Sungkyu Seo

Korea Electronics Technology Institute, Sŏngnam, Gyeonggi Province, South Korea

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Publications (14)33.79 Total impact

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    ABSTRACT: Recently lens-free imaging technology has been extensively used in the micro-particle and biological cell analysis. This is due to its high throughput, low cost, simple and compact arrangement. However this technology is still lacking in dedicated automated detection system. In this paper, we describe an automated detection method, custom developed for the lens-free imaging. For that, firstly we developed a lens-free imaging system using low cost components. This system was used to generate and capture the diffraction patterns of the micro objects. These lens free images were then processed with the custom developed algorithm. The performance of this approach was evaluated by comparing the counting results with the standard optical microscope results. Thus we evaluated the counting results for four samples of polystyrene micro beads, RBC, HepG2, HeLa and MCF-7 cell lines. The comparison shows a good agreement between the systems with correlation coefficient of 0.95 and linearity slop of 0.887. This Wi-Fi enabled lens-free imaging system along with the dedicated software possesses great potential for telemedicine applications in resource limited settings.
    IEEE Paper Contest 2014, Seoul; 12/2014
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    ABSTRACT: Recent advances in lens-free shadow imaging technology have enabled a new class of cell imaging platform, which is a suitable candidate for point-of-care facilities. In this paper, we firstly demonstrate a compact and low-cost telemedicine device providing automated cell and particle size measurement based on lens-free shadow imaging technology. Using the generated shadow (or diffraction) patterns, the proposed approach can detect and measure the sizes of more than several hundreds of micro-objects simultaneously within a single digital image frame. In practical experiments, we defined four types of shadow parameters extracted from each micro-object shadow pattern, and found that a specific shadow parameter (peak-to-peak distance, PPD) demonstrated a linear relationship with the actual micro-object sizes. By using this information, a new algorithm suitable for operation on both a personal computer (PC) and a cell phone was also developed, providing automated size detection of poly-styrenemicro-beads and biological cells such as red blood cells, MCF-7, HepG2, and HeLa. Results from the proposed device were compared with those of a conventional optical microscope, demonstrating good agreement between two approaches. In contrast to other existing cell and particle size measurement approaches, such as Coulter counter, flow-cytometer, particle-size analyzer, and optical microscope, this device can provide accurate cell and particle size information with a 2µm maximum resolution, at almost no cost (less than 100 USD), within a compact instrumentation size (9.3×9.0×9.0cm(3)), and in a rapid manner (within 1min). The proposed lens-free automated particle and cell size measurement device, based on shadow imaging technology, can be utilized as a powerful tool for many cell and particle handling procedures, including environmental, pharmaceutical, biological, and clinical applications. Copyright © 2014 Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 10/2014; · 6.45 Impact Factor
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    ABSTRACT: A novel biofilm detection platform, which consists of a cost-effective red, green, and blue light-emitting diode (RGB LED) as a light source and a lens-free CMOS image sensor as a detector, is designed. This system can measure the diffraction patterns of cells from their shadow images, and gather light absorbance information according to the concentration of biofilms through a simple image processing procedure. Compared to a bulky and expensive commercial spectrophotometer, this platform can provide accurate and reproducible biofilm concentration detection and is simple, compact, and inexpensive. Biofilms originating from various bacterial strains, including Pseudomonas aeruginosa (P. aeruginosa), were tested to demonstrate the efficacy of this new biofilm detection approach. The results were compared with the results obtained from a commercial spectrophotometer. To utilize a cost-effective light source (i.e., an LED) for biofilm detection, the illumination conditions were optimized. For accurate and reproducible biofilm detection, a simple, custom-coded image processing algorithm was developed and applied to a five-megapixel CMOS image sensor, which is a cost-effective detector. The concentration of biofilms formed by P. aeruginosa were detected and quantified by varying the indole concentration, and the results were compared with the results obtained from a commercial spectrophotometer. The correlation value of the results from those two systems was 0.981 (N = 9, P < 0.01) and the coefficients of variation (CV) were approximately threefold lower at the CMOS image-sensor platform.
