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Integrating foil sensors into fibre-reinforced plastics offers the advantage of making manufacturing measurable with spatial resolution and thus simplifies quality control. One challenge here is the possible negative influence of the integrated sensors on the mechanical behaviour of the structure. This article shows how the different parts of a film sensor influence important mechanical strength parameters of fibre composites. A comparison of two thermoplastic carrier films shows that by choosing polyetherimide (PEI) instead of polyimide (PI), a considerably more advantageous failure behaviour of the composite is achieved. While integrated PI films reduce the interlaminar shear strength by 68%, no impairment is noticeable due to PEI films. For the critical energy release rate, PEI-based film sensors even lead to a significant increase, while a significant deterioration of 85% can be observed for PI-based sensors. However, not only the film substrate plays a decisive role for the interlaminar shear strength, but also the sensor structures themselves. In this article, sensor structures made of gold were investigated. The decisive parameter for the impairment seems to be the area share of gold structures in the sensor. For a sensor pattern made of gold lines with an area filling of 50%, a reduction of the interlaminar shear strength of up to 25% was observed depending on the angle between the shear stress and the gold lines. No impairment was observed for sensor structures with less gold area. The results show that PEI substrates can be a superior alternative for sensor integration into fibre composites and suggest that there is a trade-off between sensitivity and degradation of mechanical properties when designing interdigital sensors. [ABSTRACT FROM AUTHOR]

Design and development of a low-cost, low-power, miniature, highly sensitive, and selective carbon dioxide (CO2) sensor is an active research area due to the rapid rise of CO2 closed to 408 ppm in the atmosphere because of the industrial revolution. This research proposes a highly sensitive planar interdigital sensor coated with graphene oxide (GO) to induce selectivity towards CO2. The performance of the sensor has been analysed with various temperatures, humidities, and different CO2 concentrations. The developed sensor has been characterised using Electrochemical Impedance Spectroscopy (EIS). The calibration standard has been developed for a range of CO2 concentrations from 400 ppm to 4000 ppm. The standard gas chromatography (GC) method is used to validate all the results. The temperature and humidity compensation mechanisms are also included to improve the detection ability for determining the CO2 gas concentration from unknown gas samples. Repeatability, reproducibility, stability, cross-sensitivity, response, and recovery time are also tested. The obtained results are highly encouraging to develop a low-cost smart CO2 gas sensing system for both indoor and outdoor environmental applications. [ABSTRACT FROM AUTHOR]

During fiber composite production, the quality of the manufactured parts can be assured by measuring the progress of the curing reaction. Dielectric film sensors are particularly suitable for this measurement task, as they can quantify the degree of curing very specifically and locally. These sensors are usually manufactured on PI films, which can lead to delaminations after integration. Other authors report that this negative influence can be reduced by miniaturization and a suitable shaping of the sensors. This article pursues as an alternative, a novel approach to achieve a material closure instead of a geometrically generated form closure by choosing suitable thermoplastic materials. Thermoplastic films made of PEI, PES and PA6 are proposed as carrier substrates for thin film sensors. They are investigated with regard to their mechanical effects in FRP. The experiments show that the integration of PES and PEI in FRP has the best shear strength, but PA6 leads to a higher critical energy release rate during crack propagation in mode I. For PI, a locally strongly scattering critical energy release rate was observed. Neither in tensile nor in Compression After Impact (CAI) tests a significant influence of the films on these characteristic values could be proven. [ABSTRACT FROM AUTHOR]

We present a cost-efficient screen printed sensor for online cure monitoring of adhesives on semi-finished parts. It can be manufactured and used directly in the production line. A printed interdigital sensor is used for this purpose. We investigate the influence of environmental condition and modified adhesive properties on the sensor’s signal. The sensor can successfully detect insufficient curing, for example, due to excessive humidity or improper mixing ratio of binder and hardener. Therefore, our sensor will enable a cost-effective automated control of the curing of adhesives in the production lines of the factories of the future. [ABSTRACT FROM AUTHOR]

