Conformability of flexible sheets on spherical surfaces

Siyi Liu; Jinlong He; Yifan Rao; Zhaohe Dai; Huilin Ye; John C Tanir; Ying Li; Nanshu Lu

doi:10.1126/sciadv.adf2709

Conformability of flexible sheets on spherical surfaces

Sci Adv. 2023 Apr 21;9(16):eadf2709. doi: 10.1126/sciadv.adf2709. Epub 2023 Apr 19.

Authors

Siyi Liu¹, Jinlong He², Yifan Rao¹, Zhaohe Dai³, Huilin Ye⁴, John C Tanir¹, Ying Li², Nanshu Lu^{1

5}

Affiliations

¹ Center for Mechanics of Solids, Structures and Materials, Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, TX 78712, USA.
² Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI 53706 - 1572, USA.
³ Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
⁴ Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269, USA.
⁵ Departments of Biomedical Engineering, Electrical and Computer Engineering, and Mechanical Engineering; Texas Materials Institute; and Wireless Networking and Communications Group, The University of Texas at Austin, TX 78712, USA.

Abstract

Three-dimensional surface-conformable electronics is a burgeoning technology with potential applications in curved displays, bioelectronics, and biomimetics. Flexible electronics are notoriously difficult to fully conform to nondevelopable surfaces such as spheres. Although stretchable electronics can well conform to nondevelopable surfaces, they need to sacrifice pixel density for stretchability. Various empirical designs have been explored to improve the conformability of flexible electronics on spherical surfaces. However, no rational design guidelines exist. This study uses a combination of experimental, analytical, and numerical approaches to systematically investigate the conformability of both intact and partially cut circular sheets on spherical surfaces. Through the analysis of thin film buckling on curved surfaces, we identify a scaling law that predicts the conformability of flexible sheets on spherical surfaces. We also quantify the effects of radial slits on enhancing conformability and provide a practical guideline for using these slits to improve conformability from 40% to more than 90%.