    Journal of Microbiological Methods. 10/2014;
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    ABSTRACT: The complete blood count (CBC) is a routinely used method in the differential diagnosis. This includes the concentrations of red blood cell (RBC), white blood cell (WBC), platelet, and etc. However the CBC doesn’t include the information of poikilocytosis, which is a disorder of red blood cells and has various forms, i.e. elliptocyte, dacryocyte, acanthocytes, and crenated cells. Moreover, the conventional CBC detection facilities, such as flow cytometry, coulter counter, and etc., are not efficient to detect the poikilocytes. Generally poikilocytes are manually investigated by experts in a peripheral blood smear under the conventional microscope, which is time consuming and vulnerable to subjective error [1]. In this paper, we demonstrate an automated poikilocytosis detection method based on lens-free shadow imaging technique, which is a proven method for CBC [2]. In this method we extract the shadow parameters using a custom developed image processing algorithm. These shadow parameters of each cell are processed and compared with the corresponding standard microscope images, to obtain a correlation between the cell types and the shadow parameters. The results show that the shadow parameter, peak to peak distance (PDP) is strongly correlated with the cell types, which is about ~40 unit for normal RBCs and ~50 unit for crenated RBCs. Thus, the algorithm automatically differentiates the crenated and non-crenated cells by evaluating PDP of the shadow images of RBCs and the results are comparable with the standard microscope results. This type of automated detection of poikilocytosis along with CBC will provide better inside to detect uremia, pyruvate kinase deficiency, stomach cancer, and etc.
    Biochip 2014 Fall, Osong, Korea; 10/2014
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    ABSTRACT: In recent years there has been increasing interest in plasmonic nano hole array sensor. This is due to its extraordinary transmission through the sub-wavelength structures and sensitivity to the varying dielectric constant of the adjacent medium [1]. This phenomenon is largely attributed to the localized surface plasmon resonance (LSPR) effect and shows significant promise in applications such as color filters for CMOS sensor, nano lens, biosensor, and etc. [2]. Therefore LSPR sensor research is becoming a commonplace for many research laboratories to achieve high sensitivity and robustness. It has been shown that the resonance condition in the LSPR sensor varies with the change in the device parameters including thickness of the metal film, period, hole diameter, and etc. [3]. The sensitivity of this type of systems can be greatly enhanced by optimizing these device parameters. In this work we have tried to optimize a nano hole array structure for bio sensing application. For this purpose we employed the finite-difference time-domain (FDTD) simulation method for a wide range of device parameters. The optimization process was carried out for the period range of 100 – 500 nm and hole diameter of 50 – 300 nm. All these structures show a shift in the resonance wavelength for the change in the refractive index of the surrounding medium. We evaluated the performance of the device by simulating the structures for refractive index (RI) range of 1 to 2 with a resolution of 0.1 and recorded the transmitted intensity at wavelength of 626 nm and 501nm. According to the simulation data, the device with period 150 nm and hole size of 100nm on a 150nm thick gold film shows a linear response to the change in the refractive index of the surrounding medium. The result shows a shift >1.0 unit in the ratio of transmittance at wavelength 626 to 501 nm for each 0.1unit change in RI. This shift is more significant, i.e., of 1.6 unit for the change in the RI from 1.4 to 1.5. Since the device shows a linear response even for the change in RI from 1.4 to 1.5, which is the RI range of cells and biomolecules, therefore the design is suitable for bio sensing application.
