A sparse-dense hierarchical structured conductive elastomer composites for highly sensitive and stretchable strain sensor

Flexible strain sensor using conductive elastomer (CE) have fostered hope for the development of healthcare, human–machine interfaces, and soft robotics technologies. However, it is still challenging to obtain CE based strain sensor with excellent stretchability, wide strain range, high sensitivity coupled with outstanding stability via facile preparation process. Herein, combining the advantages of sparse and dense conductive network, a sparse-dense hierarchical structured conductive elastomer composites (CECs) based on natural rubber (NR) and modified MWCNTs (m-MWCNTs) is developed through facile one-pot synthesis. By means of the low cloud point of nonionic surfactant Triton x-100, the thick-sparse and thin-dense conductive layers as well as the excellent interface between hierarchical structure are formed by controlling the content of Triton x-100 and dispersed temperature. The severe slippage of sparse conductive network at small deformation and the avulsion of dense conductive network at large strain could synergistically enhance mechanical property and sensing performance of NR/m-MWCNTs CECs. Consequently, the designed stain sensor can achieve high sensitivity and linearity at a strain range of 0–200 % and 200–423 %, which are superior to most other state-of-the-art CECs strain sensors. Meanwhile, a wide range of detection (1 %-423 %), a fast response time (0.23 s), excellent repeatability, and stability are also obtained. Besides, our developed strain sensor was successfully applied in elbow pad and knee pad for monitoring human motion. In addition, NR/m-MWCNTs CECs exhibit the superior electric heating performance. The above satisfactory results reveal that our developed sparse-dense hierarchical CECs has the potential for applications in smart wearable electronics.