Effect of Solvent on Segregated Network Morphology in Elastomer Composites for Tunable Piezoresistivity

Flexible, light-weight, and wearable electronics have significant potential for the development of Internet of Things. Flexible sensors with tunable piezoresistive properties are in high demand for various practical applications. Herein, different morphology thermoplastic polyurethane (TPU)/ carbon nanostructure (CNS) composites with segregated network are obtained by swelling the TPU powders using various solvents. The better solvent for TPU, dimethylformamide (DMF), renders the composites with 0.7 wt% CNS stronger polymer-filler interactions, resulting in significantly improved piezoresistive sensitivity at strain larger than 150%. Also the gauge factors (G(F)s) for these composites are 9.7 in the range 0-60% strain and 19.3 for 60-100% strain. In contrast, the composites with ethanol (EtOH) and tetrahydrofuran (THF) which swell less the TPU show delayed increase in piezoresistivity and G(F)s of 2.2 and 3.5 for strain up to 100%, respectively, suggesting potential applications for stretchable conductors.