Novel compact low-loss millimeter-wave filters using micromachined overlay and inverted overlay coplanar waveguide transmission lines with defected ground structures

Kim, Jong-Man,Chu, Kyongtae,Lee, Sanghyo,Lee, Dong-Kyu,Kim, Yongsung,Kim, Jung-Mu,Baek, Chang-Wook,Kwon, Youngwoo,Kim, Yong-Kweon IOP 2006 Journal of micromechanics and microengineering Vol.16 No.10

<P>This paper describes two types of novel compact low-loss millimeter-wave filters using an overlay coplanar waveguide (OCPW) line for lowpass filters and an inverted overlay coplanar waveguide (IOCPW) line for bandpass filters with periodic defected ground structures (DGSs). The OCPW and IOCPW lines are utilized to reduce the conductor and the substrate dielectric loss of the transmission lines. Also, these lines can provide a wide impedance range by controlling the overlapped area. The DGSs implemented on the transmission line have the role of size reduction and harmonic suppression of the filters. The combination of transmission lines having suspended structures and DGSs can provide great potential in terms of compact size, band rejection property and low-loss characteristics. The proposed filters are fabricated by using a micromachining technology and their RF performances are measured and analyzed. One of the proposed filters is a lowpass filter with a five-section stepped impedance topology having a periodic high–low impedance section. In this filter, the low impedance section is composed of the OCPW line with dumbbell-shaped DGSs and its length can be reduced by 52.7% compared to the OCPW line without DGSs. The measured insertion loss of this filter is lower than 0.2 dB up to 9 GHz, and significant spurious bands are not observed up to 40 GHz, resulting in a wide stop band. The other work that is presented here deals with a pi-shaped bandpass filter. This filter consists of three high impedance sections and two low impedance sections, and the line length of the high impedance section can be reduced by using the IOCPW line with spiral-shaped DGSs. The measured center frequency of the fabricated filter is 19 GHz, and the passband loss is 2.3 dB at the measured center frequency. The use of DGSs on the transmission line also enables us to suppress effectively the third-order harmonic component at 57 GHz.</P>

Novel MMIC protection technique in plasma etching process for mechanically movable RF mems antenna

Kim, Jung-Mu,Lee, Sanghyo,Kim, Yongsung,Kim, Jong-Man,Cheon, Changyul,Kwon, Youngwoo,Kim, Yong-Kweon Wiley Subscription Services, Inc., A Wiley Company 2008 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS - Vol.50 No.12

<P>In this article, we proposed the novel monolithic microwave integrated circuit (MMIC) protection technique in plasma etching process for MMIC mounted mechanically movable RF MEMS antenna. We could eliminate the distortion of radiation pattern caused by RF feed line on antenna frame and torsional hinge as using MMIC direct mounting on antenna plate instead of using external RF power source. Silicon-based mechanically movable RF MEMS antenna was released using DRIE process, which was performed on the backside of silicon substrate after MMIC mounting on RF MEMS antenna plate. An aluminum layer on the front side of RF MEMS antenna plays a role of etch stop layer for DRIE process. We measured the radiation pattern as rotating the moving plate along the vertical- and horizontal-direction hinge mechanically. We could obtain the radiation pattern without gain reduction and distortion of radiation pattern. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3089–3093, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23870</P>

Highly Flexible Electronic and Optical Films Composed of Hydrophobic and Hydrophilic Multilayers

Kim, Sungwoo,Lee, Bokyoung,Kim, Sanghyo,Bang, Joona,Cho, Jinhan WILEY-VCH Verlag 2010 Macromolecular Chemistry and Physics Vol.211 No.11

<P>We introduce a novel and efficient strategy for producing free-standing functional films via photo-crosslinking and electrostatic layer-by-layer (LbL) assembly, which can allow the build-up of hydrophilic multilayers onto hydrophobic surfaces. Hydrophobic multilayers were deposited on ionic substrates by a photo-crosslinking LbL process using photo-crosslinkable polymers. The photo-crosslinked surface was converted to an anionic surface by excess UV light irradiation. This treatment allowed also the stable adhesion between metal electrode or cationic polyelectrolyte and hydrophobic multilayers. After dissolving the ionic substrates in water, the formed free-standing films exhibited unique functionalities of inserted components within hydrophobic and/or hydrophilic multilayers.</P><P> <img src='wiley_img_2010/10221352-2010-211-11-MACP201000104-gra001.gif' alt='wiley_img_2010/10221352-2010-211-11-MACP201000104-gra001'> </P> <B>Graphic Abstract</B> <P>Electrochemical sensing or photochromic multilayers based on electrostatic interactions were deposited onto hydrophobic multilayer-coated ionic substrates after excess UV treatment. This approach can also produce the integrated functional properties of hydrophobic and hydrophilic multilayers. Furthermore, dissolution of ionic substrates in water produces highly flexible films with tailored nanostructure, flexibility, and functionalities. <img src='wiley_img_2010/10221352-2010-211-11-MACP201000104-content.gif' alt='wiley_img_2010/10221352-2010-211-11-MACP201000104-content'> </P>

