Regina C. Allil

Plastic optical fiber-based biosensor platform for rapid cell detection

This work presents a novel, fast response time, plastic optic fiber (POF) biosensor to detect Escherichia coli. It discloses the technique for the development, calibration and measurement of this robust and simple-to-construct POF biosensor. The probes in U-shaped format were manufactured with a specially developed device. The calibration process led to the evaluation of the sensitivity, accuracy and repeatability by using solutions of sucrose for obtaining refractive indices (RI) in the range 1.33-1.39 IR equivalent of water and bacteria, respectively. The POF probes were functionalized with antibody anti-E. coli serotype O55 and tested firstly with saline and then with bacterial concentrations of 10(4), 10(6), and 10(8) colony forming units/ml (CFU/ml). The optoelectronic setup consists of an 880 nm LED connected to the U-shaped probe driven by a sine waveform generated by the Simulink (from Matlab(®)). On the other side of the probe a photodetector generates a photocurrent which is amplified by a transconductance amplifier. The output voltage signal is read by the analog-to-digital (A/D) input of the microcontroller. In all tested concentrations, the results presented a tendency of a decrease in the output signal with time, due to the attachment of the bacteria to the POF probe and consequent increase in the RI close to the sensitive area of the fiber surface. It has been shown that the system is capable of providing positive response to the bacterial concentration in less than 10 min, demonstrating good possibilities to be commercially developed as a portable field sensor.

Optical High-Voltage Sensor Based on Fiber Bragg Grating and PZT Piezoelectric Ceramics

Electric power facilities, such as substations, rely on voltage transformers (VTs) for measurement and protection. These pieces of equipment are bulky and heavy and tend to explode, destroying nearby equipment and posing a threat to substation personnel. Optical voltage transducers offer many improvements on traditional inductive and capacitive VTs, such as linear performance, wider dynamic range, lighter weight, smaller size, and improved safety. This paper relates to the development of a high-voltage sensor system using a PZT piezoelectric crystal as a transducer and a fiber Bragg grating as a sensor for an optical VT for a 13.8-kV class. The results show that the developed sensor is capable of attaining the International Electrotechnical Commission 0.2%-accuracy class for the revenue metering system.

Detection and Monitoring of Leakage Currents in Power Transmission Insulators

An optoelectronic sensor for real-time leakage current monitoring on high-voltage (500 kV) and medium-voltage (13.8 kV) power line insulators was developed. The leakage current drives an ultrabright light-emitting diode producing an amplitude modulated light signal. The optically intensity-encoded signal is coupled to a plastic optical fiber cable and transmitted from the high potential measurement point to the remote unit in ground potential. After the demodulation, the leakage current root mean square values are concentrated in a data logger and sent to a remote station 150-km away by general packet radio service technology. Field tests at real operational conditions on coastal regions have been performed; all data collected are stored in a structured database, which can be consulted from the Internet, while a serially produced head was developed and the sensor is ready for commercialization. Since leakage current on high-voltage insulators depends on local air pollution and microclimate changes, several sensors have to be used to cover the region monitored. For this reason, research has been conducted to determine the sensor representativeness, i.e., the actual area, which can be covered by only one sensor.

Surface Plasmon Resonance and Bending Loss-Based U-Shaped Plastic Optical Fiber Biosensors

Escherichia coli (E. coli) is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being in the feces of animals and humans, its presence in water and food is used as indicator of fecal contamination. The main method for this microorganism detection is the bacterial culture medium that is time-consuming and requires a laboratory with specialized personnel. Other sophisticated methods are still not fast enough because they require sending samples to a laboratory and with a high cost of analysis. In this paper, a gold-coated U-shaped plastic optical fiber (POF) biosensor for E. coli bacteria detection is presented. The biosensor works by intensity modulation principle excited by monochromatic light where the power absorption is imposed by predominant effect of either bending loss or surface plasmon resonance (SPR), depending on the gold thickness. Bacterial selectivity is obtained by antibody immobilization on the fiber surface. The biosensor showed a detection limit of 1.5 × 103 colony-forming units (CFU)/mL, demonstrating that the technology can be a portable, fast response and low-cost alternative to conventional methodologies for quality analysis of water and food.

Detection and monitoring of leakage currents in distribution line insulators

An optoelectronic sensor for real time leakage current monitoring on high-voltage (13.8 kV) power line insulators was developed. The leakage current drives an ultra-bright green LED producing an AM light signal. The optically intensity-encoded signal is coupled to a 1-mm plastic optical fiber and transmitted from the high potential measurement point to the Remote Unit in ground potential. After the demodulation, the leakage current values are concentrated in a data logger and sent to a remote station 150 km away by GPRS technology.

