Multi-scale numerical simulations on piezoresistivity of CNT/polymer nanocomposites

Bin Hu,Yuan Li,Kentaro Akagi,Tomonori Watanabe,Ning Hu,Yong Cai,Weifeng Yuan

doi:10.1186/1556-276x-7-402

Abstract

In this work, we propose a comprehensive multi-scale three-dimensional (3D) resistor network numerical model to predict the piezoresistivity behavior of a nanocomposite material composed of an insulating polymer matrix and conductive carbon nanotubes (CNTs). This material is expected to be used as highly sensitive resistance-type strain sensors due to its high piezoresistivity defined as the resistance change ratio divided by the mechanical strain. In this multi-scale 3D numerical model, three main working mechanisms, which are well known to induce the piezoresistivity of strain sensors fabricated from nanocomposites, are for the first time considered systematically. They are (a) the change of the internal conductive network formed by the CNTs, (b) the tunneling effect among neighboring CNTs, and (c) the CNTs’ piezoresistivity. Comparisons between the present numerical results and our previous experimental ones were also performed to validate the present numerical model. The influence of the CNTs’ piezoresistivity on the total piezoresistivity of nanocomposite strain sensors is explored in detail and further compared with that of the other two mechanisms. It is found that the first two working mechanisms (i.e., the change of the internal conductive network and the tunneling effect) play a major role on the piezoresistivity of the nanocomposite strain sensors, whereas the contribution from the CNTs’ piezoresistivity is quite small. The present numerical results can provide valuable information for designing highly sensitive resistance-type strain sensors made from various nanocomposites composed of an insulating polymer matrix and conductive nanofillers.

Highlights

Due to their excellent electrical properties, carbon nanotubes (CNTs) of high aspect ratio are predicted to open up a whole range of smart structural applications [1]
Based on a three-dimensional (3D) statistical resistor network model [11], we have previously considered the change of internal CNT conductive network and tunneling effect in exploring the piezoresistivity behavior of the above CNT/polymer nanocomposite strain sensors [12]
The average resistance change ratio predicted from 50 Monte Carlo simulations using our previous model [12] without considering the piezoresistivity of CNTs are shown in Figure 10 by comparing with our previous experimental results [7]

Summary

Introduction

Due to their excellent electrical properties, carbon nanotubes (CNTs) of high aspect ratio are predicted to open up a whole range of smart structural applications [1]. It has been confirmed that the conductance of a CNT could be dramatically changed by introducing a mechanical strain as a consequence of structural change (e.g., chirality change [2]). Due to this piezoresistivity of CNTs, great interest has recently been aroused in building strain sensors using CNTs themselves (either single-walled carbon nanotube (SWCNT) or multi-walled carbon nanotube (MWCNT)) [3,4,5] and incorporating them into an insulating polymer matrix [6,7,8,9], as summarized in a recent review paper [10]. The effect of the piezoresistivity of CNTs themselves is not mentioned

Methods

Results

Conclusion