Long Length MWCNT/TPU Composite Materials for Stretchable and Wearable Strain Sensors

High flexibility and ultra-sensitivity of electrically conductive polymer nanocomposites attract researchers for the development of high performance strain sensors. Herein, we prepared thermoplastic polyurethane (TPU) based flexible and conductive nanocomposite strain sensors with low percolation threshold via addition of longlength multiwalled carbon nanotubes (MWCNTs). TPU nanocomposites with varying wt % of MWCNTs loading are prepared by solution mixing process. The high-speed homogenization has reduced the Van der Waals force of attraction between MWCNTs and has increased the dispersibility in TPU matrix. Scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD) techniques were used to determine the surface morphology, dispersion of MWCNTs, and structural properties of PU nanocomposites. The low percolation at 0.1 wt % and the instantaneous gauge factor of 1389 at 50 % strain (at 0.1 wt % loading) was observed for these composites. The average value of gauge factor was found to be maximum at 0-50 % strain range in case of 0.1 wt % of MWCNT loading in PU matrix. Cyclic stretch/release experiments show good recoverability and reproducibility by these nanocomposites. This study reveals the effect of long length of MWCNTs on low percolation and dynamic strain sensing performance. Their ease of fabrication and increased sensitivity make these composites appealing for high performance strain sensing device with numerous applications in human motion monitoring.

Automated summary

High flexibility and ultra-sensitivity of electrically conductive polymer nanocomposites make them attractive for high performance strain sensors. In this study, flexible and conductive nanocomposite strain sensors based on thermoplastic polyurethane (TPU) were prepared by adding long-length multiwalled carbon nanotubes (MWCNTs) with low percolation threshold. The addition of MWCNTs enhanced the dispersibility in TPU matrix and improved the strain sensing performance. The nanocomposites exhibited low percolation, high gauge factor, good recoverability and reproducibility, making them appealing for various applications in human motion monitoring.