    Biochip 2014 Fall, Osong , Korea; 10/2014
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    ABSTRACT: Complete blood count (CBC) is a basic and important diagnostic procedure in pathological laboratories. However, current technologies such as hemocytometry, impedancemetry, or flow-cytometry, are either time-consuming or requiring bulky and high-cost of instrumentation. To address this issue we demonstrate a compact, cost-effective, and automated blood cell counting method based on the lens-free shadow imaging technique. For that a lens-free shadow imaging technique based blood cell counting device was fabricated using a blue light emitting diode (LED) and a complementary metal oxide semiconductor (CMOS) image sensor. The shadow images of the blood cells, i.e., diffraction patterns, were captured by the device and processed automatically using a custom developed algorithm to count and differentiate the cells. The comparative study from 21 outpatient whole blood samples was carried out with the fully automated hematology analyzer (LH 750, Beckman Coulter). The comparison between the lens-free shadow imaging device and the standard reference system showed correlation indices of 0.878 for red blood cell (RBC) and 0.927 for white blood cell (WBC). The linearity comparison gave a statistical trend of y = 0.9432x with R2 = 0.99 for RBC and y = 0.7395x with R2 = 0.92 for WBC. Also the correlation coefficient for WBC subpopulations, i.e., neutrophil, lymphocyte, and monocyte, for each individual sample was >0.90. This cost-effective and compact blood cell counting system can be utilized as a powerful point of care (POC) tool, which could play an important role in primary healthcare, especially in areas with limited resources. Since the system is capable to send the images wirelessly and process them on a moderate smart phone, therefore, the proposed system possesses great potential in telemedicine applications.
    Sensors and Actuators B Chemical 10/2014; 201:321–328. · 3.84 Impact Factor
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    ABSTRACT: Effects of γ-ray irradiation on short-channel effects (SCEs) in low-doped double-gate MOSFETs are experimentally examined for various fin widths and channel lengths. The different behavior of the effects in NMOS and PMOS devices are analyzed using three-dimensional (3-D) TCAD simulation. The physical interpretation for the influence of ionizing radiation on SCEs in low-doped multi-gate MOSFETs is provided. This successfully explains not only the degradation in NMOS, but also the improvement in PMOS for subthreshold characteristics by irradiation.
    IEEE Transactions on Nuclear Science 12/2012; 59(6):3021-3026. · 1.22 Impact Factor
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    ABSTRACT: In this study, a novel mammalian cell receptor-based immuno-analytical method was developed for the detection of food-poisoning microorganisms by employing toll-like receptors (TLRs) as sensing elements. Upon infection with bacterium, the host cells respond by expressing TLRs, particularly TLR1, TLR2, and TLR4, on the outer membrane surfaces. To demonstrate the potential of using this method for detection of foodborne bacteria, we initially selected two model sensing systems, expression of TLR1 on a cell line, A549, for Escherichia coli and TLR2 on a cell line, RAW264.7, for Shigella sonnei (S. sonnei). Each TLR was detected using antibodies specific to the respective marker. We also found that the addition of immunoassay for the pathogen captured by the TLRs on the mammalian cells significantly enhanced the detection capability. A dual-analytical system for S. sonnei was constructed and successfully detected an extremely low number (about 3.2 CFU per well) of the pathogenic bacterium 5.1 h after infection. This detection time was 2.5 h earlier than the time required for detection using the conventional immunoassay. To endow the specificity of detection, the target bacterium was immuno-magnetically concentrated by a factor of 50 prior to infection. This further shortened the response to approximately 3.4 h, which was less than half of the time needed when the conventional method was used. Such enhanced performance could basically result from synergistic effects of bacterial dose increase and subsequent autocrine signaling on TLRs' up-regulation upon infection with live bacterium. This TLRs-based immuno-sensing approach may also be expanded to monitor infection of the body provided scanning of the signal is feasible.
    Analytical Chemistry 10/2012; · 5.82 Impact Factor
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    ABSTRACT: A high-throughput continuous cell monitoring technique which does not require any labeling reagents or destruction of the specimen is demonstrated. More than 6000 human alveolar epithelial A549 cells are monitored for up to 72 h simultaneously and continuously with a single digital image within a cost and space effective lens-free shadow imaging platform. In an experiment performed within a custom built incubator integrated with the lens-free shadow imaging platform, the cell nucleus division process could be successfully characterized by calculating the signal-to-noise ratios (SNRs) and the shadow diameters (SDs) of the cell shadow patterns. The versatile nature of this platform also enabled a single cell viability test followed by live cell counting. This study firstly shows that the lens-free shadow imaging technique can provide a continuous cell monitoring without any staining/labeling reagent and destruction of the specimen. This high-throughput continuous cell monitoring technique based on lens-free shadow imaging may be widely utilized as a compact, low-cost, and high-throughput cell monitoring tool in the fields of drug and food screening or cell proliferation and viability testing.
