Citation: Mu, J.; Xian, S.; Yu, J.; Zhao,
J.; Song, J.; Li, Z.; Hou, X.; Chou, X.;
He, J. Synergistic Enhancement
Properties of a Flexible Integrated
PAN/PVDF Piezoelectric Sensor for
Human Posture Recognition.
Nanomaterials 2022, 12, 1155. https://
doi.org/10.3390/nano12071155
Academic Editors: Ki-Hyun Kim and
Deepak Kukkar
Received: 8 March 2022
Accepted: 29 March 2022
Published: 31 March 2022
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Article
Synergistic Enhancement Properties of a Flexible Integrated
PAN/PVDF Piezoelectric Sensor for Human
Posture Recognition
Jiliang Mu *, Shuai Xian, Junbin Yu, Juanhong Zhao, Jinsha Song, Zhengyang Li, Xiaojuan Hou, Xiujian Chou
and Jian He *
Science and Technology on Electronic Test and Measurement Laboratory, North University of China,
Taiyuan 030051, China; xianyu0279@163.com (S.X.); yujunbin@nuc.edu.cn (J.Y.);
zhaojuanhong2022@163.com (J.Z.); jinsha2006daxue@163.com (J.S.); 18222586812@163.com (Z.L.);
houxiaojuan@nuc.edu.cn (X.H.); chouxiujian@nuc.edu.cn (X.C.)
* Correspondence: mujiliang@nuc.edu.cn (J.M.); drhejian@nuc.edu.cn (J.H.)
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; integrated structure; synergistic piezoelectricity; flexible pressure sensor;
human posture recognition
1. Introduction
Wearable electronics, especially the flexible pressure sensor, have great potential
applications in the field of internet of things for personalized identification, medical research
and human-computer interaction [
1
–
5
]. For the flexible wearable pressure sensor, its
stability and reliability largely depend on the capability of the external power supply.
A traditional power supply using a battery is limited by the compatibility of the rigid
materials with skin, the charge decay over a long duty time, and it cannot be widely used
in wearable electronics [
6
]. To overcome these limitations, a self-powered piezoelectric
nanogenerator (PENG) [
7
,
8
] (all the abbreviations in this article are listed in Table S1), has
been rising and becoming the main equipment for sustainable, wearable energy collection,
and can effectively convert mechanical energy into electrical energy [
9
,
10
] and realize its
self-powered work [
11
]. Based on this, it has been used for monitoring and identifying
various posture movements of the human body [12].
There remains a challenge for piezoelectric devices to balance flexibility and electrome-
chanical conversion capability [
13
,
14
]. In order to monitor human posture, the electrical
output of wearable electronic devices should be easily obtained and observed [
15
]. Hence,
Nanomaterials 2022, 12, 1155. https://doi.org/10.3390/nano12071155 https://www.mdpi.com/journal/nanomaterials
