Piezoresistive sensing performance of multifunctional MWCNT/HDPE auxetic structures enabled by additive manufacturing

Herein, we report the mechanical and piezoresistive sensing performance of 3D printed auxetic nanocomposite structures composed of a high-density polyethylene (HDPE) matrix and multi-walled carbon nanotubes (MWCNTs). The multifunctional performance of MWCNT/HDPE auxetic structures were measured under tensile loading. The results indicate that by varying the MWCNT content, as well as the relative density and cell topology (S-shaped, Chiral and Re-entrant) of the structure, we can achieve a tunable piezoresistive response. The results indicate that the S-shaped cellular structure possesses superior mechanical and piezoresistive characteristics, reporting a gauge factor of 7.6 at 4 wt % MWCNT loading, which is ∼300% higher than those measured for the Re-entrant and Chiral structures. We also present an empirical scaling equation that relates the structure's sensitivity factor to its relative density. The findings of this study provide useful guidelines for the design and fabrication of self-sensing smart materials and structures with tunable sensitivity.