Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Mechanical and Optical Characteristics of Transparent Stretchable Hybrid Substrate using PDMS and Ecoflex Material

PDMS-Ecoflex 하이브리드 소재를 이용한 투명 신축성 기판의 기계적 및 광학적 특성

  • Lee, Won Jae (Graduate School of Nano IT Design Fusion, Seoul National University of Science and Technology) ;
  • Park, So-Yeon (Department of Materials Science and Engineering, Seoul National University of Science and Technology) ;
  • Nam, Hyun Jin (Dept. Of Manufacturing System and Design Engineering, Seoul National University of Science and Technology) ;
  • Choa, Sung-Hoon (Graduate School of Nano IT Design Fusion, Seoul National University of Science and Technology)
  • 이원재 (서울과학기술대학교 나노IT디자인융합대학원) ;
  • 박소연 (서울과학기술대학교 신소재공학과) ;
  • 남현진 (서울과학기술대학교 일반대학원) ;
  • 좌성훈 (서울과학기술대학교 나노IT디자인융합대학원)
  • Received : 2018.12.01
  • Accepted : 2018.12.28
  • Published : 2018.12.31
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Abstract

In the stretchable electronic devices, the stretchable substrate is a very essential material which determines the stretchability, performances and durability of the stretchable electronic devices. In particular, the current stretchable materials have hysteresis making difficult to used as sensors and other electronic devices. In this study, we developed a PDMS-Ecoflex hybrid stretchable substrate mixed with PDMS and Ecoflex material in order to increase stretchability and improve hysteresis characteristics. Mechanical behavior of the hybrid substrate was evaluated using a tensile test, and optical transmittance of the hybrid substrate was also measured. As the content of Ecoflex increases, the PDMS-Ecoflex hybrid substrate becomes more flexible, and the elastic modulus decreases. In addition, the PDMS substrate failed a tensile strain of 270%, while the PDMS-Ecoflex hybrid substrate did not fail even at 500% strain indicating excellent stretchability. In the repeated tensile test, the hybrid substrate with 2:1 mixing ratio of PDMS and Ecoflex showed hysteresis. On the other hand, in the case of the hybrid substrate with the mixing ratio of 1:1, hysteresis did not occur at a strain of 50% and 100%. Hence, we developed a stretchable substrate with over 150% stretchability and no hysteresis characteristics. The optical transmittance of the Ecoflex substrate was 68.6%, whereas the transmittances of the hybrid substrate with mixing ratio of 2:1 and 1:1 were 78.6% and 75.4%, respectively. These results indicate that the PDMS-Ecoflex hybrid substrate is a potential candidate for a transparent stretchable substrate.

신축성 기판은 신축성 전자소자의 신축성, 공정성, 내구성을 결정하는 매우 중요한 소재로서 신축성 전자소자를 개발함에 있어서 우선적으로 고려해야 된다. 특히 현재 사용되는 신축성 기판은 히스테리시스가 존재하여 센서 및 기타 응용에 많은 어려움이 있다. 본 연구에서는 신축성 소재 기판으로 사용되는 PDMS와 Ecoflex를 혼합한 PDMS-Ecoflex 하이브리드 신축성 기판을 제작하여 신축성과 히스테리시스 특성을 향상하고자 하였다. 인장 시험을 통하여 신축성 하이브리드 기판의 기계적 거동을 관찰하였으며, 투과도 측정을 통하여 투과도를 평가하였다. Ecoflex의 함량이 증가할수록 하이브리드 신축성 기판은 더 유연해지며, 탄성계수는 감소한다. 또한 PDMS 기판은 270% 변형률에서 파단이 발생한 반면, PDMS-Ecoflex 하이브리드 기판은 500%의 변형률까지 파단되지 않으며 우수한 신축성을 갖는 것을 알 수 있었다. 반복 인장시험에서 PDMS와 Ecoflex의 혼합비를 2:1로 제작된 기판은 히스테리시스가 발생하였다. 반면 1:1의 혼합비로 제작된 기판의 경우 50%, 100%의 변형률에서는 히스테리시스가 발생하지 않았다. 결론적으로 500% 이상의 신축성을 갖으면서 히스테리시스가 없은 기판을 제작하였다. 기판의 혼합비에 따른 광투과도 측정 결과, Ecoflex 기판의 투과도는 68.6% 이였으나, PDMS-Ecoflex 함량이 2:1, 1:1인 하이브리드 기판의 경우, 각각 78.6%, 75.4%의 투과율을 보이며, 향후 투명 신축성 기판으로서 개발 가능성을 보여주었다.

Keywords

MOKRBW_2018_v25n4_129_f0001.png 이미지

Fig. 1. Stress-strain curves of PDMS-Ecoflex 0030 mixed with different mixing ratio.

MOKRBW_2018_v25n4_129_f0002.png 이미지

Fig. 2. Elastic modulus as a function of Ecoflex 0030 mixing ratio.

MOKRBW_2018_v25n4_129_f0003.png 이미지

Fig. 3. Strain-stress curves of PDMS substrate with different strains (a) 50% strain (b) 100% strain, and (c) 150% strain.

MOKRBW_2018_v25n4_129_f0004.png 이미지

Fig. 4. Strain-stress curves of PDMS-Ecoflex hybrid substrate with different strains (mixing ratio of PDMS to Ecoflex 0030 of 2 to 1) (a) 50% strain (b) 100% strain, and (c) 150% strain.

MOKRBW_2018_v25n4_129_f0005.png 이미지

Fig. 5. Strain-stress curves of PDMS-Ecoflex hybrid substrate with different strains (mixing ratio of PDMS to Ecoflex 0030 of 1 to 1) (a) 50% strain (b) 100% strain, and (c) 150% strain.

MOKRBW_2018_v25n4_129_f0006.png 이미지

Fig. 6. Strain-stress curves of Ecoflex 0030 substrate with different strains (a) 50% strain (b) 100% strain, and (c) 150% strain.

MOKRBW_2018_v25n4_129_f0007.png 이미지

Fig. 7. The optical transmittance of PDMS-Ecoflex hybrid substrate with different mixing ratio.

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