This paper addresses the optimization and implementation of a fringing field capacitive soil moisture sensor using the printed circuit board technology. It includes the analysis of a novel configuration of an interdigital sensor for measuring soil moisture with two existing configurations. The optimized designs were simulated by using a 3-D finite-element method and fabricated by using a copper clad board. The performance of the fabricated sensors was evaluated using four soil samples collected from different locations. The observations were compared with the standard gravimetric method to evaluate the soil water content of the samples. The characterization method and the results of the whole sensing system are discussed in terms of calibration, dynamic test, and repeatability. [ABSTRACT FROM AUTHOR]

During fiber composite production, the quality of the manufactured parts can be assured by measuring the progress of the curing reaction. Dielectric film sensors are particularly suitable for this measurement task, as they can quantify the degree of curing very specifically and locally. These sensors are usually manufactured on PI films, which can lead to delaminations after integration. Other authors report that this negative influence can be reduced by miniaturization and a suitable shaping of the sensors. This article pursues as an alternative, a novel approach to achieve a material closure instead of a geometrically generated form closure by choosing suitable thermoplastic materials. Thermoplastic films made of PEI, PES and PA6 are proposed as carrier substrates for thin film sensors. They are investigated with regard to their mechanical effects in FRP. The experiments show that the integration of PES and PEI in FRP has the best shear strength, but PA6 leads to a higher critical energy release rate during crack propagation in mode I. For PI, a locally strongly scattering critical energy release rate was observed. Neither in tensile nor in Compression After Impact (CAI) tests a significant influence of the films on these characteristic values could be proven.

This paper is about optimizing the geometric parameters of the interdigitated electrodes. In this paper we optimize number of electrodes, length and width of them and the distance between them, in order to determine the electrical parameters such as relative permittivity and capacitance. The finite element method COMSOL Multiphysics® software in frequency range 10Hz to 1GHz is used in order to measure the electrical impedance of biological medium and simulate the particle separation in micro channel. [ABSTRACT FROM AUTHOR]

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]

Sensor systems capable of in situ , continuous impedance measurements are expected to play an important role for a broad spectrum of applications. However, widespread use of these devices is hindered by their current form of separated sensors from bulky, expensive readout instruments. Moreover, the lack of other relevant sensing functionalities on the same system results in an incomplete understanding of the complex physical and chemical changes taking place. In this paper, a miniaturized sensor patch (MSP) with simultaneous impedance and temperature measurements and fully integrated readout is cleverly designed. By using an on-board microcontroller, sensor signal is read out locally and transmitted digitally, eliminating the noise on the signal over the transmission path. The MSP is stable over a wide temperature range (20–180 °C), and in various dielectric mediums (air, epoxies). Moreover, flexible circuit board technology based device fabrication permits further extended functionalities of the patch with off-the-shelf surface mounted devices. The MSPs were successfully applied for monitoring the polymerization processes of two epoxies, demonstrated the potential of the proposed sensor patch as an integrated and multifunctional sensing solution. [ABSTRACT FROM AUTHOR]

Bone loss and osteoporosis is a serious health problemworldwide. The impact of osteoporosis is far greater than many other serious health problems, such as breast and prostate cancers. Statistically, one in three women and one in five men over 50 years of age will experience osteoporotic fractures in their life. In this paper, the design and development of a portable IoT-based sensing system for early detection of bone loss have been presented. The CTx-I biomarker was measured in serum samples as a marker of bone resorption. A planar interdigital sensor was used to evaluate the changes in impedance by any variation in the level of CTx-I. Artificial antibodies were used to introduce selectivity to the sensor for CTx-I molecule. Artificial antibodies for CTx-I molecules were created using molecular imprinted polymer (MIP) technique in order to increase the stability of the system and reduce the production cost and complexity of the assay procedure. Real serum samples collected from sheep blood were tested and the result validation was done by using an ELISA kit. The PoC device was able to detect CTx-I concentration as low as 0.09 ng/mL. It exhibited an excellent linear behavior in the range of 0.1-2.5 ng/mL, which covers the normal reference ranges required for bone loss detection. Future possibilities to develop a smart toilet for simultaneous measurement of different bone turnover biomarkers was also discussed. [ABSTRACT FROM AUTHOR]

A low-cost, repeatability, and linearity interdigital capacitive transducer is proposed with an explanation of experimental results. The probe is in the form of a printed circuit board (PCB) with configuration of two interpenetrating comb electrodes, which is different from the configuration of the moisture content sensors available in the market and literature. The moisture contents of the tested rubber wood samples were in the range of 6–70%. The change in capacitance of sensing probe due to the change of moisture content inside rubber wood was detected by the modified bridge circuit. The performance of this sensor is 2% accuracy error with 0.98% precision error. [ABSTRACT FROM AUTHOR]

