2016 CLEO: 2016, San Jose, USA

June 5 - 10, 2016 (Sun - Fri), San Jose Convention Center

<Poster Session : BB3-32>

Focusing of Terahertz Waves by Self-Complementary Meta-Atom toward Electromagnetically Induced Transparency

Hyunseung Jung¹, Chihun In², Hyunyong Choi², Hojin Lee¹

Abstract

Metamaterial analogues of electromagnetically induced transparency (EIT) have recently attracted worldwide researchers to realize intriguing applications such as slow light devices and nonlinear optics [1, 2]. However, conventional EIT analogues could be generated only by the destructive interference between asymmetrically arranged radiative (bright) and non-radiative (dark) atoms to produce the sharp transmission window within the broad reflection band. In this work, we studied a new way to achieve EIT-like spectral properties from a single self-complimentary meta-atom (SCM) by integrating cut-wire (CW) pair with a pseudo-complimentary cut-wire (p-CCW) structure within a unit cell. Different from the conventional EIT analogues, electric field (E-field) was highly enhanced and focused at edges of the hole and EIT-like properties are generated in the proposed SCM structure.

AMSM 2019, Incheon, Korea

October 16 - 19, 2019 (Tue. - Fri.), Sheraton Grand Incheon Hotel

Wireless Powered VOC Sensor Based on Wi Fi Energy Harvesting Metamaterial with i-TPU

Wonwoo Lee, Heejoo Park, Hyunseung Jung, So Young, Kim, Do Hwan Kim, and Hojin Lee

Abstract

  In this paper, we propose a novel wireless powered VOC sensor system based on energy harvesting metamaterial combined with ionic thermoplastic polyurethane (i TPU) gas sensing channel at microwave frequency . The sensor consists of the SRR, rectifier circuit t o harvest the RF energy by converting electromagnetic energy into DC voltage, and i TPU gas sensing channel to detect VOC with the variation of resistance. For the practical wireless sensing system, we utilized widespread and easily accessible commercial 2 .4 GHz Wi Fi source as external electromagnetic wave energy, and the energy harvesting metamaterial was designed and optimized to resonate at 2.4 GHz. When i TPU was exposed to VOC , the diffusivity of ionic liquid (IL) increases leading to decrease of the resistance of i TPU that can be identified with the differential harvested energy induced from variation of resonance property for the energy harvest ng metamaterial sensor . As a result, by analyzing the differential harvested energy , the proposed sensor c ould provide the highly sensitive wireless VOC sensor system without bulky and complicated measurement system offering great accessibility and simplicity for the practical sensor applications Also, the wireless powered VOC sensor showed high stability and repeatability representing the rapid restoring to the initial resistance value of the i TPU gas sensing channel. Finally , it is expected that the proposed system can be applied to not only for VOC sensors but also for dynamic environmental sensing systems

SPIE Photonics West 2020, San Francisco, USA

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

Active Capacitive Sensor Circuit Using Photo-Patternable Ionic Polymer Gate Dielectric Based Solution-Processed Coplanar a-InGaZnO TFTs

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

Abstract

  In this paper, we propose solution-processed coplanar a-InGaZnO TFTs using photo-patternable ionic polyurethane acrylate (i-PUA) polymer as a gate dielectric. In our fabrication process, i-PUA is able to pattern micro-size (30μm) by using photocrosslinking property and maintain high capacitance through EDL. Based on developed TFTs, we fabricated an active pixel sensor (APS) circuit consisting of three coplanar a-InGaZnO TFTs for detecting capacitance changes through the difference of output voltages. Furthermore, we simultaneously fabricated a capacitive pressure sensor using an i-PUA on the same plane so as to integrated APS circuit and capacitive pressure sensor simply. Based on the experimental results, we confirmed that the proposed APS circuit could detect changes in the capacitance through various input pressure-levels in i-PUA based sensor. With these results, we believe that our proposed sensor system using the integration of APS circuit and sensor will be applicable to future wearable, human-interaction display with low-power consumption.

KIEEME 2021, Pyeongchang, Korea

June 30 - July 2, 2021 (Wed. - Fri.), Alpensia

Design of Orthogonal Polymer Semiconductor Gels for High Physical and Chemical Resistance

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

Abstract

  Presently commercialized organic light-emitting diode (OLED) displays have limitations in implementing future high-resolution displays as fine metal mask (FMM) methods are commonly utilized to implement pixel patterns. To this end, lots of research have been done through printing methodology including inkjet printing, screen printing, and organic vapor jet printing to implement high-resolution OLED pixel array. However, the printing process suffers from critical problems associated with cross contamination, pattern uniformity, and deterioration of unique physical/photoelectric characteristics during the sequential process of pixel formation. In this regard, light-emitting organic semiconductor as a core material of OLED requires physical and chemical resistance to improve durability. In this work, we propose an OLED with differentiated technologies by implementing orthogonal polymer semiconductor gel (OPSG) conversion technology that is durable against external stimuli and maintain intrinsic photoelectric propose.

KIEEME 2020, Pyeongchang, Korea

July 8 - 10, 2020 (Wed. - Fri.), Phoenix Park

Wi-Fi Energy-Harvesting Metamaterial and Ionic Thermoplastic Polyurethance Based Wireless VOCs Sensor System

Hojin Lee (Invited Talk)

Abstract 

  Metamaterials, that possesses powerful ability to manipulate the electromagnetic (EM) waves exhibiting the unprecedented EM properties, have attracted considerable attention as new sensing platform having great sensing capability of high sensitivity, rapid sensing response, and non-destructive detection. However, conventional metamaterial based sensor systems require expensive and complicated measurement system that limits real-time application. In this paper, wireless-powered volatile organic compound (VOCs) sensor is presented by combining energy-harvesting metamaterial (EH-MM) as wireless sensing platform and ionic thermoplastic polyurethane (i-TPU) electrolyte as a VOCs sensing material. Especially, to accomplish the practical wireless-powered sensing system, proposed EH-MM based sensor is designed to operate by harvesting the widespread commercial 2.4 GHz Wi-Fi source. When i-TPU electrolyte was exposed to VOCs, diffusivity of ionic liquid increases leading to decrease in resistance of i-TPU electrolyte that can be identified with differential harvested energy level induced from resonance property variation of the EH-MM. By analyzing variation of the energy-harvesting rate as output DC voltage levels, proposed sensor system could provide sensitive and accurate VOCs sensing results without complicated analyzing system. Also, using multi-analyte sensing capability of i-TPU electrolyte, the EH-MM sensor could classify differential VOCs including toluene, hexane, ethanol, and acetone that causes harmful effects for human by simply displaying the differential output voltage levels. Furthermore, the EH-MM sensor shows fast responses (< 1 sec), wide range of VOCs concentration (> 1000 ppm) and high stability (> 1 month) in ambient condition. As a result, a novel method for designing the simple and portable VOCs sensing system is presented offering the satisfactory sensing abilities with easily accessible sensing platform. It is expected that the proposed sensor system is expected to offer new route to real-time and wireless sensor systems which make it possible for the proposed sensor to be widely used in the various sensing applications.