High-performance flexible strain sensors prepared by biaxially stretching conductive polymer composites with a double-layer structure

In this work, a high-performance flexible strain sensor was fabricated by biaxial stretching, based on conductive polymer composites (CPCs) with a double-layer structure (DLS) consisting of carbon nanotubes (CNTs)/thermoplastic polyurethane (TPU) and neat TPU. The results show that the DLS design improved the processability of the CPCs during biaxial stretching. The biaxial stretching process reduced the electrical conductivity of the CPCs as a result of the reorganized conductive pathway, while improving the sensing performance of the sensors due to the enhanced dispersion and planar orientation of the CNTs. The resulting 1 wt% DLS sensor (average CNT content = 0.5 wt% in this sensor) prepared with a stretching ratio (SR) of 2.0 shows a wide detectable strain range (0-420%), high sensitivity (GF = 102,571.8), and good stability (1600 cycles). This study provides an important strategy for the development of low-cost and high-performance flexible strain sensors by efficient biaxial stretching and structural design.