    Biosensors & Bioelectronics 05/2012; 38(1):126-31. · 6.45 Impact Factor
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    ABSTRACT: A flexible glucose sensor using a CVD-grown graphene-based field-effect-transistor (FET) is demonstrated. The CVD-grown graphene was functionalized with linker molecules in order to immobilize the enzymes that induce the catalytic response of glucose. Polyethylene terephthalate (PET) was employed as the substrate material to realize a flexible sensor. The fabricated graphene-based FET sensor showed ambipolar transfer characteristics. Through measurements of the Dirac point shift and differential drain-source current, the fabricated FET sensor could detect glucose levels in the range of 3.3-10.9 mM, which mostly covers the reference range of medical examination or screen test for diabetes diagnostic. This CVD-grown graphene-based FET sensor, which provides excellent fitting to a model curve even when deformed, high resolution, and continuous real-time monitoring, holds great promise, especially for portable, wearable, and implantable glucose level monitoring applications.
    Biosensors & Bioelectronics 05/2012; 37(1):82-7. · 6.45 Impact Factor
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    ABSTRACT: Generation of minimally diffracting beam arrays in the midfield region using periodic metal annular apertures is investigated. The relations between the patterns of the diffraction fields and the structural parameters of the periodic metal annular aperture are numerically analyzed. Material dependent transmission characteristics are also studied with finite difference time-domain simulation. The results reveal that the beam concentration efficiency and axial intensity uniformity have a trade-off restriction due to strong inter-aperture interference and surface plasmon mediates the transmission efficiency of the periodic annular apertures. The design criteria of the metal annular aperture to achieve the strong and uniform beam arrays are addressed.
    Applied Optics 03/2012; 51(8):1076-85. · 1.69 Impact Factor
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    ABSTRACT: Shadow image based high-throughput continuous cell monitoring technique is proposed. Shadow image variations of human alveolar epithelial cells (A549) cultured in a custom built incubator are analyzed qualitatively and quantitatively. Two measures which correspond to the morphology change of the cells are suggested and defined. Within this platform, it is demonstrated that a single image of a 5M pixel CMOS image sensor can monitor thousands of biological cells simultaneously and continuously. This compact, low-cost, and high-throughput cell monitoring technique holds great promise in the fields of point-of-care testing and telemedicine especially for the resource limited settings.
    01/2012;
  • Sungkyu Seo, Sang Woo Oh, Seungoh Han
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    ABSTRACT: Virtual drop test methodology based on a set of simulations is developed to evaluate the shock reliability of a MEMS (Micro Electro Mechanical System)-based sensor. The methodology consists of (1) FEM (Finite Element Method) analyses to extract the equivalent parameters of the packaged sensor, (2) a high-level simulation to determine the overall responses caused by an impact on a rigid concrete floor, and (3) another FEM simulation to evaluate whether or not the device withstands the shock by comparing the maximum stress level to the yield strengths of the materials that comprise the device. The proposed methodology accounts for the dynamic shock response as well as the stress distribution in the microstructure encapsulated by the package and thus provide insight into methods of improving the design of the device. Hence, it is expected that the proposed methodology will contribute to the effective development of robust MEMS-based sensors and their successful commercialization.
    Electronic Materials Letters 01/2011; 7(2):109-113. · 1.87 Impact Factor
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    ABSTRACT: This paper presents a technique that can provide accurate hemoglobin concentration measurement within a simple, cost-effective and compact platform. It is based on a LED and CMOS image sensor without using an environmentally harmful reagent and centrifugal process. The acquired standard curve and adequate image processing steps such as image calibration and noise suppression allow us to accurately estimate the hemoglobin concentration at an error rate of less than 2% for blind tests conducted with the 33 blood specimens of outpatients. The hemoglobin concentration measurement, one of the crucial part of the complete blood count (CBC) as well as the most commonly ordered test in clinical laboratory, within such a small, cheap and fast platform would be useful for wide applications in doctor's office and for applications in resource limited settings as a point-of-care testing tool.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2011; 157(1):103-109.