Application of Fiber Bragg Grating Sensors in Power Industry

With the idea of decreasing the number of copper wires and consequently decreasing installation and operation costs, we designed a fiber optic temperature sensor for application in large generators. The objective of the system is to cover all temperature monitoring needs of an HEP that would also overcome some of the disadvantages presented by the conventional RTD (resistive temperature detector) network.

Sensitivity Analysis of Different Shapes of a Plastic Optical Fiber-Based Immunosensor for Escherichia coli: Simulation and Experimental Results

Conventional pathogen detection methods require trained personnel, specialized laboratories and can take days to provide a result. Thus, portable biosensors with rapid detection response are vital for the current needs for in-loco quality assays. In this work the authors analyze the characteristics of an immunosensor based on the evanescent field in plastic optical fibers with macro curvature by comparing experimental with simulated results. The work studies different shapes of evanescent-wave based fiber optic sensors, adopting a computational modeling to evaluate the probes with the best sensitivity. The simulation showed that for a U-Shaped sensor, the best results can be achieved with a sensor of 980 µm diameter by 5.0 mm in curvature for refractive index sensing, whereas the meander-shaped sensor with 250 μm in diameter with radius of curvature of 1.5 mm, showed better sensitivity for either bacteria and refractive index (RI) sensing. Then, an immunosensor was developed, firstly to measure refractive index and after that, functionalized to detect Escherichia coli. Based on the results with the simulation, we conducted studies with a real sensor for RI measurements and for Escherichia coli detection aiming to establish the best diameter and curvature radius in order to obtain an optimized sensor. On comparing the experimental results with predictions made from the modelling, good agreements were obtained. The simulations performed allowed the evaluation of new geometric configurations of biosensors that can be easily constructed and that promise improved sensitivity.

Development of an Optical Sensor Head for Current and Temperature Measurements in Power Systems

The development of a current and temperature monitoring optical device intended to be used in high-voltage environments, particularly transmission lines, is presented. The system is intended to offer not only measurement reliability, but to be also practical and light weighted. Fiber Bragg gratings (FBGs) are employed in the measurement of both physical parameters: the current will be acquired using a hybrid sensor head setup—an FBG fixed on a magnetostrictive rod—while a single-point temperature information is provided by a dedicated grating. An inexpensive and outdoor-suitable demodulation method, such as the fixed filter technique, should be used in order to improve the instrumentation robustness, avoiding expensive and complex auxiliary electronics. The preliminary results for laboratory tests are also discussed.

Plastic optical fiber sensors applied to electric energy industry

The Photonics and Instrumentation Laboratory (LIF) at the Universidade Federal do Rio de Janeiro is a R&D laboratory mainly involved in optical sensors applied to Energy, Oil & Gas and Biotechnology areas. This paper demonstrates some techniques used by LIF to measure, detect and monitor several physical parameters applying plastic optical fiber (POF) either as sensor or as a communication channel for telemetry. The applications to be presented include measurement of electrical current in high voltage, temperature and leakage currents over insulators. We take advantage of the POF for its high insulation property, applying them to measure electrical parameters in high voltage environment. For each example presented, it will be shown the measurement principle, laboratory tests and field application.

POF Biosensors Based on Refractive Index and Immunocapture Effect

The combat against tropical diseases is becoming an increasingly important issue in developing countries and they need to rely on readily available and rapid response diagnostic assays. The diagnostic methods for the detection of common pathogens are still time consuming, require laboratories and specialized personnel. To the effective combat of these diseases, the diagnostic needs to be fast, reliable and accurate, not only to the clinical area, but also to immediate detection of contaminants, particularly for water quality, clinical diagnosis or food security. With the development of new technologies, especially in methods based on immunological assays, one expects increased sensitivity, specificity and speed in the detection of important microorganisms for health, veterinary medicine, agriculture and industry. This advance serves as a basis for various other techniques such as the use of biosensors for the detection of pathogens. Optical biosensors offer several advantages when compared with conventional biosensors and some of these advantages are electrical passiveness, long distance sensing and electromagnetic immunity. The objective of this work is to develop three biosensor platforms based on refractive index measurement by the following techniques: surface plasmon resonance, evanescent wave and gold thin film evanescent wave techniques using a plastic optical fiber. We aimed at the best configuration of the optical setup, sensitivity, response time, a simple fabrication method, and a good specificity for Escherichia coli detection.