STRAIN SENSORS MADE FROM MWNT/POLYMER NANOCOMPOSITES

Extensive numerical simulation and experimental measurements have been conducted to understand the piezoresistivity characteristics and the working mechanisms of highly sensitive strain sensors made from carbon nanotubes (CNTs) embedded polymer nanocomposites. When using two kinds of multi-walled carbon nanotubes (MWNTs), it was identified that the piezoresistivity characteristics of two sensors are different. When using comparatively straight MWNTs of a large diameter, named as MWNT-7, the fundamental working mechanism of this sensor is the tunneling resistance change among CNTs due to the distance change caused by applied strains. However, for another type of MWNTs, which is of a very small diameter and seriously curved shapes, and named as LMWNT-10, the main working mechanism of the sensor may be the piezoresistivity of MWNTs themselves due to deformation of MWNTs. Furthermore, for the sensors made from MWNT-7/epoxy, further numerical and experimental investigations have been carried out to explore the effects of processing parameters and material properties on sensor sensitivity. Both numerical and experimental results indicate that a higher tunneling resistance or higher ratio of the tunneling resistance to the total resistance of the sensor leads to a higher sensor sensitivity. Processing conditions and material properties play a role in determining the sensor sensitivity.