Extended research on the design and development of a smart nitrate sensor for monitoring nitrate concentration in surface and groundwater are reported in this paper. The developed portable sensing system consists of a planar interdigital sensor, associated electronics, instrumentation, and electrochemical impedance spectroscopy based analysis. The system is capable of measuring nitrate concentrations in the range of 0.01–0.5 mg/L in ground and surface water. This paper extends our earlier work by including a temperature compensation capacity within the sensor. WiFi-based Internet of Things (IoT) has been included, making it a connected sensing system. The system is capable of sending data directly to an IoT-based web server, which will be useful to develop distributed monitoring systems in the future. The developed system has the potential to monitor the impact of industrial, agricultural, or urban activity on water quality, in real time. [ABSTRACT FROM PUBLISHER]

Bone loss and osteoporosis is a serious health problem worldwide. The impact of osteoporosis is far greater than many other serious health problems, such as breast and prostate cancers. Statistically, one in three women and one in five men over 50 years of age will experience osteoporotic fractures in their life. In this paper, the design and development of a portable IoT-based sensing system for early detection of bone loss have been presented. The CTx-I biomarker was measured in serum samples as a marker of bone resorption. A planar interdigital sensor was used to evaluate the changes in impedance by any variation in the level of CTx-I. Artificial antibodies were used to introduce selectivity to the sensor for CTx-I molecule. Artificial antibodies for CTx-I molecules were created using molecular imprinted polymer (MIP) technique in order to increase the stability of the system and reduce the production cost and complexity of the assay procedure. Real serum samples collected from sheep blood were tested and the result validation was done by using an ELISA kit. The PoC device was able to detect CTx-I concentration as low as 0.09 ng/mL. It exhibited an excellent linear behavior in the range of 0.1–2.5 ng/mL, which covers the normal reference ranges required for bone loss detection. Future possibilities to develop a smart toilet for simultaneous measurement of different bone turnover biomarkers was also discussed.

ABSTRACT Interdigital sensors (IDS) have received great attention for production monitoring of polymers over the past decade. However, conventional IDS are limited by high noise to environment due to the dual side access of the sensor, low nominal capacitance, and sensitivity. In this study, a shielded IDS fabricated by flexible circuit board (FCB) technology is presented to overcome these challenges. Compared to conventional sensors, the environmental dependence of the new sensor is minimized by the copper shield. Furthermore, nominal capacitance of at least 350% higher, and an increase of sensitivity per unit area are achieved. To demonstrate the capabilities of the new IDS, a FCB comprising the proposed sensor is fabricated, attached to a mould, and successfully applied for in situ real-time production monitoring of an epoxy resin. The resulting flexible sensor is noninvasive towards the fabricated parts, and measures the key stages along the production process. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2028-2037 [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]

Composite materials are increasingly used for advanced applications subjected to high standards of quality that can be guaranteed by sophisticated control systems of the production process. Quality is usually controlled by monitoring temperature inside the laminate, but some researches have also evaluated the degree of cure during the thermal cycle. The goal of this work is to measure the local cure degree of thick laminates presenting a different trend as function of thickness; to achieve this aim, a suitable interdigital dielectric sensor was developed. Sensor development was carried out through FEM simulation, suited to evaluate the electric field inside the laminate: the depth of measurement of the sensor is due to its trend. The sensor was realized after having designed it and it was experimentally verified comparing the cure degree measured in a laminate polymerized in an oven with those recorded through a cure process simulation. A thick laminate was chosen because the cure degree trend is different as function of thickness and this condition is ideal to check if the sensor is able to perform local measurements. [ABSTRACT FROM AUTHOR]

A novel biosensor for inspection of meat in a noninvasive and nondestructive way has been fabricated and developed. The sensor has the planar interdigital structure and the consecutive fingers are connected to positive and negative electrodes, respectively. A novel sensor has been fabricated which provides improved results. The experimental results show the sensors have a great potential to estimate the fat content of meat in a noninvasive and nondestructive way. [ABSTRACT FROM PUBLISHER]