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The on‐line concentration and temperature measurement of solutions is of great interest as a means of quality production control in many industrial processes, such as in food service industry, pharmaceuticals industry, chemical industry and environmental engineering, especially for harmful solutions or solutions that cannot be reached by the operator. This paper seeks to address these issues.

A high resolution all‐fiber multi‐parameter sensor system has been studied theoretically and experimentally. The sensor system can be used for on‐line monitoring of concentration and temperature simultaneously and dynamically. A combined long period fiber grating (CLPG) is used as the sensor head based on its resonance wavelength shifts being almost linearly with concentration and temperature, and also based on that the two applied resonance peaks have different concentration‐wavelength coefficients and different temperature‐wavelength coefficients. Two wavelength‐matched fiber Bragg gratings (FBGs) are used to convert resonance peak wavelengths of the CLPG into corresponding intensities for interrogation.

When the concentration and the temperature all fluctuate dynamically during experiments, a concentration resolution of 0.03 g/L has been achieved in the range of 0∼200 g/L, and a temperature resolution of 0.02C has been realized in the range of −20∼60C.

On‐line monitoring of concentration and temperature for solutions is a means of quality production control in biological, chemical and other many industrial processes, such as in food service industry, pharmaceuticals industry, chemical industry, and also in environmental engineering, especially for harmful solutions or solutions that cannot be reached by the operator. Optical fiber sensors have numerous advantages over traditional sensors, such as immunity to electromagnetic interference, higher stability and sensitivity, more easiness of multiplex, being competent for application in harsh environments, “smart structures” and on‐site measurements. Long period optical fiber grating sensor is the most appropriate sensor for multi‐parameter monitoring in the fields mentioned above, which has all the advantages of optical fiber sensor. Besides, optical fiber grating sensors can be used for monitoring more accurately because its signal is coded by wavelength. The all‐fiber sensor system is suitable for remote monitoring of many solutions, such as the solutions of NaCl, glucose, alcohol, and hydrocarbon.

This paper aims to focus on the development of an optical concentration sensor designed for measuring the concentration of components in solutions.

The operating principle of the developed sensor is based on the Bouguer–Lambert–Beer law. An optical measuring system using fiber optical cables was used for the practical implementation of the concentration sensor.

As a result of fiber optical cable use in the concentration sensor, the remote measurement principle was implemented, ensuring the instrument’s reliability and the reduction of operating costs.

The advantage of the proposed measuring system is that the sensitive element is maintenance-free, does not require power supply and can operate under severe industrial conditions. Using a fiber optic cable to transmit a light signal allows placing the sensitive element at a distance of several tens of meters from the electronics unit (the smart part).

This paper aims to develop ring resonator type optical sensors for high-sensitive detection of biomaterials and a solution concentration surrounding sensor devices. The sensing characteristics of a proposed device are investigated.

The proposed device structure is multi-slot ring resonator where the horizontal slots are arranged in vertical direction called as stacked multi-slot ring resonator. The ring resonator consists of silicon nitride because of several advantages such as easy integration of Si photo-detectors. A high sensitivity is expected in this structure because the slot height is precisely controlled by the thickness of stacked silicon nitride and etched silicon oxide layers. Sensing characteristics are evaluated from the simulated effective refractive index using the finite element method and sucrose solution sensing is confirmed using polydimethylsiloxane fluid channel.

In the simulation for the solution concentration sensor, the detection sensitivity is enhanced with increasing the slot height and the number of slots. On the other hand, for the biomaterial sensor such as the adsorbed antigen-antibody reaction, the sensitivity increases with decreasing the slot height. In this case, more than four times higher sensitivity is expected compared with the slot ring resonator sensor with vertical single slot and 0.1-0.2 μm slot width.

This paper presents an improved new structure of ring resonator type sensors and its optimum design parameters. The sensing characteristics are evaluated, and, for the biomaterial sensor, the sensitivity is high in comparison to the previous slot ring resonator.

This paper aims to propose and demonstrate a simple fiber optic sensor using a tapered plastic multimode fiber as a probe for measurement of calcium nitrate concentrations in de-ionized water.

The working mechanism is based on the observed increment in the transmission of the sensor that is immersed in calcium nitrate solution of higher concentration. The tapering of the plastic fiber is carried out by etching method using acetone, sand paper and de-ionized water.

