Fabrication and characterizations of ultra-sensitive capacitive/resistive humidity sensor based on CNT-epoxy nanocomposites

An ultra-fast humidity sensor is a useful sensing node in medical monitoring and industrial processing units. In this paper, epoxy-carbon nanotubes (CNTs) nanocomposites-based humidity sensors at various CNTs concentrations were fabricated by spin coating technique. The structural and morphological properties of the prepared samples were studied by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), respectively. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the functional groups of the composites. Thin films of the synthesized nanocomposites were deposited onto the surface of interdigitated electrodes (IDEs) and humidity sensing properties were investigated at different working frequencies (0.1–1.5 kHz) in the humidity range 30–90% RH at room temperature. Additionally, response/recovery time and sensitivity of fabricated devices were also measured. The obtained experimental results revealed that CNTs concentration plays a key role in the sensing properties of the current sensors. The optimum CNTs concentration was found to be 1.0 wt% by virtue of its high sensitivity, quick capacitive response/recovery time (14 s/6 s) and resistive response/recovery time (10 s/5 s) as compared to the pristine epoxy and CNTs.