In recent years, flexible and stretchable sensors have been a subject of intensive research to replace the traditional sensors made up of rigid metals and semiconductors. In this paper, a piezoresistive airflow sensor was designed and tested to measure the speed of air inside a pipe. Graphene/polyvinylidene fluoride nanocomposite films were prepared using a solvent-cast technique on a flexible polyethylene substrate as a piezoresistive material. Three different solutions were studied as a function of graphene concentration. The microstructure of the nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, and optical microscopy. The effect of temperature on electrical conductivity was investigated by heating and cooling the sample between the room temperature and 150 °C. The stretchability of the nanocomposite film was studied with a tensile test, and the same procedure was employed to determine the breakdown point of the electrical conductivity. The sensor response was measured in terms of the resistance change caused by air pressure and found to increase with the concentration of graphene in the composite. The sensing characteristics were simulated using the COMSOL Multiphysics software, and the modeled data were compared favorably with the experimental result. The sensitivity of the sensor was found to be 1.21% kPa −1 in the range of 0−2.7 kPa. This piezoelectric sensor possesses unique characteristics such as being lightweight, flexible, and exhibiting fast response; hence, it can have potential applications in various sectors such as ventilators, commercial HVAC, and automotive industries.

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A flexible piezoresistive sensor was developed as an accelerometer based on Graphene/PVDF nanocomposite to detect low-frequency and low amplitude vibration of industrial machines, which may be caused due to misalignment, looseness of fasteners, or eccentric rotation. The sensor was structured as a cantilever beam with the proof mass at the free end. The vibration caused the proof mass to accelerate up and down, which was converted into an electrical signal. The output was recorded as the change in resistance (response percentage) with respect to the acceleration. It was found that this accelerometer has a capability of detecting acceleration up to 8 gpk-pk in the frequency range of 20 Hz to 80 Hz. The developed accelerometer has the potential to represent an alternative to the existing accelerometers due to its compactness, simplicity, and higher sensitivity for low frequency and low amplitude applications.

In this study, the process for tuning the electrical properties of graphene/polyvinylidene fluoride (Gr/PVDF) nanocomposite films by a thermal annealing process is explored. The surface morphology and microstructure of the nanocomposite were characterized. The effect of temperature on the electrical conductivity was investigated by heating and cooling the sample from the room temperature up to 150 °C. The effect of annealing on the electrical conductivity was recorded as a function of annealing temperature. A Hall effect measurement was conducted as a function of annealing temperatures to obtain Hall voltage (V H), carrier mobility (μH), carrier concentration (n H), Hall coefficient (R H), resistivity, and carrier conductivity type (n or p). It was found that the films annealed at 150 °C exhibited the best electrical conductivity of Gr/PVDF films. This study may provide an insight into the development and utilization of Gr/PVDF films in future electronics and the potential applications in various sectors such as aerospace, automotive, and biomedical industries.

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