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. 2017 Mar 21:7:45013.
doi: 10.1038/srep45013.

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

Yuan-Qing Li  1 , Pei Huang  1 , Wei-Bin Zhu  1 , Shao-Yun Fu  1 , Ning Hu  1   2 , Kin Liao  3
Affiliations

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

Yuan-Qing Li et al. Sci Rep. .

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.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1
(A) Schematics of the fabrication of the wire-shaped strain sensor: (1) cotton thread, (2) CT, (3) CT with electrodes, (4) PDMS resin and (5) CT/PDMS sensor. SEM images of CTs with low (B) and high (C) magnification, and the fracture surface of CT/PDMS composite wire (D).
Figure 2
Figure 2
(A) Typical tensile stress-strain curve of the CT/PDMS composite wire, inset shows the flexibility of the composite wire. (B) The stress-strain curve of the CT/PDMS composite wire under cyclic tensile straining.
Figure 3
Figure 3
(A) Current-voltage curves of the CT/PDMS composite wire under various static strain. RCR response of the CT/PDMS composite wire with single tensile loading (B), tensile loading-unloading cycles (C), loading-hold-unloading-hold cycles (D). (E) Effect of frequency on the RCR response of the CT/PDMS composite wire. (F) Reliability test of the CT/PDMS composite wire with 2% peak strain and 1 Hz frequency, up to 2000 cycles.
Figure 4
Figure 4
Application of wire-shaped sensor in finger motion (A) and blood pulse (B) monitoring.
See this image and copyright information in PMC

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