Tapered fiber with diameter 0.45 mm gives the highest sensitivity of 0.028 mV/% due to better interaction between the evanescent field and the calcium nitrate solution with a good slope linearity of more than 98 per cent for a 1.07 per cent limit of detection in a straight probe arrangement. The use of calcium and nitrate ions within the sensing medium demonstrates the strong dependency of the sensor output trend on the electrolytic nature of the chemical solutions.

Demonstration of tapered plastic multimode fiber sensor probe for measurement electrolytic chemical solutions.

Design, fabricate and evaluate all-solid-state wearable sensor systems that can monitor ion concentrations in human sweat to provide real time health analysis and disease diagnosis capabilities.

A human health monitoring system includes disposable customized flexible electrode array and a compact signal transmission-processing electronic unit.

Patterned rGO (reduced-graphene oxide) layers can replace traditional metal electrodes for the fabrication of free-standing all solid film sensors to provide improved flexibility, sensitivity, selectivity, and stability in ion concentration monitoring. Electrochemical measurements show the open circuit potential of current selective electrodes exhibit near Nernst responses versus Na+ and K+ ion concentration in sweat. These signals show great stability during a typical measurement period of 3 weeks. Sensor performances evaluated through real time measurements on human subjects show strong correlations between subject activity and sweating levels, confirming high degree of robustness, sensitivity, reliability and practicality of current sensor systems.

In improving flexibility, stability and interfacial coherency of chemical sensor arrays, rGO films have been the developed as a high-performance alternative to conventional electrode with significant cost and processing complexity reduction. rGO supported solid state electrode arrays have been found to have linear potential response versus ion concentration, suitable for electrochemical sensing applications. Current sweat sensor system has a high degree of integration, including electrode arrays, signal processing circuits, and data visualization interfaces.

The purpose of this paper is to construct an array of sensors using polypyrrole–zinc oxide (PPy–ZnO) and PPy–vanadium (V; chemical formula: V₂O₅) fibers. To test responses of sensors, a central composite design (CCD) has been used. The results of the CCD technique revealed that the developed sensors are orthogonally sensitive to diacetyl, lactic acid and acetic acid. In total, 20 different mixtures of diacetyl, lactic acid and acetic acid were prepared, and the responses of the array sensors were recorded for each mixture.

A response surface regression analysis has been used for correlating the responses of the sensors to diacetyl, lactic acid and acetic acid concentrations during the gas phase in food samples. The developed multivariate model was used for simultaneous determination of diacetyl, lactic acid and acetic acid concentrations. Some food samples with unknown concentrations of diacetyl, lactic acid and acetic acid were provided, and the responses of array sensors to each were recorded.

The responses of each sensor were considered as target response in a response optimizer, and by an overall composite desirability, the concentration of each analyte was predicted. The present work suggests the applicability of the response surface regression analysis as a modeling technique for correlating the responses of sensor arrays to concentration profiles of diacetyl, lactic acid and acetic acid in food samples.

The PPy–ZnO and PPy–V₂O₅ nanocomposite fibers were synthesized by chemical polymerization. The provided conducting fibers, PPy–ZnO and PPy–V₂O₅, were used in an array gas sensor system for the analysis of volatile compounds (diacetyl, lactic acid and acetic acid) added to yogurt and milk samples.

The purpose of this paper is to report thick film environmental and chemical sensor arrays designed for deployment in both subterranean and submerged aqueous applications.

Various choices of materials for reference electrodes employed in these different applications have been evaluated and the responses of the different sensor types are compared and discussed.

Results indicate that the choice of binder materials is critical to the production of sensors capable of medium term deployment (e.g. several days) as the binders not only affect the tradeoff between hydration time and drift but also have a significant bearing on device sensitivity and stability. Sensor calibration is shown to remain an issue with long‐term deployments (e.g. several weeks) but this can be ameliorated in the medium term with the use of novel device fabrication and packaging techniques.

The reported results indicate that is possible through careful choice of materials and fabrication methods to achieve near stable thick film reference electrodes that are suitable for use in solid state chemical sensors in a variety of different application areas.

