Highly stretchable and sensitive piezoresistive carbon nanotube/elastomeric triisocyanate-crosslinked polytetrahydrofuran nanocomposites†
Piezoresistive polymer nanocomposites are highly desirable for flexible mechanical sensing applications. In this study, a family of multi-walled carbon nanotube (CNT)/elastomeric triisocyanate-crosslinked polytetrahydrofuran (ETC-PTHF) nanocomposites that are highly stretchable and highly sensitive to mechanical stimuli were designed, synthesized, and characterized. The CNTs in the CNT/ETC-PTHF nanocomposites were initially dispersed in the ETC-PTHF matrix uniformly, leading to a relatively high electrical conductivity. Upon stretching, both the degree of CNT alignment along the stretching direction and the degree of PTHF crystallinity increased consistently with the tensile strain. The strain-induced microstructure change adversely affected the CNT conducting pathways, thereby reducing the electrical conductivity of the nanocomposites. For instance, the electrical conductivity of the 15 wt% CNT/ETC-PTHF nanocomposites decreased by approximately 7.3%, 29.2%, and 19.76, 169.2 and 1291 times when the tensile strain was 1%, 5%, 50%, 250%, and 500%, respectively. The nanocomposite film was able to detect a mechanical stimulus (poking) weaker than the landing force of a mosquito. Furthermore, the nanocomposite film demonstrated rapid and highly sensitive responses to continuous finger motion. These new piezoresistive CNT/ETC-PTHF nanocomposites possess a number of desirable characteristics including ease of fabrication, low cost, and high sensitivity, thereby making them very promising candidates for applications in electronic skins, electronic textiles, and biomedical detectors.