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Highlights • A novel keratin biopolymer based capacitive humidity sensor has been fabricated with two electrodes, interdigtated and rectangular spiral electrodes. • The response time of these sensors are reasonably fast, for interdigtated and spiral electrodes, the response time is about 36 s and 30 s respectively. • The recovery time is about 55 s and 51 s, respectively. The present research indicates that keratin sensing material is an appropriate candidate for humidity sensing application. Abstract This paper discusses and compares two planar capacitive humidity sensors with interdigitated and rectangular–spiral shaped. The sensors electrodes are covered by the material under test. In our case, the sensitive element of the sensor based on wool keratin polymer is elaborated in our laboratory. The morphological and structural characteristics of keratin thin film were analyzed by scanning electron microscopy, optic profilometer, Fourier transform infrared spectroscopy, X-ray diffraction and contact angle measurement. The obtained keratin films are highly hydrophilic, porous and rough surface. Humidity measurement results are presented, in particular sensitivity, hysteresis and response time. In conclusion, the fabricated sensors show very high sensitivity and small hysteresis, the highest sensitivity value is achieved by spiral electrodes. The porous and rough surface morphology and low-cost, indicate that keratin sensing material is the appropriate candidate for humidity sensing application. [ABSTRACT FROM AUTHOR]

Dielectric analysis has attracted great attention in recent years for the monitoring of composite production processes because of its capability to be applied in situ and in real-time. However, to progress from lab to industry level, the sensor system should be as sensitive and reliable as possible, whereas its fabrication should be simple and cost effective. In this study, a dielectric sensor system based on interdigital electrodes was developed. The system was fabricated by flexible circuit board technology, which combines low cost per unit area and high extendibility with off-the-shelf electronic components. The sensor’s geometry was optimized through analytical expressions and finite element method to maximize its sensitivity. Four-wire interconnects were simultaneously fabricated with the sensor to minimize the measurement error. A system with a signal-to-noise ratio better than 55 dB was successfully applied to monitor the production of glass fibre reinforced composites fabricated by vacuum assisted resin infusion process. The obtained data clearly shows the different key stages along the production process, proving the potential of the system. [ABSTRACT FROM AUTHOR]