A carbon nanotube/polymer strain sensor with linear and anti-symmetric piezoresistivity

In this article, a strain sensor made from an epoxy-based nanocomposite using a kind of multi-walled carbon nanotubes (MWNTs), i.e., LMWNT-10, was investigated. It was found that the piezoresistivity of this strain sensor is linear and anti-symmetric in tensile and compressive states within a large strain range, which is different from that of the strain sensor using another type of MWNTs, i.e., MWNT-7, in our previous reports. This linear and anti-symmetric piezoresistivity is very suitable for practical sensor applications. In our experiments, both static and dynamic responses of the two sensors were measured. The experimental results indicate that the completely different piezoresistivity characteristics of the two sensors are probably due to the complete different working mechanisms. For the sensor made from LMWNT-10, the present experimental investigations reveal that its working mechanism should be the piezoresistivity of MWNTs due to deformation of MWNTs. On the other hand, for the strain sensor made from MWNT-7, the dominant working mechanism of this sensor is the tunneling effect caused by the distance changes among carbon nanotubes.