Performance of Double GEM and Triple GEM

Sanghyo Han,Do-Hyung Kim,Heedong Kang,Hyosung Cho,Jang-Min Han,Kyoungkeun Jeong,Sangmook Kang,Tae-Hoon Lee,Yongkyun Kim,Yong-Sub Cho,Young-Jun Kim 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.5

The operation of a double GEM and a triple gas electron multiplier (GEM) was examined in several gas mixtures, including Ar/Isobutane, Ar/CO2, and Ar/N2. In the double GEM and the triple GEM detectors, large gains of about 5 104 and 6 105, respectively, were obtained for the Ar/Isobutane mixture. The optimum value of the transfer eld and the dependence of the collection current on the drift, transfer, and collection field strengths for the GEM voltage sharing in the double GEM are discussed. A lower operation voltage and gain limit are also reported for the case of a triple GEM.

High Performance PbS Quantum Dot/Graphene Hybrid Solar Cell with Efficient Charge Extraction

Kim, Byung-Sung,Neo, Darren C. J.,Hou, Bo,Park, Jong Bae,Cho, Yuljae,Zhang, Nanlin,Hong, John,Pak, Sangyeon,Lee, Sanghyo,Sohn, Jung Inn,Assender, Hazel E.,Watt, Andrew A. R.,Cha, SeungNam,Kim, Jong Mi American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.22

<P/><P>Hybrid colloidal quantum dot (CQD) solar cells are fabricated from multilayer stacks of lead sulfide (PbS) CQD and single layer graphene (SG). The inclusion of graphene interlayers is shown to increase power conversion efficiency by 9.18%. It is shown that the inclusion of conductive graphene enhances charge extraction in devices. Photoluminescence shows that graphene quenches emission from the quantum dot suggesting spontaneous charge transfer to graphene. CQD photodetectors exhibit increased photoresponse and improved transport properties. We propose that the CQD/SG hybrid structure is a route to make CQD thin films with improved charge extraction, therefore resulting in improved solar cell efficiency.</P>

Electrostatically driven low-voltage micromechanical RF switches using robust single-crystal silicon actuators

Kim, Jong-Man,Lee, Sanghyo,Park, Jae-Hyoung,Baek, Chang-Wook,Kwon, Youngwoo,Kim, Yong-Kweon IOP 2010 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.20 No.9

<P>In this paper, we demonstrate an electrostatic RF MEMS switch with a low actuation voltage, which is obtained simply by optimizing the design and fabrication of the robust single-crystal silicon (SCS) actuator, as well as a uniform switch performance. Through the simple approach, the pull-in voltage of the proposed electrostatic switch could be reduced simply and efficiently to approximately 10 V without sacrificing the structural stabilities and degrading the switch performances. For a total of 68 switches on a wafer, the fabrication and measurement yields were obtained to be higher than 94 and 73%, respectively. The switch performances of 50 identical switches except for 4 initially broken and 14 non-actuated switches were successfully characterized. The measured pull-in voltage was 10.7 ± 1.5 V and that of 40 switches (80%) was as low as 12 V. Nevertheless, the 50 identical switches showed considerably good and uniform performances with little deviations in terms of the RF and pull-in voltage characteristics. In addition, self-actuating behavior of the switch was not observed up to the input power of 37 dBm although the actuation voltage was reduced considerably. Low insertion losses of 0.13 ± 0.06, 0.15 ± 0.05, 0.19 ± 0.06 and 0.2 ± 0.07 dB were acquired at 2, 5, 10 and 15 GHz, respectively. The isolation characteristics could be obtained to be 41.25 ± 0.78, 33.25 ± 0.98, 27.17 ± 0.82 and 23.57 ± 0.75 at 2, 5, 10 and 15 GHz, respectively. Numerical calculations and simulations based on the fabricated results of the switches clearly demonstrated that the performance deviations among the tested switches were mainly due to the fabrication errors and not structural deformations.</P>

Development of novel complementary metal-oxide semiconductor-based colorimetric sensors for rapid detection of industrially important gases

Kim, Dami,Kim, SeJin,Kim, Sanghyo Elsevier 2018 Sensors and actuators. B Chemical Vol.265 No.-

