A new strain sensor based on pure CNT films

Abstract

The use of carbon nanotubes (CNTs) as a material for construction of sensors is a promising effort. This is due to some unique characteristics of CNTs. In recent years, strain sensors built from CNT composite films have been developed. This thesis study first proposed that the piezoresistive sensitivity of CNT composite films can be limited due to the presence of one of the constituent elements in the CNT composite films, that is, surfactant. CNT films free of surfactants were thus hypothesized to have a great promise to improve piezoresistive sensitivity. The motivation of this thesis study was to explore this promise.

This thesis presents an experimental study on Single-Wall CNT (SWNT) films free of surfactants. Such SWNT films are called pure SWNT films. The study has concluded: (1) the gauge factor of one layer SWNT film is much higher than that of CNT composite film; (2) the fabrication of multilayered pure CNT films is highly possible; (3) the gauge factor of multilayered pure SWNT films (10 layers and 0.8mg/ml concentration) can reach as high as 2.59 with non-linearity of 0.89% and repeatability of 0.1%, which outperforms the strain sensor built from CNT composite films; (4) the role of surfactants is indeed restrictive to piezoresistive response, and (5) the junction theory is likely applicable to pure SWNT film sensors.

The main contributions of this thesis study are: (1) the finding of a new type of strain sensors built from pure CNT films and (2) the development of a fabrication process for multilayered pure SWNT films.