Sinyoung Cho, Jigeon Kim, Soon Moon Jeong, Min Jae Ko, Jong‐Soo Lee, Younghoon Kim,
Advances in surface chemistry and manipulation of CsPbI3 perovskite quantum dots (PQDs) have enabled the replacement of native long-chain ligands with short-chain ligands, leading to their photovoltaic applications; however, there are no reports on those of wide-bandgap and green-emitting CsPbBr3 PQDs that are promising in high-voltage and colorful building-integrated photovoltaics. Binding energies required for ligand adsorption/desorption alter according to halide compositions of PQDs because of ...
Tópico(s): Advanced Photocatalysis Techniques
2020 - American Chemical Society | Chemistry of Materials
Zheng Lin, Ji Hoon Shin, Kichang Han, Jiaywei Tsauo, Hyun‐Ki Yoon, Gi‐Young Ko, Jong Soo Shin, Kyu‐Bo Sung,
Tópico(s): Gastrointestinal Bleeding Diagnosis and Treatment
2016 - Springer Science+Business Media | CardioVascular and Interventional Radiology
Pao-Lo Liu, T.P. Lee, C.A. Burrus, I. P. Kaminow, Jong Soo Ko,
An experimental set-up for the observation of transient spectra and mode partition noise of InGaAsP injection lasers in real time is described. The build-up times for the dominant mode in various lasers are compared.
Tópico(s): Semiconductor Lasers and Optical Devices
1982 - Institution of Engineering and Technology | Electronics Letters
I. P. Kaminow, L.W. Stulz, Jong Soo Ko, A.G. Dentai, R. E. Nahory, J. C. DeWinter, R. L. Hartman,
The ridge waveguide configuration is shown to provide reliable low-threshold fundamental-transverse-mode lasers that are readily fabricated. Two variants are described: in the simple ridge laser, the 1.3 μm bandgap active layer is sandwiched between InP layers and in the cladded ridge, the active layer is surrounded by 1.1 μm bandgap InGa AsP. Thresholds as low as 34 mA and efficiencies as high as 66 percent are observed. Output power is linear to more than 12 mW. Several lasers have been operated ...
Tópico(s): Semiconductor Quantum Structures and Devices
1983 - IEEE Photonics Society | IEEE Journal of Quantum Electronics
Hyun Woo Yu, Chi Hoon Lee, Phill Gu Jung, Bo Sung Shin, Joonho Kim, Kyu-Youn Hwang, Jong Soo Ko,
Polymethyl methacrylate (PMMA) microstructures were fabricated by a polymeric microreplication technology using ultrasonic vibration energy. A commercial ultrasonic welder system was used to apply ultrasonic vibration energy for micromolding. Two different types of nickel micromolds, which were equipped with pillar-type and pore-type microstructures, were fabricated. PMMA was used as the polymer microreplication material, and the optimal molding times were determined to be 2 s and 2.5 s for the pillar- ...
Tópico(s): Additive Manufacturing and 3D Printing Technologies
2009 - SPIE | Journal of Micro/Nanolithography MEMS and MOEMS
Ko Tae Sung, Jong‐Soo Lee, Seong Yeol KIm,
Tópico(s): Osteoarthritis Treatment and Mechanisms
2009 - | Journal of Korean Medicine Rehabilitation
Sung Jin Hwang, Dong Joon Oh, Phill Gu Jung, Sang Min Lee, Jeung Sang Go, Joonho Kim, Kyu-Youn Hwang, Jong Soo Ko,
This paper presents a new polydimethylsiloxane (PDMS) dry-etching method that uses microwave plasma. The applicability of the method for fabricating microstructures and removing residual PDMS is also verified. The etch rate of PDMS was dominantly influenced by the gas flux ratio of CF4/O2 and the microwave power. While the PDMS etch rate increased as the flux ratio of CF4 was increased, the etch rate decreased as the flux ratio of O2 was increased. The maximum etch rate of 4.31 µm min−1 was achieved ...
