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2016 APCCAS, Jeju, Republic of Korea

October 25 - 28, 2016 (Tue - Fri), Ramada Plaza Jeju Hotel

 

 

<Special Session : Display Driver Interface Circuits>

Design of Low-Dropout Regulator Using a-InGaZnO Thin-Film Transistors

Yongchan KimHojin Lee

 

 APCCAS 김용찬.jpg

 

 

 

Abstract

In this paper, we presented a low-dropout (LDO) regulator composed with amorphous indium-gallium-zinc-oxide thin-film transistors (a-InGaZnO TFTs) for display driving systems. Through extensive simulation works, we confirmed that the proposed LDO regulator successfully could control the output voltage levels to follow the reference input voltages, and the output voltage ripple could be suppressed below 48mV when input reference voltage was changed from 14V to 15V with 100mV fluctuation.

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2016 APCCAS, Jeju, Republic of Korea

October 25 - 28, 2016 (Tue - Fri), Ramada Plaza Jeju Hotel

 

 

<Special Session : Display Driver Interface Circuits>

On-Glass Operational Amplifier using Solution-Processed a-IGZO TFTs

Daejung Kim, Keun-Yeong ChoiHojin Lee

 

 APCCAS 최근영.jpg

 

Abstract

In this paper, we presented a novel operational amplifier (op-amp) only with solution-processed n-type amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFTs and common-source amplifier were fabricated on glass substrate through the solution process and confirmed to show stable electrical characteristics suitable for display driving circuits. Based on the experimental results, we designed an op-amp to have an overall gain of 30.5 dB, a cut-off frequency of 1.47 kHz, and a unit gain frequency of 6.65 kHz when supply voltage was ±15 V. Finally, by constituting the comparator, the proposed op-amp is expected to be used in power control and driving systems for display applications.

 

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2016 MRS fall Meeting, Boston, USA

November 27 - December 2, 2016 (Mon - Fri), John B. Hynes Veterans Memorial Convention Center

 

 

<Poster Session : BM4-16.12>

High-Speed Electroactive Polymer Actuator Engineered by Microstructured Ion Channel for Artificial Muscle 

Eunah Heo, Sangsik Park, Yongchan Kim, So Young Kim, Do Hwan Kim, and Hojin Lee

 

 MRS 김용찬.jpg

 

 

Abstract

Creating artificial muscle that emulates the capability of human muscle has been a big challenge in stretchable haptic research. In particular, ionic electroactive polymer (i-EAP) actuator has been regarded as a promising candidate for mimicking human muscle due to low operational voltage and mechanical flexibility. Artificial muscles by i-EAP actuators, however, suffer from keeping displacement and stability consistent in high operation frequencies, which comes from slow ion migration into active channel. In this manner, engineering of an optimal ion transport in the ionic films as well as mechanical properties of actuators is strongly required to allow fast actuation under electrical stimuli in the solid-state.

In this talk, we describe an unprecedented high-speed i-EAP actuator by engineering microstructure of ion channel at the interface of ionic elastomer and flexible conducting polymer electrode, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). To this end, the PEDOT:PSS electrodes are formed onto both sides of ionic elastomer with an optimal content of ions using well-controlled spray-coating method. The actuator implemented by us was successfully operated with a large displacement up to 4mm (strain=0.55%) at an operating frequency of 0.1Hz under an applied voltage of 1.5V. Further, the actuator shows high-speed response under the bending strain of 0.15% and the displacement of 0.92mm even at frequency of 30Hz, which is equivalent to 100 folds improvement compared to the values reported in the literature. This result indicates that controlling an interpenetration depth of PEDOT:PSS chains into the ionic elastomer not only decreases an internal resistance between two electrodes, but also forms more effective and microstructured ion conducting channel, thereby leading to larger displacement and faster response of actuators even under low voltage bias.

We believe that high-speed i-EAP actuator demonstrated by us will be an effective way to implement human-interactive smart haptics capable of recognizing the human-environment interface and a novel engineering design for smart artificial muscle capable of physiologically actuating under electrical stimuli. 

 

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2017 SPIE Photonics West, San Francisco, USA

January 28 - February 2, 2017 (Sat - Thu), The Moscone Center

 

2b8027e2eea5996110f39af79b8ebc0b.jpg

 

<Oral Session : Session 1: THz Sources and Detectors I>

Polarization dependent resonance manipulation by terahertz meta-molecules 

Hyunseung Jung, Eunah Heo, Jaemok Koo, Chihun In, Hyunyong Choi, Moon Sung Kang, and Hojin Lee

 

 Abstract

In this study, we propose polarization dependent resonance manipulation by meta-molecules at terahertz frequencies. The proposed meta-molecules are combined with various numbers of H-shaped meta-atoms, which we refer as ‘moleculization’ of meta-atoms. We confirm that the laterally moleculized H-shaped meta-molecules successfully realize the unique properties that can modulate the resonance frequency for the specific polarization of an incident wave, while can keep one identical resonance frequency for their orthogonal polarization direction, simultaneously. Moreover, for the vertically moleculized H-shaped meta-molecules, we also find that the electromagnetically induced transparency (EIT) –like phenomenon can be achieved for the specific polarization direction, with their exceptional field enhancement properties.

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2017 SPIE Photonics West, San Francisco, USA

January 28 - February 2, 2017 (Sat - Thu), The Moscone Center

 

e060e646f06217117ea6f1e3b202749f.jpg

 

<Oral Session : Session 7: RF-Submillimeter-Wave II>

Wireless chemical sensor system based on electromagnetically energy-harvesting metamaterials

Wonwoo Lee, Yonghee Jung, Hyunseung Jung, and Hojin Lee

 

 Abstract

We propose a novel wireless chemical sensor system by using energy-harvesting metamaterials at microwave frequencies. The proposed metamaterial sensor consists of a single split ring resonator and rectifier circuit for harvesting the energy at the specific frequency. We confirmed that the concentration of ethanol mixed with water can be detected by the proposed sensor by resonance property between the source antenna and the metamaterial which induces the variation in the energy-harvesting rate of our sensor system. Finally, we expect that our metamaterial-based wireless sensor can pave the way to the miniaturized wireless sensor systems including biochemical and dielectric environment sensors.

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