Strain sensing conductive polymer composites: Sensitivity and stability

Abstract

The effect of conductive network morphology and interfacial interaction on the strain sensing capability of conductive polymer composites (CPCs) is thought as crucial. Nevertheless, the stability in strain sensing behavior has barely been investigated. Herein, the resistivity-strain behavior in terms of stability and sensitivity of CPCs based on poly(styrene-butadiene-styrene) (SBS) containing multiwalled carbon nanotubes (MWCNTs) are studied. It is shown that the preparation method has an important influence on the resistivity-strain behavior of these CPCs. The sensitivity increases with decreasing filler content for both composites under linear uniaxial strain, showing higher strain sensitivity near the percolation threshold. A higher and wider range of sensitivities is obtained for melt mixed SBS/MWCNT. Meanwhile, resistivity downward drifting and shoulder peaks are shown for composites from melt mixing under dynamic strain. Interestingly, linear relationships and reversible resistivity in every cycle are observed for composites from solution mixing, showing good electromechanical consistency, stability and durability. From the TEM, rheology, SEM, SAXS, Raman microscopy and analytical modeling studies, the difference in morphology is thought to be responsible for such resistivity-strain behavior. As more disordered and less densely packed conductive networks in melt mixed CPCs are more easily destroyed under strain, evenly distributed and densely packed networks in solution mixed CPCs are more stable during cyclic stretching. Finally, different human motions have been detected using these CPCs, demonstrating the potential application of these CPCs as movement sensors.