetically with commercial beads can be detected via the dipole stray field in a highly sensitive and relatively simple way.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.395-400
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• 2013

In this paper, we introduce the implementation of high accurate level sensor system using the pulse wave type magnetostriction sensor. When a current pulse flows along the waveguide, the magnetic field also propagates towards the end of waveguide. When this magnetic field just passes the position of the magnet for level detection, the resultant magnetic field by these two magnetic fields makes a torsional reflected signal. This is used to calculate the time difference between a interrogation pulse wave and this torsional reflected signal. The key elements and characteristics were investigated to implement level sensor system based on this principle. We introduce a method to calculate the speed of ultrasonic reflected signal and how to make a model of sensing coil. In particular, we experiment with the characteristics of the torsional reflected signal according to the changes of the interrogation voltage and displacement. To make high accurate level sensor system, two methods were compared. One is to use the comparator and time counter, the other is STFT(Short Time FFT) which is capable of the time-frequency analysis.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2535-2537
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• 2000

In order to detect and monitor the broken cords of steel-cord belt from being damaged by impact of large lump of materials and the corrosion of steel cord, we developed a non-contact magnetic coil detection system. This measures the deterioration of reinforcing cables in steel cord conveyor belt which transport the ores in raw material plant. In this research, magnetic coil sensor of broken-cord detection system has exciting part and sensing part. The broken-cord detection system is operated by supplying a transmitter coil with electric power to generate magnetic field, and then the change of induced voltage is detected in each receiver coils due to resultant magnetic flux effected by the broken steel cords at the inside of the conveyor belt. By the informations such as the position and size of the broken steel cords obtained by SCBMS(Steel Cord Belt Monitoring System), it is expected that not only the span of belt life will be lengthened, but also this system can enable operators to plan scheduled maintenance and prevent the enlargement of damaged parts in steel cord belt at an early stage

• Investigative Magnetic Resonance Imaging
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• v.25 no.2
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• pp.81-92
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• 2021

The role of neuroimaging in patients with acute ischemic stroke has been gradually increasing. The ultimate goal of stroke imaging is to make a streamlined imaging workflow for safe and efficient treatment based on optimized patient selection. In the era of multimodal comprehensive imaging in strokes, imaging based on computed tomography (CT) has been preferred for use in acute ischemic stroke, because, despite the unique strengths of magnetic resonance imaging (MRI), MRI has a longer scan duration than does CT-based imaging. However, recent improvements, such as multicoil technology and novel MRI acceleration techniques, including parallel imaging, simultaneous multi-section imaging, and compressed sensing, highlight the potential of comprehensive MR-based imaging for strokes. In this review, we discuss the role of stroke imaging in acute ischemic stroke management, as well as the strengths and limitations of MR-based imaging. Given these concepts, we review the current MR acceleration techniques that could be applied to stroke imaging and provide an overview of the previous research on each essential sequence: diffusion-weighted imaging, gradient-echo, fluid-attenuated inversion recovery, contrast-enhanced MR angiography, and MR perfusion imaging.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.995-999
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• 2015

Inductive sensors are versatile and economical devices that are widely used to measure a wide variety of physical variables, such as displacement, force, and pressure. In this paper, we propose a simple inductive sensor consisting of a thin partial ring and a coil set. The self-inductance of the sensor was estimated using magnetic circuit analysis and validated through finite element analysis (FEA). The natural frequency of the ring was estimated using Castigliano's theorem and the method of equivalent mass. The estimation was validated through experiments and FEA. A prototype sensor with a signal processing circuit is built and applied to noninvasively sense the pressure inside a flexible tube. The obtained sensor outputs show quadratic behavior with respect to the pressure. When fitted to a quadratic equation, the least-square measurement error was less than 2%. The results confirm the feasibility of pressure sensing using the proposed inductive sensor.