Preparation and performance of biaxially stretched CNT-SBS/POE flexible strain sensor with a double percolation structure

Wearable flexible strain sensors have prospective application prospects in human motion monitoring, human-computer interaction, and information transmission. However, facilely manufacturing flexible strain sensors with a high sensitivity and extended sensing range remains challenging. Herein, a flexible strain sensor with a double percolation structure was prepared through simple melting mixing and biaxial stretching. To this end, carbon nanotubes (CNTs) filled styrene butadiene styrene (SBS) and polyolefin elastomer (POE) were employed as the conductive and insulating phases, respectively. The effects of biaxial stretching on sensor performance were systematically studied. During biaxial stretching, the as-obtained CNT-SBS/POE nanocomposites with double percolation structure exhibited better processing performance and stability than conventional CNT-SBS binary composites. Biaxial stretching results in better dispersion and planar orientation of CNTs in polymers, improving the sensing property of strain sensors. The optimized stretching ratio of double percolation structured composites was determined as 1.5, with 3 wt% CNT-SBS/POE sensor exhibiting high sensitivity (gauge factor = 7501.69) over a wide strain monitoring range (0–300% strain). Additionally, the flexible strain sensors could monitor physiological activities and information transmission with good reliability, thereby promising for human-machine interaction, wearable, and medical monitoring.