Flexible capacitive pressure sensor based on warp knitted spacer fabric

Publication Date

10-1-2024

Document Type

Article

Publication Title

Sensors and Actuators A: Physical

Volume

376

DOI

10.1016/j.sna.2024.115602

Abstract

The demand for flexible and soft textile sensors increased due to the advancements in wearable electronic devices. Over the past decade, the focus has been on developing flexible wearable pressure sensors, which have gained significant attention. Apart from their sensing capabilities, these textile sensors offer unique advantages in human health display, such as being lightweight, portable, high elasticity, fast response time under different compression frequencies and strains, and compatibility with human skin. This study utilized polyester spacer fabrics, with various thicknesses ranging from 3 to 20 mm, as a dielectric layer and an electrically conductive layer made from graphite using a printing method to create a fabric-based capacitive pressure sensor. The surface resistance of the spacer fabric was calculated by measuring the electrical resistance of the fabrics along their length after applying the conductive paste. The findings indicated that the surface resistance decreased with the percentage of graphite in the printing paste. Specifically, a printing paste containing 60 % ethylene vinyl acetate by weight of graphite resulted in a surface resistance of around 960 Ω.m, in comparison a paste containing 80 % ethylene vinyl acetate by weight of graphite led to surface resistance levels of 48–80 Ω.m. Results showed that the initial capacity of the sensor varies depending on the thickness ratio per permittivity of the dielectric layer. Thus, the divergence between the capacitor capacity caused by physical alterations and the initial capacity has been utilized to observe changes in the capacitor's capacity. The flexible pressure sensors developed in this study showed a sensitivity of 60–240 × 10−3 kPa−1 for different applied pressures, making them more sensitive than many other pressure sensors described in existing literature. This increased sensitivity can be attributed to the low (ɛe/d) ratio and the high thickness of the spacer layer employed in the experiment. Research indicates that the electrical conductivity of the conductive layer and spacer fabric dielectric work exceptionally well together to prepare the flexible capacitive pressure sensor.

Keywords

Capacitor capacity, Dielectric layer, Fabric capacitor, Flexible pressure sensor, Spacer fabric

Department

Mechanical Engineering

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