Parasitic capacitance modeling and measurements of conductive yarns for e-textile devices

Ziqi Qu; Zhechen Zhu; Yulong Liu; Mengxia Yu; Terry Tao Ye

doi:10.1038/s41467-023-38319-6

Parasitic capacitance modeling and measurements of conductive yarns for e-textile devices

Nat Commun. 2023 May 15;14(1):2785. doi: 10.1038/s41467-023-38319-6.

Authors

Ziqi Qu^{1

2}, Zhechen Zhu^{1

3}, Yulong Liu^{1

4}, Mengxia Yu^{1

5}, Terry Tao Ye⁶

Affiliations

¹ Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
² Department of Nanotechnology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
³ Department of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA.
⁴ Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
⁵ Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore.
⁶ Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, 518055, China. yet@sustech.edu.cn.

Abstract

Conductive yarns have emerged as a viable alternative to metallic wires in e-Textile devices, such as antennas, inductors, interconnects, and more, which are integral components of smart clothing applications. But the parasitic capacitance induced by their micro-structure has not been fully understood. This capacitance greatly affects device performance in high-frequency applications. We propose a lump-sum and turn-to-turn model of an air-core helical inductor constructed from conductive yarns, and systematically analyze and quantify the parasitic elements of conductive yarns. Using three commercial conductive yarns as examples, we compare the frequency response of copper-based and yarn-based inductors with identical structures to extract the parasitic capacitance. Our measurements show that the unit-length parasitic capacitance of commercial conductive yarns ranges from 1 fF/cm to 3 fF/cm, depending on the yarn's microstructure. These measurements offer significant quantitative estimation of conductive yarn parasitic elements and provide valuable design and characterization guidelines for e-Textile devices.