Tópico(s): Nanofabrication and Lithography Techniques
2009 - IOP Publishing | Journal of Micromechanics and Microengineering
Byunggeon Park, Cheoljae Lee, Young‐Jun Kim, Jinhyoung Park, Hyeok Kim, Young Jin Jung, Jong Soo Ko, Sang‐Woo Kim, Ju‐Hyuck Lee, Hanchul Cho,
Herein, a new strategy for micro/nanoparticles removal in water using a triboelectric nanogenerator (TENG) is demonstrated. Removal process based on electrophoretic force can extract particles from water by its zeta potential due to the electric fields generated by the TENG, in other words, higher performance TENG removes more particles. High-performance TENG based on a three-dimensional porous-pyramid polydimethylsiloxane shows a power output nearly three times higher than that of a flat film-based ...
Tópico(s): Dielectric materials and actuators
2022 - Elsevier BV | Nano Energy
Young Jin Jung, Jungrak Choi, Wookjin Lee, Jong Soo Ko, Inkyu Park, Hanchul Cho,
Abstract Modifying the surface morphology of an elastomer surface into 3D microstructures is crucial for various soft sensor applications. However, processes based on typical mold microfabrication and elastomer casting remain the dominant methodologies. This study demonstrates a novel strategy for generating 3D and irregular microdome structures for flexible pressure sensors through the internal popping of microspheres. When thermal treatment is applied to a composite film composed of microspheres ...
Tópico(s): Gas Sensing Nanomaterials and Sensors
2022 - Wiley | Advanced Functional Materials
Dong Hwan Kim, Dong Hwa Kwak, Hyeong Jun Tak, Young Mee Jung, Kyungkuk Jung, Sang‐Hu Park, Jong Soo Ko,
This paper introduces a facile synthesis method comprising the use of a wet chemical method of a CuO/Cu(OH)2 nanowire (NW) film transformed from a Cu layer, and its utilities of transparency, anti-fogging, and self-cleaning are demonstrated. Two key parameters are considered for achieving high transparency: the thickness of the Cu layer and the reaction time in the wet chemical solution. A 40-nm-thick Cu layer deposited by a thermal evaporator is used to form CuO/Cu(OH)2 NWs with a reaction time ...
Tópico(s): Fluid Dynamics and Thin Films
2022 - Elsevier BV | Applied Surface Science
Young Jin Jung, Kyung Kuk Jung, Dong Hwan Kim, Dong Hwa Kwak, Seokyoung Ahn, Jeong Sam Han, Jong Soo Ko,
The development of flexible and sensitive three-axis pressure sensors is of great interest for various wearable applications, such as electronic skin, soft robotics, and health monitoring. This study aims to propose a highly sensitive and flexible pressure sensor that can measure three-axis pressure based on conductive microstructured carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) elastomer with a simple and large-scale fabrication method that uses a polymer wet etching process. The randomly ...
Tópico(s): Gas Sensing Nanomaterials and Sensors
2021 - Elsevier BV | Sensors and Actuators A Physical
Byunggeon Park, Young Jin Jung, Jong Soo Ko, Jinhyoung Park, Hanchul Cho,
Highly flexible and compressible porous polyurethane (PU) structures have effectively been applied in capacitive pressure sensors because of the good elastic properties of the PU structures. However, PU porous structure-based pressure sensors have been limited in practical applications owing to their low durability during pressure cycling. Herein, we report a flexible pressure sensor based on a three-dimensional porous structure with notable durability at a compressive pressure of 500 kPa facilitated ...
Tópico(s): Dielectric materials and actuators
2021 - Multidisciplinary Digital Publishing Institute | Polymers
Young Jin Jung, Tae-Han Lee, Jiyoon Oh, Byunggeon Park, Jong Soo Ko, Hyeok Kim, Jong Pil Yun, Hanchul Cho,
Capacitive pressure sensors based on porous structures have been extensively explored for various applications because their sensing performance is superior to that of conventional polymer sensors. However, it is challenging to develop sufficiently sensitive pressure sensors with linearity over a wide pressure range owing to the trade-off between linearity and sensitivity. This study demonstrates a novel strategy for the fabrication of a pressure sensor consisting of stacked carbon nanotubes (CNTs) ...
