Moore and More ›› 2025, Vol. 1 ›› Issue (4): 300-317.DOI: 10.1007/s44275-024-00019-8

• Original Article •     Next Articles

Optimizing bendability of flexible electronic devices using a neutral layer strategy

Majiaqi Wu1,2, Maoliang Jian2, Jianhua Zhang2, Lianqiao Yang2   

  1. 1. School of Microelectronics, Shanghai University, Shanghai, 201800, China;
    2. Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai, 200072, China
  • Received:2024-09-02 Revised:2024-11-21 Accepted:2024-11-26 Online:2025-11-29 Published:2025-01-08
  • Contact: Jianhua Zhang,E-mail:jhzhang@oa.shu.edu.cn;Lianqiao Yang,E-mail:yanglianqiao@i.shu.edu.cn
  • Supported by:
    This research was financially supported by the Natural Science Foundation, China (Grant No. 52175512) and Huawei Technologies Co., Ltd.

Optimizing bendability of flexible electronic devices using a neutral layer strategy

Majiaqi Wu1,2, Maoliang Jian2, Jianhua Zhang2, Lianqiao Yang2   

  1. 1. School of Microelectronics, Shanghai University, Shanghai, 201800, China;
    2. Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai, 200072, China
  • 通讯作者: Jianhua Zhang,E-mail:jhzhang@oa.shu.edu.cn;Lianqiao Yang,E-mail:yanglianqiao@i.shu.edu.cn
  • 作者简介:Majiaqi Wu (1996-), from Ningbo, Zhejiang Province. Doctoral candidate. He received his Master’s degree from Shanghai University, China in 2023. His main research interest is inorganic thin film materials.
    Maoliang Jian (1997-), from Xinyang, Henan Province. Doctoral candidate. He received his Bachelor’s degree from Shanghai Maritime University, China in 2019. His main research interests are thermal management and the reliability of power devices.
    Jianhua Zhang (1972-), from Hefeng, Hubei Province. Professor, Doctoral supervisor. She received her Ph.D. from Shanghai University, China in 1999. Her research interests include new AMOLED display, flexible display, and thin film encapsulation, thin film transistor display, and sensing.
    Lianqiao Yang (1979-), from Baoding, Hebei Province. Professor, Doctoral supervisor. She received her Ph.D. from Myongji University, Korea in 2009. Her research interests include thermal management and reliability of power semiconductor devices, advanced optoelectronic materials, and device fabrication.
  • 基金资助:
    This research was financially supported by the Natural Science Foundation, China (Grant No. 52175512) and Huawei Technologies Co., Ltd.

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Abstract: The neutral layer (NL) strategy is a key technique for improving the bendability of flexible electronic devices. In this study, by considering a three-layer structure as an example, the results obtained by finite element analysis (FEA) showed that the NL gradually moved to the top surface of the film as the film thickness and Young’s modulus increased, which are similar to the results produced by theoretical calculations. Subsequently, we optimized the thickness of a single NL structure and the failure bending radius of an indium tin oxide (ITO) electrode was reduced by 50% after optimization. In order to address the problems that affect the design of a single NL, we used optical clear adhesive (OCA) to generate multiple NLs. The FEA method was again applied to the structure and the results showed that decreasing the elastic modulus of the OCA and film thickness could reduce the maximum strain in the film. Finally, the effects of the OCA parameters on the protection of a multiple-layer ITO electrode structure were verified in bending experiments, which showed that the strain on ITO could be reduced from 5.6% to almost 0 in the two-electrode structure. The proposed strategies for designing single and multiple NLs can provide some guidance to facilitate optimizing the electronic infrastructure of flexible devices.

Key words: Flexible electronic devices, Thickness optimization design, Multiple neutral layers, Mechanical simulation

摘要： The neutral layer (NL) strategy is a key technique for improving the bendability of flexible electronic devices. In this study, by considering a three-layer structure as an example, the results obtained by finite element analysis (FEA) showed that the NL gradually moved to the top surface of the film as the film thickness and Young’s modulus increased, which are similar to the results produced by theoretical calculations. Subsequently, we optimized the thickness of a single NL structure and the failure bending radius of an indium tin oxide (ITO) electrode was reduced by 50% after optimization. In order to address the problems that affect the design of a single NL, we used optical clear adhesive (OCA) to generate multiple NLs. The FEA method was again applied to the structure and the results showed that decreasing the elastic modulus of the OCA and film thickness could reduce the maximum strain in the film. Finally, the effects of the OCA parameters on the protection of a multiple-layer ITO electrode structure were verified in bending experiments, which showed that the strain on ITO could be reduced from 5.6% to almost 0 in the two-electrode structure. The proposed strategies for designing single and multiple NLs can provide some guidance to facilitate optimizing the electronic infrastructure of flexible devices.

关键词: Flexible electronic devices, Thickness optimization design, Multiple neutral layers, Mechanical simulation

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