The purpose of this study was to develop flexible sensors for detection of different concentrations of bacteria, such as Pseudomonas aeruginosa and Staphylococcus aureus, in saline.

The sensors were fabricated using ink-jet printing technology and they consist of a pair of silver interdigitated electrodes printed on mechanically flexible substrates – foil and paper. In house measurement setup for testing and characterization of sensors has been developed. Structural, electrical and mechanical properties of flexible sensors have been determined and compared.

The characteristics of sensor – the resonant frequency as a function of different concentrations of each bacteria – are presented. The obtained results demonstrate different resonant frequencies for each dilution of Pseudomonas aeruginosa and Staphylococcus aureus in physiological saline.

Both sensors showed accurate measurements of bacterial count, which can be achieved with detection of resonant frequency, and this is reflective of the number of bacterial cells within a sample.

The findings suggest that the newly developed method based on measuring resonant frequency corresponds well with bacterial cell count, thus establishing a new proof-of-concept that such method can have significant applications in bacterial cell counting that are economic and easily maintained.

Fast, cost-effective, accurate and non-invasive method for detection of different bacteria from saline was developed.

For the first time, comparison between performances of flexible sensors on foil and paper for bacteria detection is demonstrated. Almost linear dependence between shift of resonant frequency of developed sensors and concentration of bacteria has been obtained.

The purpose of this paper is to describe the packaging and operation of an electronic tongue sensor. The sensor will be used in an industrial setting and the packaging needs to withstand the harsh clean‐in‐place (CIP) routines that are commonly employed. A suitable epoxy, Loctite FP4450 HYSOL, was identified from a number of packaging materials. The sensor was validated by carrying out cyclic voltammetry in a number of reference solutions including sulphuric acid solution and ferrocyanide in potassium chloride solution, which gave well‐defined reduction and oxidation peaks that could be compared with the literature. The operation of the sensor in mixtures of salt and citric acid solutions was also investigated and it was seen that by applying a carefully selected voltage window and scan rate to each electrode, the sensor could distinguish between the different mixtures. Further experimentation and the application of principle component analysis have shown the sensor to have good repeatability.

This paper concentrates on the ability of the sensor packaging to withstand a typical industrial CIP procedure. A number of packaging materials are investigated. In addition, the operation of the sensor has been investigated by using cyclic voltammetry.

One successful packaging material is Loctite 9461A&B HYSOL. Poly ether ether ketone also performs well after repeated CIP exposure. For ease of manufacture, Loctite FP4450 HYSOL is the epoxy of choice. An extensive matrix of test solutions was prepared from salt and citric acid powders. The aim was to investigate the sensor's ability to distinguish between increasing concentration levels of salt and citric acid and also to investigate how the sensor operates in mixtures of the solutions. By carefully choosing the applied voltage window and scan rate, the electrodes can distinguish between the mixtures

This research work has highlighted a robust packaging material to withstand industrial CIP procedures.

This study aims to use sensing technology to observe the learning status of learners in a teaching and learning environment. In a general instruction environment, teachers often encounter some teaching problems. These are frequently related to the fact that the teacher cannot clearly know the learning status of students, such as their degree of learning concentration and capacity to absorb knowledge. In order to deal with this situation, this study uses a learning concentration detection system (LCDS), combining sensor technology and an artificial intelligence method, to better understand the learning concentration of students in a learning environment.

The proposed system uses sensing technology to collect information about the learning behavior of the students, analyzes their concentration levels, and applies an artificial intelligence method to combine this information for use by the teacher. This system includes a pressure detection sensor and facial detection sensor to detect facial expressions, eye activities and body movements. The system utilizes an artificial bee colony (ABC) algorithm to optimize the system performance to help teachers immediately understand the degree of concentration and learning status of their students. Based on this, instructors can give appropriate guidance to several unfocused students at the same time.

The fitness value and computation time were used to evaluate the LCDS. Comparing the results of the proposed ABC algorithm with those from the random search method, the algorithm was found to obtain better solutions. The experimental results demonstrate that the ABC algorithm can quickly obtain near optimal solutions within a reasonable time.

A learning concentration detection method of integrating context-aware technologies and an ABC algorithm is presented in this paper. Using this learning concentration detection method, teachers can keep abreast of their students' learning status in a teaching environment and thus provide more appropriate instruction.