Tópico(s): Tactile and Sensory Interactions
2021 - American Chemical Society | ACS Applied Materials & Interfaces
Jae Hyuk Choi, Myung Gyu Shin, Young Jin Jung, Dong Hwan Kim, Jong Soo Ko,
In this study, we fabricated strain sensors by aligning silver nanowires and transferring them with polydimethylsiloxane (PDMS) and compared the performances of the fabricated strain sensors along the alignment direction. Two types of flexible strain sensors embedded with the aligned silver nanowires were fabricated: one in the longitudinal direction, which is the same as the alignment direction, and the other in the lateral direction, which is perpendicular to the alignment direction. We then evaluated ...
Tópico(s): Conducting polymers and applications
2020 - Multidisciplinary Digital Publishing Institute | Micromachines
Young Jin Jung, Wookjin Lee, Kyungkuk Jung, Byunggeon Park, Jinhyoung Park, Jong Soo Ko, Hanchul Cho,
In recent times, polymer-based flexible pressure sensors have been attracting a lot of attention because of their various applications. A highly sensitive and flexible sensor is suggested, capable of being attached to the human body, based on a three-dimensional dielectric elastomeric structure of polydimethylsiloxane (PDMS) and microsphere composite. This sensor has maximal porosity due to macropores created by sacrificial layer grains and micropores generated by microspheres pre-mixed with PDMS, ...
Tópico(s): Tactile and Sensory Interactions
2020 - Multidisciplinary Digital Publishing Institute | Polymers
Dong Hwan Kim, Young Jin Jung, Kyungkuk Jung, Dong Hwa Kwak, Dong Min Park, Myung Gyu Shin, Hyeong Jun Tak, Jong Soo Ko,
Abstract We propose a highly sensitive capacitive pressure sensor made of hollow polydimethylsiloxane (PDMS) foam with a three-dimensional network structure. The stiffness of the foam is adjusted by the viscosity of the PDMS solution. The fabricated PDMS-30 (PDMS 30 wt%) foam shows extremely high porosity (> 86%) approximately 19 times that of bare PDMS (PDMS 100 wt%) foam. Capacitive pressure sensors fabricated using the foam possess high sensitivity, good compressibility (up to 80% strain), and consistent ...
Tópico(s): Tactile and Sensory Interactions
2020 - Springer Science+Business Media | Micro and Nano Systems Letters
Young Jin Jung, Kyung Kuk Jung, Dong Hwan Kim, Dong Hwa Kwak, Jong Soo Ko,
We developed a simple, low-cost process to fabricate a flexible pressure sensor with linear sensitivity by using a porous carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composite structure (CPCS). The working principle of this pressure sensor is based on the change in electrical resistance caused by the contact/non-contact of the CNT tip on the surface of the pores under pressure. The mechanical and electrical properties of the CPCSs could be quantitatively controlled by adjusting the concentration ...
Tópico(s): Conducting polymers and applications
2020 - Multidisciplinary Digital Publishing Institute | Polymers
Anna L. Hagstrom, Hak-Lae Lee, Myung‐Soo Lee, Hyun‐Seok Choe, Joori Jung, Byunggeon Park, Won‐Sik Han, Jong Soo Ko, Jae‐Hong Kim, Jae‐Hyuk Kim,
Triplet-triplet annihilation upconversion (TTA-UC) has recently drawn widespread interest for its capacity to harvest low-energy photons and to broaden the absorption spectra of photonic devices, such as solar cells. Although conceptually promising, effective integration of TTA-UC materials into practical devices has been difficult due to the diffusive and anoxic conditions required in TTA-UC host media. Of the solid-state host materials investigated, rubbery polymers facilitate the highest TTA-UC ...
Tópico(s): Photonic Crystals and Applications
2018 - American Chemical Society | ACS Applied Materials & Interfaces
Kyung Kuk Jung, Young Jin Jung, Chang Jun Choi, Jong Soo Ko,
We propose a new superhydrophobic surface that contains a carbon nanotube (CNT)-implanted poly(dimethylsiloxane) (PDMS)/adhesive multilayer. The adhesive provides very strong adhesion between the CNT-implanted PDMS layer and the substrate, and the CNTs on the surface exhibit superhydrophobicity. Therefore, the CNT-implanted PDMS/adhesive (CIPA) layer provides a highly reliable surface for superhydrophobicity. The fabricated CIPA surface performs far better than previously reported surfaces in terms ...
