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2016 iMiD, Jeju, Republic of Korea

August 24 - 26, 2016 (Wed - Fri), ICC Jeju

 

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<Oral Session : 67. Physics of Metamaterials>

Self-Complementary Meta-Atom based Transmissive Terahertz Metasurface with High Transparency in Visible Range

Hyunseung Jung, Hojin Lee

 

 

Abstract

In the past few years, meta-surfaces for focusing and steering the incident terahertz light have been reported by using metamaterial super-cells, which consist of various metamaterial atoms to spatially change the phase of terahertz waves [1]. Particularly, the transmissive meta-surfaces, in which complementary meta-atoms are formed on the metal-plane, have been considered as meta-lenses or holograms with higher signal-to-noise ratio in comparison with reflective type metamaterials [2]. However, since they can only transmit the resonant terahertz light and are nearly opaque in other frequency ranges, there are limitations to utilize frequency resources outside their resonances. In this paper, we develop novel meta-surfaces that not only exhibit transmissive resonance but also can transparent in visible range.

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2013 iMiD, Daegu, Republic of Korea

August 26-29, 2013 (Monday - Thursday), EXCOAugust 26-29, 2013 (Monday - Thursday), EXCO

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<Poster Session : P2-54>

A Novel P-type LTPS Pixel Circuit for AMOLEDs with Dual-Compensation Function

Yeonkyung Kim, Yongchan Kim, and Hojin Lee

Abstract

In this paper, we proposed a novel voltage-programmed pixel circuit with p-type low temperature polycrystalline-silicon thin film transistor (LTPS TFT) for active-matrix organic light-emitting display (AMOLED) with an enhanced electrical stability and uniformity. Through an extensive simulation work based on p-type LTPS TFT and OLED experimental data, we confirm that the proposed pixel circuit can compensate for both mobility variation and threshold voltage shift of the driving TFT.

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SPIE Photonics West 2020, San Francisco, USA

February 1 - 6, 2020 (Sun. - Thur.), Moscone Centor


High-Performance Ionic Polymer Mechanotransducer for Soft Tactile Feedback

Yongchan Kim, Changhyeon Cho, So Young Kim, Hanbin Choi, Do Hwan Kim, and Hojin Lee



용찬_SPIE.jpg





Abstract


  In this talk, we propose an i-EAP actuator with wide bandwidth of over 200 Hz and high blocking force based on PEDOT:PSS electrode with additives and ionic-polymer with nanofibrillary network for effective haptic feedback. In particular, we developed an actuator that improves the interfacial properties between electrodes and an ionic-polymer as well as electrical conductivity of electrodes by simple and effective way through spray-coating of PEDOT:PSS solution with additives. As a result, the proposed i-EAP actuator was successfully operated with a large displacement up to 2.7 mm at an operating frequency of 20 mHz under an applied voltage of 2 V. These our actuator is capable of driving up to a high frequency of 200 Hz and shows an improved blocking force up to 0.4 mN. We believe our i-EAP actuator will provide a rational guide to future haptic feedback.

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2019.06.20 19:35

CLEO 2019, San Jose, CA, USA

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CLEO 2019, San Jose, California, USA

May 10 - 15, 2019 (Mon. - Fri.), San Jose Convention Centor


KakaoTalk_20190620_192840901.jpg


Terahertz Single-Pixel Imaging System with Electrically Tunable Metamaterial Spatial Light Modulator

Wonwoo Lee, Hyunseung Jung, Hyunwoo Jo, Moon Sung Kang, and Hojin Lee


Abstract


  Due to its penetrability and straightness of terahertz wave, terahertz imaging system has been extensively studied for real-time, high-resolution and accurate imaging systems. However, these imaging systems require high power sources or expensive and complex detectors and usually take a long time to acquire a single image. To overcome the limitations mentioned before, a single-pixel imaging system that had been used in optical imaging technique has been introduced into the terahertz range. In particular, through a single-pixel imaging system, it is possible to construct a terahertz imaging system using only a lamp and a bolometer detector instead of telescopic systems consisting of hundreds of terahertz parts, which gives great possibility for commercialization. In this work, we present electrically tunable terahertz spatial light modulator (SLM) based on ion-gel gating graphene metamaterials. From experimental results, we confirmed that the terahertz image could be successfully reconstructed corresponding to 93 % with the real object image at maximum.


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2022.07.26 14:08

CLEO 2022, San Jose, USA

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CLEO 2022, San Jose, USA

May 16 - May 20, 2022 (Mon. - Fri.), McEnery Convention Center


CLOE 조.jpg


Patch-Type Wireless Power Transfer System Based on Electromagnetic Wave Focusing Meatasurface for Bioimplantable Devices

Semin Jo, Wonwoo Lee, and Hojin Lee


Abstract


  Bioimplantable devices require miniaturization, stability, and long-term operation characteristics for electroencephalogram (EEG) monitoring and stimulation within the human body. Generally, batteries have been widely used in bioimplantable devices due to the stable power supply capability. However, bioimplantable devices using batteries have challenges in bulky size, limited lifetime, and need for replacement that essentially requires surgical method. To overcome aforementioned challenges, wireless power transfer (WPT) have attracted attention as an alternative approach to avoid the surgical procedure. Nevertheless, the stable and sustainable wireless power supply to bioimplantable devices still remains as the challenge due to the low WPT efficiency. Recently, WPT systems using metasurfaces exhibiting exotic electromagnetic (EM) characteristics were introduced in bioimplantable devices to enhance the efficiency and to reduce the geometrical dimension. In this work, we propose a novel patch-type WPT system using EM wave focusing metasurface. In contrast to previous approaches, the proposed metasurface enables to enhance the transmitted power intensity of EM wave by forming a focal point at a specific location into the tissue. Through the in-vitro experiment, the maximum voltage enhancement was confirmed at a desired depth of 10 mm in saline solution that mimics the actual tissue characteristics.

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