A novel route towards tunable piezoresistive behavior in conductive polymer composites: Addition of insulating filler with different size and surface characteristics

The morphology of conductive network and their interfacial interaction with polymer matrix is thought as the key influential issues for the pressure/strain sensing behavior of conductive polymer composites (CPCs). The surface characteristics and size of these secondary insulating fillers should significantly influence the pressure/strain sensing behavior due to its influence on the morphology of conductive network and interfacial interaction between filler and polymer matrix. Herein, insulating SiO2 with different size and surface characteristics are incorporated into carbon black (CB)/silicon rubber (SR) composites to modify its piezo-resistive behavior. The conductivity of CB/SiO2/SR composites with nanoscale and hydrophobic SiO2 changes by several orders of magnitude, with more linear proportional to applied pressure and better stability under long term cyclic pressure due to better dispersion and stronger interfacial interaction. Through such simple method, high-performance piezo-resistive sensors could be fabricated with reversible piezo-resistivity, large pressure application (pressure below 2500 kPa) and tunable piezo-resistive sensitivity.