Electrical properties of carbon nanotube/liquid metal/rubber nanocomposites

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.