Tópico(s): Adhesion, Friction, and Surface Interactions
2018 - American Chemical Society | ACS Omega
Young Jin Jung, Kyungkuk Jung, Byunggeon Park, Jae-Hyuk Choi, Dong‐Hwan Kim, Jinhyoung Park, Jong Soo Ko, Hanchul Cho,
Abstract We present a highly elastic and wearable piezoresistive strain sensor based on three-dimensional, micro-porous graphene-coated polydimethylsiloxane (PDMS) sponge suitable for being attached on human skin. The proposed strain sensors are simply fabricated by a sugar templating process and dip coating method based graphene ink in a facile and cost effective manner. The fabricated graphene-coated PDMS sponge shows highly stable mechanical properties in various tensile stress–strain test. A ...
Tópico(s): Conducting polymers and applications
2019 - Springer Science+Business Media | Micro and Nano Systems Letters
Jong Soo Ko, Myung Lae Lee, Dae-Sik Lee, Chang Auck Choi, Youn Tae Kim,
A laterally driven electromagnetic microactuator (LaDEM) is introduced, and a micro-optical switch is designed and fabricated as an application. LaDEM offers parallel movement of the microactuator to the silicon substrate surface (in-plane mode). Polysilicon-on-insulator wafers and a reactive ion etching process were used to fabricate high-aspect-ratio vertical microstructures, which allowed the equipping of vertical micromirrors. A fabricated single leaf spring had a width of 1.2 μm, thickness of ...
Tópico(s): Thermal Radiation and Cooling Technologies
2002 - American Institute of Physics | Applied Physics Letters
Jeong Sam Han, Jong Soo Ko, Youn Tae Kim, Byung Man Kwak,
In this paper we present an in-depth parametric study and structural optimization for a micro-optical switch based on the concept of a laterally driven electromagnetic microactuator (LaDEM). This utilizes the nonlinear behavior of a snap-through buckling occurring in two arch-shaped leaf springs of the switch, when actuated by a distributed Lorentz force induced along the leaf springs. A sudden jump in displacement can facilitate a large actuation stroke suitable for practical applications. The leaf ...
Tópico(s): Photonic and Optical Devices
2002 - IOP Publishing | Journal of Micromechanics and Microengineering
Jong Soo Ko, Hyun C. Yoon, Haesik Yang, Hyeon‐Bong Pyo, Kwang Hyo Chung, Sung Jin Kim, Youn Tae Kim,
This paper describes the design, fabrication, and test of a PDMS/PMMA-laminated microfluidic device for an immunosensing biochip. A poly(dimethyl siloxane) (PDMS) top substrate molded by polymer casting and a poly(methyl methacrylate) (PMMA) bottom substrate fabricated by hot embossing are bonded with pressure and hermetically sealed. Two inlet ports and an air vent are opened through the PDMS top substrate, while gold electrodes for electrochemical biosensing are patterned onto the PMMA bottom substrate. ...
Tópico(s): Microfluidic and Bio-sensing Technologies
2003 - Royal Society of Chemistry | Lab on a Chip
Chang Kun Kang, Sang Min Lee, Im Deok Jung, Phill Gu Jung, Sung Jin Hwang, Jong Soo Ko,
This paper presents a novel fabrication method of patternable silicon nanotips. The proposed fabrication method involves four steps: lithography, the first deep reactive ion etching (DRIE), removal of the photoresist and the second DRIE. The fabricated silicon nanotips are well aligned along the edges of microstructures. The plane shape of the microstructure was determined by the patterned shape of the photoresist. It means that the silicon nanotips can be patterned by the patterned shape of the ...
