A multilayered flexible piezoresistive sensor for wide-ranged pressure measurement based on CNTs/CB/SR composite
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ua Wang, Zhiguang Sun, Yue Wang, Ping Liu, and Caixia Liu School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, People’s Republic of China (Received 30 January 2015; accepted 12 May 2015)
To optimize the structure of the flexible piezoresistive sensor based on conductive polymer composite and widen the workable pressure range, a piezoresistive sensor with a multilayered structure based on carbon nanotubes/carbon black/silicone rubber conductive composite was designed and investigated. Different from the traditional monolayer structure, this novel multilayered sensor consisted of three microstructured piezoresistive composite films. The experimental data showed that the electrical resistance of the sensor varied regularly with a wide range of applied pressure (0–1.8 MPa at least). The high sensitivity, high flexibility, facile fabrication, and low cost were also the advantages of this pressure sensor. In addition, the piezoresistive mechanism was studied and shown to be the synergistic effects of the contact resistance mechanism and bulk resistance mechanism. Factors influencing the piezoresistive properties were also investigated. Moreover, the consecutive loading tests verified the feasibility and stability to use this sensor element for pressure measurement.
I. INTRODUCTION
Electronic skins, which are used in wearable electronics, prosthetic limbs, robotic skins, and more other application areas, possess a high degree of flexibility and stretchability, and can sense pressure, shear, strain, temperature, humidity, fluid flow, and so on.1–6 A lot of research focuses on the electronic skin systems based on resistive, capacitive, and piezoelectric.7–9 Recently, flexible composites with piezoresistive properties have been proved to be a good choice since these materials are able to reproduce the tactile sense and fit the shape of the robot structure, obtaining the high conformability required to mimic the human skin and being able to obtain metrical information with high precision and high resolution.10,11 Composites containing dispersed conductive fillers in an insulating matrix have been studied for flexible force sensor applications.12,13 Particularly, conductive polymer composites containing carbon-based fillers have received considerable attention because of their high conductivity, low density, ease of processing, and so on.14–18 There are mainly four types of carbon fillers used: carbon black (CB), graphite (G),
Contributing Editor: Mauricio Terrones a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.160 J. Mater. Res., Vol. 30, No. 12, Jun 28, 2015
carbon fiber (CF), and carbon nanotubes (CNTs).19,20 Some polymer-based composites containing two different carbon fillers (e.g., CF and CB, CNTs and G) have also been investigated, which led to synergistic effects on network formation in the inner of the composite and improved the piezoresistive properties.21,22 Although the flexible composites have shown many advantages, low sensitivity, slow respo
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