Comparison of Dynamic Response of Functionalized and Bare MWNT Sensors

A resistive sensing device based on functionalized multi-walled carbon nanotubes (f-MWNTs) utilizing chemical oxidation method was fabricated successfully and proved sensitive to ethanol vapor. Dielectrophoresis (DEP) manipulation was used to achieve CNTs alignment between pairs of gold microelectrodes in fabricating the CNT sensing elements. I-V characteristics were tested to ensure that the sensors operate within the linear range, i.e., no over-heat ratio was induced onto the sensing elements during operation. Upon exposure to ethanol vapor, an increase of resistance was observed in both bare MWNTs and f-MWNTs sensors. However, compared to bare MWNTs, the f-MWNTs sensors proved to have lower power consumption (i.e., as low as nano-watt level), larger responsivity and faster time response. In addition, cycling responses of the sensors were evaluated and demonstrated to have good repeatability. Moreover, resistance of both sensors would drop under applied compressed air flow, which has been utilized to clear the residual ethanol and reset the sensors to their initial condition after each cycle of measurement.