Asymmetric deformation in poly(ethylene-co-1-octene)/multi-walled carbon nanotube composites with glass micro-beads for highly piezoresistive sensitivity

Abstract

To develop strain sensors with excellent reliability, stability, sensitivity, reversibility, and facile processing still suffers great challenge. In this work, the glass micro-beads (μ-GB) with high modulus were added into poly(ethylene-co-1-octene)/multi-walled carbon nanotubes (POE/MWCNTs) composites to construct modulus mismatching domains, which generated asymmetric deformation in the composites during compression and then improved piezoresistive sensitivity. The μ-GBs with diameter of 45, 75, and 105 μm were used to evaluate the size effect of modulus mismatching domains on the piezoresistive sensitivity of the composites. It was very interesting to find that the composites with different diameter of μ-GBs exhibited different piezoresistive sensitivity. The highest piezoresistive sensitivity was found in the composites with the smallest size of μ-GBs (45 μm). Additionally, the piezoresistive sensitivity was also improved by increasing the content of μ-GBs. For example, the gauge factor of the POE/MWCNTs composites increased from 1.9 to 6.4 by the incorporation of 50 wt% μ-GBs with 45 μm in diameter. The mechanism of the asymmetric deformation in the composites with modulus mismatching domains under cyclic loading was discussed in detail. Furthermore, the strain sensor with μ-GBs had excellent reliability, stability and reversibility, which was attached to a sport shoe and exhibited a good cyclic signal response during walking. Besides, the Young’s modulus and compression modulus were also enhanced by the addition of μ-GBs. For example, the Young's modulus of the POE/MWCNTs composites showed 300% enhancement by adding 50 wt% μ-GBs with 45 μm in diameter.