Effect of ZnO Doping on the Humidity Sensing Properties of the PVDF/PVA Polymeric Blend Films

Resistive humidity sensors based on PVDF/PVA polymeric blend films doped with ZnO nanoparticles were investigated in this work. The polymeric blends were prepared by solution mixing PVDF and PVA with different (0, 1, 3, 5, and 8) weight ratios of ZnO NPs. The undoped and doped PVDF/PVA blend films were deposited on the interdigitated ITO/glass electrodes to fabricate the resistive humidity sensors. The techniques of X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and contact angle were utilized to characterize the crystal structure, functional groups, surface morphology, and hydrophilicity of the undoped and doped PVDF/PVA sensing films. The sensing properties of the resistive humidity sensor based on the undoped and doped PVDF/PVA polymeric blend were examined by investigating the resistance change with relative humidity level (RH%) ranging from 20 to 90% at room temperature. By increasing ZnO NPs wt %, the sensitivity, response, and recovery times of the humidity sensor based on PVDF/PVA blend films showed an improvement due to the increased porosity and hydrophilicity of the sensing films. The sensor’s sensitivity ratio is enhanced from 4076 to 8073 by increasing the weight ratio of ZnO NPs from 0 to 8 wt %. Also, the response and recovery times are affected by increasing ZnO NPs from 0 to 8 wt %, which decreased from 28 to 18 s and 42 to 30 s, respectively.