Tópico(s): Optical Coatings and Gratings
2008 - IOP Publishing | Journal of Micromechanics and Microengineering
Hiromi Miyoshi, Taiji ADACHI, Jungmyoung Ju, Sang‐Min Lee, Dong Jin Cho, Jong Soo Ko, Go Uchida, Yutaka Yamagata,
Topographical features are known to physically affect cell behavior and are expected to have great potential for non-invasive control of such behavior. To provide a design concept of a microstructured surface for elaborate non-invasive control of cell migration, we systematically analyzed the effect of microgrooves on cell migration. We fabricated silicon microstructured surfaces covered with SiO2 with microgrooves of various sizes, and characterized the behavior of cells moving from the flat surface ...
Tópico(s): Microfluidic and Bio-sensing Technologies
2011 - Elsevier BV | Biomaterials
Daeho Kim, Yongsung Kim, Byung Min Kim, Jong Soo Ko, Chae–Ryong Cho, Jong‐Man Kim,
This paper presents a uniform micro/nano double-roughened superhydrophobic surface with a high static contact angle (CA) and low contact angle hysteresis (CAH). The proposed micro/nano complex structured surfaces were self-fabricated simply and efficiently using a very simple and low-cost nonlithographic sequential process, which consists of aluminum (Al) sputtering, anodization of the Al layer and pore widening, without specific equipment and additional subsequent processes. The wetting properties ...
Tópico(s): Icing and De-icing Technologies
2011 - IOP Publishing | Journal of Micromechanics and Microengineering
Joonsik Park, Hyuneui Lim, Wandoo Kim, Jong Soo Ko,
The wetting property of a superhydrophobic glass surface with a micro-network of nanopillars fabricated from colloidal lithography and plasma etching is investigated in this paper. The micro-network distribution of nanospheres can be modulated by diluting the nanosphere concentration and controlling the spin rate. The micro-network of nanospheres spun on the glass surface serves as a mask for nanopillars during the plasma etching process. After the fabrication, the nano-structured surface is treated ...
Tópico(s): Fluid Dynamics and Thin Films
2011 - Elsevier BV | Journal of Colloid and Interface Science
Jong Soo Ko, Min Gon Lee, Jeong Sam Han, Jeung Sang Go, Bo-Sung Shin, Dae-Sik Lee,
In this letter, a laterally-driven bistable electromagnetic microrelay is designed, fabricated, and tested. The proposed microrelay consists of a pair of arch-shaped leaf springs, a shuttle, and a contact bar made from silicon, low temperature oxide (LTO), and gold composite materials. Silicon-on-insulator wafers are used for electrical isolation and releasing of the moving microstructures. The high-aspect-ratio microstructures are fabricated using a deep reactive ion etching (DRIE) process. The tandem- ...
Tópico(s): Innovative Energy Harvesting Technologies
2006 - Electronics and Telecommunications Research Institute | ETRI Journal
Jae Min Lee, Kyung Kuk Jung, Jong Soo Ko,
In this research, a nanostructured copper surface was fabricated using a CuSO4·5H2O solution containing boric acid. Cu and Cu2O structures simultaneously formed when the electrodeposition was performed using the CuSO4·5H2O solution. The Cu deposition ratio increased when the concentration of CuSO4·5H2O decreased or the applied current density increased. In contrast, the Cu2O deposition ratio increased when the concentration of CuSO4·5H2O increased or the applied current density decreased. A nanoplate- ...
Tópico(s): Electrohydrodynamics and Fluid Dynamics
2016 - Institute of Physics | Journal of The Electrochemical Society
Kyung Kuk Jung, Young Jin Jung, Chang Jun Choi, Jae Min Lee, Jong Soo Ko,
In this paper, the fabrication and characterization of a flexible thermoelectric generator (TEG) is presented. Bismuth telluride powder (Bi/Te) is utilized as p- and n-type thermoelectric materials, and carbon nanotubes (CNTs) are used to enhance electrical conductivity. Both the CNTs and bismuth telluride (Bi/Te) powder are mixed with a solution of polydimethyl siloxane (PDMS) as a precursor. The same PDMS used for the hybrid thermoelectric materials is also used as the substrate, making the TEG flexible ...
Tópico(s): Innovative Energy Harvesting Technologies
2016 - Elsevier BV | Current Applied Physics