Electrical properties of carbon nanotube/liquid metal/rubber nanocomposites

Cheng Li,Jing Zhong,Liang Zhang,Hongyun Chen

doi:10.1063/5.0027021

Abstract

Carbon nanotube (CNT)/rubber nanocomposites have wide applications in wearable devices and robotics, as stretchable conductors or sensitive/flexible piezoresistive sensors. However, the modification and optimization of the electrical properties of these nanocomposites are highly dependent on the dispersion quality of CNTs, and more severally, the high dosage of CNTs could inevitably increase the modulus of rubber, which limits their interaction with soft materials, such as human tissue. A liquid metal (LM), such as eutectic gallium indium, can be considered as a soft and conductive additive to increase the conductivity of rubber. Here, we investigate the modification of the electrical and mechanical properties of CNT/rubber nanocomposites by LMs. We found that LMs are well dispersed in the rubber matrix with the average size increasing with its loading. Wrinkles formed on LM droplets, indicating that the oxide layer was subjected to compressive stress during the polymerization of rubber. Although the conductivity of the CNT/rubber nanocomposites can be improved by about 328% at 10 vol. % of LMs with negligible loss of mechanical properties, further increasing the loading of LMs would decrease the conductivity, suggesting their limited contribution for the conductive network formation in the rubber matrix.

Highlights

High performance flexible and conductive devices, which have great potential in the fields of optoelectronics, sensing, and medical treatment, have been a research hotspot since the last century
We demonstrated that Carbon nanotube (CNT)/liquid metal (LM)/rubber nanocomposites have a maximum conductivity at 10% volume fraction of LMs and increasing the content of LMs would restrict the conductive network of nanocomposites
We further investigated the piezoresistive properties of LM/CNT/rubber nanocomposites

Summary

INTRODUCTION

High performance flexible and conductive devices, which have great potential in the fields of optoelectronics, sensing, and medical treatment, have been a research hotspot since the last century. In order to obtain stretchability by a specific structure, many interesting patterns have been designed such as serpentine, meshes, and microcracks.. In order to obtain stretchability by a specific structure, many interesting patterns have been designed such as serpentine, meshes, and microcracks.5–7 These strategies generally involve with complex processing, and both are time-consuming and costly. Considering the softness of LMs, it should be very interesting to investigate the modification of the electrical and mechanical properties of CNT/rubber nanocomposites With this purpose in mind, here, we introduce a simple and feasible method to prepare stretchable and conductive nanocomposites, modified by two extremely different additives, hard CNTs and soft LMs. By changing the amount of EGaIn, the influence of LMs on the conductivity of the conductive matrix with a rubber substrate containing 1 vol % multi-walled carbon nanotubes (MWCNTs) was investigated. This suggests that the contribution for the conductive network formation in the rubber matrix by LMs is very limited

EXPERIMENTAL

AND DISCUSSION

Findings

CONCLUSIONS