<P><B>Abstract</B></P> <P>A sensitive and low-cost colorimetric sensor array was developed to detect industrially important gases. We selected several target gases and indicators, and then used a printing method to fabricate an array to read the color value and to analyze the data. Using the printing method, various indicators can be produced in a uniform array on a desired substrate in a short time and at a low-cost. Four gases (ammonia, methylamine, trimethylamine, and hydrazine) and ten indicators were used to confirm the ability of the gas detection system. The color change of the dyes in the array was extracted in real time using an array reader with an integrated complementary metal-oxide semiconductor (CMOS) image sensor. The developed gas detection system successfully detected gases using an array reader, which provided data for sensitive color changes in real time using the CMOS image sensor. This mechanism could be applied industrially for detecting toxic gases because the developed sensor is highly sensitive and inexpensive.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Low-cost colorimetric sensor array was developed to detect industrially important gases. </LI> <LI> The developed gas detection system successfully detected gases using an array reader. </LI> <LI> Array reader provided data for sensitive color changes in real time using the CMOS image sensor. </LI> <LI> The total gas detection system is a useful tool for early response to gas leakage accidents. </LI> </UL> </P>

A novel paper-plastic hybrid device for the simultaneous loop-mediated isothermal amplification and detection of DNA

Kim, Jae-Heon,Yoo, In Sang,An, Jeong Ho,Kim, Sanghyo Elsevier 2018 Materials letters Vol.214 No.-

<P><B>Abstract</B></P> <P>In this study, polyethersulfone (PES) paper embedded with a polymethyl methacrylate (PMMA) platform was developed for simultaneous DNA amplification and colorimetric detection. DNA was amplified using loop-mediated isothermal amplification (LAMP) in isothermal conditions in the presence of the common magnesium-dependent colorimetric indicator, eriochrome black T (EBT), to detect DNA. Here, the DNA of <I>Staphylococcus aureus</I> was used as the DNA template. The developed device was successfully used to simultaneously amplify and detect the DNA by the naked eye within 30 min with a detection limit of 1 fg/µL.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel paper-plastic hybrid device was developed to amplify and to detect DNA. </LI> <LI> We used polyethersulfone paper embedded with a polymethyl methacrylate to fabricate the device. </LI> <LI> The device was successfully used to simultaneously amplify and detect the DNA. </LI> <LI> The sensitivity of the device is high with a detection limit (LOD) of 1 fg/μL for the target DNA. </LI> </UL> </P>

An electro-conductive plane heating element for rapid thermal lysis of bacterial cells

Kim, YoungJoong,Kim, Sanghyo Elsevier 2018 Journal of microbiological methods Vol.153 No.-

<P><B>Abstract</B></P> <P>In the process of developing a point-of-care testing device, we fabricated a plane heating element using carbon paste capable of thermal lysis. The plane heating element can generate heat of 150 °C within 60 s at 0.4 A power supply within 8 W. The developed plane heating element was very effective in the extraction of DNA from both Gram-negative and Gram-positive bacteria which was further confirmed by agarose gel electrophoresis. In this approach, we aimed to eliminate expensive, time-consuming and labor-intensive procedures for the lysis of bacterial cells to extract nucleic acids to detect pathogenic bacteria accurately and swiftly.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel electro-conductive heating element was developed. </LI> <LI> It can generate heat of 150 °C within 60 s at 0.4 A </LI> <LI> It helps in rapid thermal lysis of bacterial cells. </LI> <LI> Successful in extracting DNA from bacterial cells. </LI> </UL> </P>

A rapid real-time quantification in hybrid paper-polymer centrifugal optical devices

Kim, SeJin,Kim, Dami,Kim, Sanghyo Elsevier 2019 Biosensors & bioelectronics Vol.126 No.-

<P><B>Abstract</B></P> <P>The research progress in the centrifugal microfluidic platform provides great opportunities for simple and effective analytical measurements in a variety of areas including biomedical engineering. In this study, we propose an optical reader that can measure the transmittance in a very sensitive and rapid manner on a hybrid paper-polymer centrifugal disc platform. This device enables real-time monitoring of multiple samples by measuring the absorbance of the light transmitted through the paper integrated on the disc between the light emitting diode (LED) and the photodiode (PD) regardless of the ambient light condition. To confirm its efficiency, we analyzed one of the blood's important indicators, glucose in a successful manner within 10 s without any additional complex image analysis. In addition, we discussed the results by comparing with the reflectance-based methods and with those of the previously reported studies by introducing a figure of merit to evaluate the performance of the assay.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optical reader was developed for hybrid paper-polymer centrifugal disc platform. </LI> <LI> This device enables real-time detection by measuring light transmission through the paper integrated on the disc between LED and photodiode. </LI> <LI> As proof of concept, enzymatic colorimetric glucose detection was successfully performed. </LI> <LI> Micromolar detection was achieved using the present technique within 10 s without any additional complex image analysis. </LI> </UL> </P>