Fiber Optic Sensor For Detection Research Articles

RAPTOR: A fluoroimmunoassay-based fiber optic sensor for detection of biological threats

The RAPTOR was developed to meet the need for a small, portable, easily operated biosensor for the detection of biological threats in the field. This device has evolved over a number of years to reach its current level of maturity. This paper describes details of the RAPTOR's design, including the recent upgrades to the fluidics and optics subsystems, as well as design improvements that have increased both system reliability and sensitivity. Working with these system upgrades, we also investigated biochemical methods that further improve assay sensitivity. The use of NeutrAvidin/biotin chemistry to improve immobilization of the capture antibody, coupled with use of the fluorophore Alexa Fluor 647 to label the tracer antibody, has resulted in a two- to four-fold signal enhancement. These gains, in combination with redesigned optics and instrumentation, have resulted in approximately a log-order improvement over earlier systems. These improvements are shown for an assortment of analytes of interest, including Staphylococcal enterotoxin type-B, Francisella tularensis, Bacillus anthracis, and Bacillus globigii spores.

Evanescent wave fibre optic sensor for detection of L. donovani specific antibodies in sera of kala azar patients

An easy-to-use technique for detection of antibodies specific for the parasite L. donovani in human serum sample has been developed. The method is based on an evanescent wave generated from a tapered configuration of decladded optical fibre and does not require any volumetric measurement. Tapered fibres are immobilized with the purified cell surface protein of L. donovani by covalent bonding. Treated fibres are incubated with the patient serum for 10 min followed by incubation with goat anti human IgG tagged FITC. Fluorescent intensity from the fibre has been shown to be proportional to L. donovani specific antibodies present in the test sera. Direct readings can be obtained after signal enhancement through a photomultiplier tube within 5 min. The system, when tested on 12 positive sera, did not show any false negative result. Also, no false positive result was obtained with serum samples of patients infected with leprosy, tubercolosis, typhoid and malaria, showing the specificity of the sensor and efficacy of the technique.

A Fiber Optic Ultrasonic System to Monitor the Cure of Epoxy

A fiber optic ultrasonic system is described which monitors the cure of an epoxy resin. Ultrasound is generated using a high-power optical fiber to deliver high-energy pulses of light to the prepared surface of an aluminum mold that contains the curing epoxy resin. The generated ultrasound is detected using a local fiber optic ultrasound sensor embedded in the curing epoxy resin. The system was used to measure the ultrasonic signal velocity and ultrasonic attenuation throughout the cure of a neat epoxy resin at room temperature. Similar measurements also were performed using a piezoelectric transducer for ultrasound generation and an embedded fiber optic sensor for detection, which provided verification of the results using the complete fiber optic system. The complete fiber optic system demonstrated adequate sensitivity throughout the entire cure to measure the ultrasonic signal velocity and ultrasonic attenuation.

A Fiber Optic Ultrasonic System to Monitor the Cure of Epoxy

A fiber optic ultrasonic system is described which monitors the cure of an epoxy resin. Ultrasound is generated using a high-power optical fiber to deliver high-energy pulses of light to the prepared surface of an aluminum mold that contains the curing epoxy resin. The generated ultrasound is detected using a local fiber optic ultrasound sensor embedded in the curing epoxy resin. The system was used to measure the ultrasonic signal velocity and ultrasonic attenuation throughout the cure of a neat epoxy resin at room temperature. Similar measurements also were performed using a piezoelectric transducer for ultrasound generation and an embedded fiber optic sensor for detection, which provided verification of the results using the complete fiber optic system. The complete fiber optic system demonstrated adequate sensitivity throughout the entire cure to measure the ultrasonic signal velocity and ultrasonic attenuation.

Intrinsic optical fibre sensor for monitoring acoustic emission

A novel intrinsic optical fibre sensor for detection of acoustic emission (AE) has been designed, built and tested. This sensor is intended for use in monitoring machine tool wear. An optical fibre is held between the transducer backing and the surface being probed. The coupling of AE waves through the fibre into the backing causes a phase change in the light transmitted by the fibre. This phase change is detected using a Mach-Zehnder interferometer, locked in quadrature with a phase servo. Acoustic emission during cutting is conveyed to the sensing fibre on the machine bed via either the tool or workpiece. Sensing of AE may then yield information on the state of wear of the tool.

Optical fibre sensor for detection of hydrogen cyanide in air. Part 2. Theory and design of an automatic detection system

An automatic spectrophotometric instrument is described which monitors the colour change due to the reaction of cyanogen chloride with 4-methylpyridine and pyrimidinetrione impregnated on XAD-7 resin beads by measuring the spectral absorption at 530–565 nm using a green light emitting diode with peak intensity at 560 nm. Background absorption was monitored using a red light emitting diode. Randomised fibre optic bundles were used to collect and guide the light to silicon planar photodiode detectors.

Optical fibre sensor for detection of hydrogen cyanide in air : Part 1. Reagent Characterization and Impregnated Bead Detector Performance

Hydrogen cyanide is detected by oxidation of the atmospheric sample with chloramine-T (sodium N-chloro-4-methylbenzenesulphonamide) impregnated on XAD-7 resin beads to yield cyanogen chloride. This reacts with 4-picoline (4-methylpyridine) and barbituric acid (pyrimidinetrione) also impregnated on XAD-7 beads, to yield a colour change with a maximum absorbance change around 530–565 nm. Using a modulated monochromated white light source and lock-in detector, the reagent system was able to detect HCN in air at 1 μl l −1 within 1 min. A flow- rate through the reagent cell of 60 ml min −1 air was chosen to give the best overall performance. Lifetime tests indicated a loss of 4-picoline due to evaporation, although reagent beads through which air was drawn at 100 ml min −1 for 66 h were still able to detect 10 μl l −1 HCN in less than 1 min. The method is not reversible and could not be used to monitor HCN concentration in air, but is nonetheless useful for the detection of HCN below its toxic level in a short time.