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2018 CLEO, San Jose, United States

May 13 - 17, 2018 (Mon - Fri), San Jose Convention Center

 

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<Oral Session>

Electrically Controllable Reconfiguration of Terahertz Meta-Atoms into Meta-Molecules

Hyunseung Jung, Jaemok Koo, Wonwoo Lee, Moon Sung Kangand Hojin Lee

 

 Abstract

We report structural methodology for electrically switchable terahertz metamaterials between atom- and molecule-states by using limited conductance variation of graphene bridges. Based on experimental verification, we confirmed 39% of wide resonance tuning of terahertz metamaterials.

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2018 SPIE Optics + Photonics, San Diego, United States

Aug 19 - 23, 2018 (Sun - Thu), San Diego Convention Center

 

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<Oral Session>

Electrically controlled terahertz funneling for electromagnetically induced transparency analogue

Hyunseung Jung, Hyunwoo Jo, Wonwoo Lee, Moon Sung Kangand Hojin Lee

 

 Abstract

In this study, we propose an electrically switchable funneling of terahertz waves for electrically induced transparency (EIT) analogue by actively controllable metamaterial. The proposed EIT metamaterials consist of the orthogonally combined metallic cut-wire (CW) pair and pseudo complimentary cut-wire (CCW), where graphene lines are laid on the center of pseudo-CCW to control the funneling of terahertz waves at the transmission resonance of the EIT structure by using ion-gel coplanar gating system. In experimental results, we successfully show the modulation depth of 54.9% and the group delay change by 1 ps at the transmission peak of our EIT analogue.

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2018 SPIE Optics + Photonics, San Diego, United States

Aug 19 - 23, 2018 (Sun - Thu), San Diego Convention Center

 

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<Poster Session>

Tandem structured 2-color micro-polymer light-emitting diodes (μ-PLEDs) 

Keun-Yeong Choi, Han Wool Park, Do Hwan kim, and Hojin Lee

 

 Abstract

In this study, we proposed a tandem structured 2-color micro-polymer light-emitting diodes (μ-PLEDs) for super high-resolution organic light-emitting diodes (OLEDs) micro displays. The proposed 2-color polymer light-emitting diodes consisted of red and green colored polymers patterned to 20 μm. For the tandem structure, we adopted the recently developed sol-gel process to obtain the orthogonality of organic semiconductor against the solvents and chemicals so that we could apply the standard photo-lithography and dry-etch process to achieve micron-size patterns of light-emitting polymers. Experimental results showed that we could achieve the maximum luminance of the tandem structured 2-color PLEDs up to 140 cd/m2 at 8V

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2018.09.04 14:03

2018 iMiD, Busan, Korea

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2018 iMiD, Busan, Korea

August 28 - 31, 2017 (Tue. - Fri.), Exhibition Center I, BEXCO 


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High-Speed Electroactive Polymer Actuator for Artificial Muscle

Yongchan Kim, So Young Kim, Dayoon Lee, Eunsong Ji, Do Hwan Kim, and Hojin Lee

 

 Abstract

With the development of bio-friendly soft electronic devices, artificial muscles that mimic the shapes and functions of natural muscles are attracting attention in various fields. Recently, the artificial muscles represent soft actuators. They have many advantages such as high flexibility, light density, and low power consumption. Due to these characteristics, many studies about artificial muscles are being carried out in various fields such as soft robot, prosthetics, and haptic applications. Especially, among various soft actuators, ionic polymer actuators have been attracted much interest as the advantage of low driving voltage and flexibility using volume changing due to the movement of ions in an ionic polymer layer. However, artificial muscles based on ionic polymer suffer from low displacement and force at high operating frequencies. 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 this talk, we propose a high-speed ionic polymer muscle using ionic polymer and conducting polymer (PEDOT:PSS) solution with ionic liquid and DMSO as additive by spray coating method. Also, through these methods our actuator could control an interface structure from nano to micro size between ionic polymer and electrodes. The actuator implemented by us was successfully operated with a large displacement up to 3mm (strain=0.4%) at an operating frequency of 1Hz under an applied voltage of 2V. Further, the actuator shows high-speed response under the bending strain of 0.1% and the displacement of 0.67mm even at frequency of 30Hz. 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 nanostructured ion conducting channel, thereby leading to larger displacement and faster response of actuators even under low voltage bias. We believe that high-speed ionic polymer actuator demonstrated by us will be an effective way to implement a novel engineering design for artificial muscle capable of physiologically actuating under electrical stimuli. In this talk, we propose a high-speed ionic polymer muscle using ionic polymer and conducting polymer (PEDOT:PSS) solution with ionic liquid and DMSO as additive by spray coating method (Fig. 1). Also, 

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2018.09.06 12:13

2018 iMiD, Busan, Korea

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2018 iMiD, Busan, Korea

August 28 - 31, 2017 (Tue. - Fri.), Exhibition Center I, BEXCO 


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Tandem structured 2-color micro-polymer light-emitting diodes (μ-PLEDs)

Keun-Yeong Choi, Han Wool Park, Do Hwan Kim and Hojin Lee

 

 Abstract

Recently organic light emitting diodes (OLED) displays have been selected for commercial mobile devices, curved TVs and Virtual Reality (VR) because of their advantages such as high contrast, high response speed, and wide viewing angle. Typically, OLED pixels are fabricated using thermal evaporation and shadow mask. However, using a shadow mask creates a limitation in implementing high-resolution pixels into the display panel. In order to achieve micronsize OLED pixels, many different approaches had been reported for patterning OLED layers into micron-size such as ink-jet printing, imprinting, and adopting orthogonal photo-resisit. however, created addition problems of luminance degradation, limited panel-size, or increased production costs. Previously, we developed a sol-gel process to obtain the orthogonality of organic semiconductor against the solvents and chemicals so that we could apply the standard photo-lithography and dry-etch process to achieve micron-size patterns of light-emitting polymers[1]. Using this mechanism, we could successfully fabricated a CMOS circuits with micron-patterned n- and p-type organic semiconductors through sequential solution processes based on standard photolithograph. Through, we confirmed the feasibility of fabrication various electron device by using a sol-gel process. In this paper, we fabricated 2-color PLEDs with micropatterns of light-emitting polymer semiconductor through sequential solution processes. Fig. 1. (a) shows the optical microscopy image of patterned pixels (20 μm×20 μm) of light-emitting polymer semiconductor that were fabricated by using standard photolithography and dry-etch processes. Fig. 1. (b) shows the electroluminescence (EL) operation of 2-color PLEDs with micropatterns of lightemitting polymer semiconductor. Finally, we confirmed that the maximum luminance of the tandem structured 2- color PLEDs was 140 cd/m2 at 8V. 

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