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. 2022 Mar 31;12(7):1155.
doi: 10.3390/nano12071155.

Synergistic Enhancement Properties of a Flexible Integrated PAN/PVDF Piezoelectric Sensor for Human Posture Recognition

Jiliang Mu  1 , Shuai Xian  1 , Junbin Yu  1 , Juanhong Zhao  1 , Jinsha Song  1 , Zhengyang Li  1 , Xiaojuan Hou  1 , Xiujian Chou  1 , Jian He  1
Affiliations

Synergistic Enhancement Properties of a Flexible Integrated PAN/PVDF Piezoelectric Sensor for Human Posture Recognition

Jiliang Mu et al. Nanomaterials (Basel). .

Abstract

The flexible pressure sensor has attracted much attention due to its wearable and conformal advantage. All the same, enhancing its electrical and structural properties is still a huge challenge. Herein, a flexible integrated pressure sensor (FIPS) composed of a solid silicone rubber matrix, composited with piezoelectric powers of polyacrylonitrile/Polyvinylidene fluoride (PAN/PVDF) and conductive silver-coated glass microspheres is first proposed. Specifically, the mass ratio of the PAN/PVDF and the rubber is up to 4:5 after mechanical mixing. The output voltage of the sensor with composite PAN/PVDF reaches 49 V, which is 2.57 and 3.06 times that with the single components, PAN and PVDF, respectively. In the range from 0 to 800 kPa, its linearity of voltage and current are all close to 0.986. Meanwhile, the sensor retains high voltage and current sensitivities of 42 mV/kPa and 0.174 nA/kPa, respectively. Furthermore, the minimum response time is 43 ms at a frequency range of 1-2.5 Hz in different postures, and the stability is verified over 10,000 cycles. In practical measurements, the designed FIPS showed excellent recognition abilities for various gaits and different bending degrees of fingers. This work provides a novel strategy to improve the flexible pressure sensor, and demonstrates an attractive potential in terms of human health and motion monitoring.

Keywords: PAN/PVDF; flexible pressure sensor; human posture recognition; integrated structure; synergistic piezoelectricity.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Fabrication of the PAN/PVDF composite film. (b) Schematic diagram of each functional layer. (c) Digital photograph of the FIPS. (d–f) Photographs of the FIPS under different deformations.
Figure 2
Figure 2
The conformational transition model of (a) PAN and (b) PVDF. (c) The SEM diagram of silver-coated glass microspheres. (d) The SEM cross-section image of the electrode layer of the composite film. (e) SEM diagram and (f) SEM cross-section of the PAN/PVDF composite membrane. (g,h) EDS spectrum of the PAN/PVDF composite film. (i,j) FTIR spectra of the PAN, PVDF and PAN/PVDF. (k) XRD patterns of PAN, PVDF and PAN/PVDF.
Figure 3
Figure 3
(a) Schematic illustration of the FIPS working process. (b,c) Piezoelectric output performance of the PAN composite film, PAN/PVDF composite film and PVDF composite film.
Figure 4
Figure 4
(a,b) The output voltage/current of the FIPS with forward and reverse connection modes. (c,e) The output voltage/current under different applied pressures. (d,f) The linear fitting analysis calculated from (c,e).
Figure 5
Figure 5
(a) The frequency response of the FIPS (1 Hz-2.5 Hz). (b,c) Voltage/current stability test of the FIPS (inset shows the enlarged view at 103 cycles and 104 cycles).
Figure 6
Figure 6
Application of the FIPS for human body pressure recognition. (a,c) The FIPS was placed on the finger. The output voltage of three FIPSs when the fingers are bent at (b,e) 20 degrees and (d,f) 45 degrees. (g) The FIPS output signal in three kinds of exercise states (slow walking, walking and running).
See this image and copyright information in PMC

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