Flexible wire-shaped strain sensor from cotton thread for human health and motion detection

Yuan-Qing Li,Shao-Yun Fu,Ning Hu,Pei Huang,Kin Liao,Wei-Bin Zhu

doi:10.1038/srep45013

Yuan-Qing Li, Shao-Yun Fu + Show 4 more

Open Access

https://doi.org/10.1038/srep45013

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Abstract

In this work, a wire-shaped flexible strain sensor was fabricated by encapsulating conductive carbon thread (CT) with polydimethylsiloxane (PDMS) elastomer. The key strain sensitive material, CT, was prepared by pyrolysing cotton thread in N2 atmosphere. The CT/PDMS composite wire shows a typical piezo-resistive behavior with high strain sensitivity. The gauge factors (GF) calculated at low strain of 0–4% and high strain of 8–10% are 8.7 and 18.5, respectively, which are much higher than that of the traditional metallic strain sensor (GF around 2). The wire-shaped CT/PDMS composite sensor shows excellent response to cyclic tensile loading within the strain range of 0–10%, the frequency range of 0.01–10 Hz, to up to 2000 cycles. The potential of the wire senor as wearable strain sensor is demonstrated by the finger motion and blood pulse monitoring. Featured by the low costs of cotton wire and PDMS resin, the simple structure and fabrication technique, as well as high performance with miniaturized size, the wire-shaped sensor based on CT/PDMS composite is believed to have a great potential for application in wearable electronics for human health and motion monitoring.

Highlights

In this work, a wire-shaped flexible strain sensor was fabricated by encapsulating conductive carbon thread (CT) with polydimethylsiloxane (PDMS) elastomer
As indicated in Fig. 1(A), CTs are prepared by directly heating the cotton thread at 800 °C for 1 h in N2 atmosphere
The slope of the RCR-strain curve at higher strains is obviously larger than that at lower strains, and the gauge factors (GF) calculated within the strain range of 8–10% is 18.5. These results indicate that the sensitivity of the carbon thread/polydimethylsiloxane (CT/PDMS) composite wire fabricated is 4 and 9 (8–10% strain) times more sensitive than conventional metallic strain gauge (GF around 2)

Summary

Introduction

A wire-shaped flexible strain sensor was fabricated by encapsulating conductive carbon thread (CT) with polydimethylsiloxane (PDMS) elastomer. We describe the fabrication of a wire-shaped strain sensor using cotton thread as raw material. The strain sensor composes of a flexible and piezo-resistive carbon thread/polydimethylsiloxane (CT/PDMS) composite wire connected with two copper wires as electrodes.

Results

Conclusion