A novel strain sensor using carbon nanotubes-organic semiconductor matrix composite on polymeric substrates

In this study, strain sensors consisting of a pentacene-carbon nanotubes (CNTs) composite layer are fabricated on flexible substrates, Kapton polyimide films, employing Wheatstone bridge configuration. The sensors were characterized with bending at 45° with respect to the bridge bias direction for two different bending radii of 50, and 40mm that corresponds to strains of 1, and 1.25 %, respectively. It was noted that the output signal of the sensors is substantially enhanced with the addition of CNTs, resulting from the improvement in conductivity of the sensing active layer. This strain sensor using CNTs-organic semiconductor matrix composite as the active layer fabricated on flexible substrates is expected to possess better reliability as compared with conventional metallic foils and inorganic semiconductor strain sensors because of their low Young's modulus (~5GPa). For instance, the high Young's modulus of micro crystalline silicon (~200GPa) limits its applications for sensors when fabricated on polymeric substrates due to the large modulus mismatch between them.